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  • 1995-1999  (647)
  • 1998  (647)
  • Theoretical, Physical and Computational Chemistry  (583)
  • Computed tomography
  • Nuclear reactions
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Years
  • 1995-1999  (647)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Diseases of the colon & rectum 41 (1998), S. 1023-1028 
    ISSN: 1530-0358
    Keywords: Diverticulitis ; Computed tomography ; Hospital costs ; Complications ; Surgery ; Accuracy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract PURPOSE: The purpose of this study was to evaluate the use and timing of computed tomography in the treatment of patients with acute left-sided diverticulitis. METHODS: We reviewed our four-year experience of 47 patients with the diagnosis of acute diverticulitis. We have evaluated the benefits of admissionvs. delayed computed tomography in patients with this diagnosis. RESULTS: Of the 47 patients, 17 were diagnosed on clinical grounds alone, treated, and released. Thirty patients had their clinical diagnoses of diverticulitis evaluated with either computed tomographic scan (26) or laparotomy (4). Eleven of those 30 (36 percent) patients were found to have normal computed tomographic scans, indicating inaccurate clinical diagnosis, and all patients who underwent laparotomy had the pathologic diagnosis of diverticulitis. Six of the 47 patients had abscesses, but only 2 were identified at the time of admission. The remaining four abscesses were identified on delayed computed tomographic scans after failure of medical therapy. Thirty-seven hospital days were used by patients with inaccurate diagnoses before their computed tomographic scans. Analysis of cost revealed that a computed tomographic scan for all 47 patients would have cost less than the expense of admission for just the 11 patients who had normal computed tomographic scans. CONCLUSION: Routine admission computed tomographic scan for patients with acute diverticulitis leads to more accurate diagnosis, earlier identification of complications, and possible decreased hospital costs.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1534-4681
    Keywords: Hepatic metastases ; Colorectal ; Computed tomography ; Pulmonary metastases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Hepatic resection is the standard treatment for hepatic colorectal metastases. The lung represents the next most likely site, after the liver, of metastatic disease. Computed tomography (CT) of the chest is more sensitive than is chest x-ray in detecting metastatic lung lesions. However, the usefulness of chest CT in the evaluation of patients before hepatic resection remains uncertain. Methods: One hundred consecutive patients with negative chest x-rays and potentially resectable hepatic colorectal metastases underwent chest CT. Patients with CT findings suggestive of meta-static disease were subjected to thoracotomy or video-assisted thoracic surgery (VATS) before laparotomy and attempted hepatic resection. The operative findings and clinical course were analyzed. Results: Eleven of 100 patients had a positive chest CT. Four of these 11 patients had malignant lesions of the lung (three metastatic colorectal cancers and one primary lung cancer). There was no difference in median total hospital stay (8.5 days [range 7 to 13 days] vs. 8.0 days [range 3 to 49 days]), number of perioperative deaths (0 vs. 2 deaths), or long-term outcome between those patients with a positive chest CT undergoing thoracotomy/VATS and those patients with a negative chest CT. Overall, chest CT provided a positive yield of 4% and a positive predictive value of 36% for the detection of malignant lesions of the lung. Conclusions: Chest CT only minimally improved detection of malignant lesions of the lung over chest x-ray. Thoracotomy/VATS and wedge resection of lung nodules did not adversely affect outcome. The low positive yield and low positive predictive value of chest CT in the setting of a negative chest x-ray places in question the usefulness of routinely performing chest CT as part of the extent-of-disease work-up before hepatic resection.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Surgical and radiologic anatomy 20 (1998), S. 215-220 
    ISSN: 1279-8517
    Keywords: Temporal bone ; Retrotympanum ; Radio-anatomy ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Le but de ce travail était de définir avec précision en tomodensitométrie haute résolution l'imagerie du rétrotympanum. A partir de 66 TDMs des rochers réalisés chez 49 patients suivis en ORL, plusieurs structures du rétrotympanum ont été étudiées : éminence pyramidale, ponticulus, subiculum, crête cordale, sinus tympanique de proctor, sinus tympani et récessus du facial. Les variations morphologiques et de profondeur ont été notées ainsi que le rapport entre la pyramide et le canal facial. Dans un deuxième temps, à partir de 24 temporaux prélevés sur cadavres embaumés, explorés selon la même technique radiologique, les mêmes structures anatomiques ont été étudiées. Des corrélations anatomiques pour 6 temporaux ont été réalisées pour confirmer l'ensemble de nos hypothèse radiologiques. En tomodensitométrie la visibilité de l'éminence pyramidale était obtenue dans 100% des cas, celle de la crête cordale dans 52% des cas, du ponticulus dans 63% des cas et du subiculum dans 57% des cas. Pour ce qui est des différents récessus, le sinus tympani était visible dans 95% des cas, le sinus tympani de Proctor dans 38% des cas, la fossette de Grivot dans 47% des cas et le recessus du facial dans 80% des cas. La profondeur moyenne du sinus tympani était de 2.7 mm, le sinus tympani de Proctor mesurait 1.65 mm, la fossette de Grivot était évaluée à 2.1 mm et le récessus du facial à 2.2 mm. La meilleure connaissance de ces sinus et de leur variation aidera le chirurgien en particulier pour une tympanotomie postérieure ou un abord rétro-facial.
    Notes: Summary The aim of this study was to define the imaging of the retrotympanum precisely by means of high-resolution CT. Based on 66 scans of petrous bones performed in 49 patients observed in an otologic department, several retrotympanic structures were studied: the pyramidal eminence, ponticulus, subiculum, chordal ridge, tympanic sinus of Proctor, sinus tympani and recess of the facial n. The variations in morphology and depth were noted as well as the relationship between the pyramid and the facial canal. In a second phase the same anatomic structures were studied in 24 temporal bones removed from embalmed cadavers and investigated with the same radiologic technique. Anatomic correlations were made for six temporal bones to confirm the general applicability of our radiologic hypotheses. In CT the pyramidal eminence was visualised in 100% of cases, the chordal ridge in 52%, the ponticulus in 63% and the subiculum in 57%. As regards the different recesses, the sinus tympani was visualised in 95% of cases, the posterior tympanic sinus of Proctor in 38%, the fossula of Grivot in 47% and the facial recess in 80%. The mean depth of the sinus tympani was 2.7 mm and that of the tympanic sinus of Proctor was 1.65 mm; the fossula of Grivot was assessed as 2.1 mm and the facial recess as 2.2 mm. A better knowledge of these sinuses and their variations will aid the surgeon, particularly in a posterior tympanotomy or a retro-facial approach.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1279-8517
    Keywords: Shoulder ; Supraspinatus outlet syndrome ; Computed tomography ; Mineralization ; Subacromial space
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A reduction of the subacromial space and an increased subacromial pressure have been considered to play an important role in the pathogenesis of rotator cuff lesions. The objective of the current study was to develop a CT based method for measuring the acromiohumeral distance and inferior acromial mineralization. In seven patients with unilateral rupture of the rotator cuff and two with impingement syndrome, transverse CT images were obtained at a section thickness of 1 mm with muscular relaxation in a standardized position. The bones were then reconstructed three-dimensionally, and the minimal vertical distance between the acromion and the humerus was determined in three secondary frontal images on both sides. The distribution of mineralization within the inferior surface of the acromion was assessed using CT osteoabsorptiometry. Although the Constant score was significantly reduced in the diseased shoulders, the width of the subacromial space was not routinely lower than on the contralateral side. In seven cases the maximal inferior acromial mineralization was identical in both shoulders, and in two cases it was lower on the affected side. These preliminary data suggest that with muscular relaxation no narrowing of the subacromial space can be detected in secondary frontal CT images, and that a potential increase of subacromial pressure is not high enough to cause a measurable increase in inferior acromial bone density. The method presented makes it possible to investigate the pathogenesis of the supraspinatus outlet syndrome in vivo with greater precision than has so far been possible with conventional radiography.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1279-8517
    Keywords: Bone maturation ; Carpal bone ; Volume ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of our study was to measure the volume of each carpal bone during childhood and adolescence by image processing from computed tomography (CT) scans, and to analyze the relationship between the eight carpal bones. Thirteen CT scans were performed in nine normal prepubertal, peripubertal and post-pubertal children, six boys and three girls, aged 5-14 years. Each scan was processed in order to extract the carpal bones. The volume was computed for each bone. There was a significant correlation between carpal bone volume and age (0.55 〈 r 〈 0.79), and a very strong correlation between the volume of a given carpal bone and the volume of all the others, whatever the age (0.87 〈 r 〈 0.99, p 〈 0.01). Image processing is a potentially useful method for assessing bone maturation. The constant ratio between carpal bone volumes indicates that these bones interact with each other in wrist bone maturation
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Surgical and radiologic anatomy 20 (1998), S. 215-220 
    ISSN: 1279-8517
    Keywords: Temporal bone ; Retrotympanum ; Radio-anatomy ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Summary: The aim of this study was to define the imaging of the retrotympanum precisely by means of high-resolution CT. Based on 66 scans of petrous bones performed in 49 patients observed in an otologic department, several retrotympanic structures were studied: the pyramidal eminence, ponticulus, subiculum, chordal ridge, tympanic sinus of Proctor, sinus tympani and recess of the facial n. The variations in morphology and depth were noted as well as the relationship between the pyramid and the facial canal. In a second phase the same anatomic structures were studied in 24 temporal bones removed from embalmed cadavers and investigated with the same radiologic technique. Anatomic correlations were made for six temporal bones to confirm the general applicability of our radiologic hypotheses. In CT the pyramidal eminence was visualised in 100% of cases, the chordal ridge in 52%, the ponticulus in 63% and the subiculum in 57%. As regards the different recesses, the sinus tympani was visualised in 95% of cases, the posterior tympanic sinus of Proctor in 38%, the fossula of Grivot in 47% and the facial recess in 80%. The mean depth of the sinus tympani was 2.7 mm and that of the tympanic sinus of Proctor was 1.65 mm; the fossula of Grivot was assessed as 2.1 mm and the facial recess as 2.2 mm. A better knowledge of these sinuses and their variations will aid the surgeon, particularly in a posterior tympanotomy or a retro-facial approach.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Neurosurgical review 21 (1998), S. 52-57 
    ISSN: 1437-2320
    Keywords: Computed tomography ; extradural hematoma ; posterior fossa ; skull fracture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fourteen cases of an extradural hematoma of the posterior fossa (EDHPF), are presented and the clinical and radiological findings are described. The onset of symptoms was acute in 10 patients and subacute in the other 4. Hematomas occurred in the younger age groups with a clear male predominance. Nine cases had suffered a blow to the head. A fracture of the occipital bone was seen in 86% of the patients. The bleeder could be identified in 10 cases, and in 6 of these the source was a bleeding transverse sinus. The overall mortality was 14.2%, but only patients with an acute course died (20%). All subacute cases survived. This study revealed that the most important factors influencing mortality were late diagnosis and late treatment. Coexisting intracranial lesions had no influence on mortality. According to the literature, there has been a certain decrease in mortality in the acute and subacute course patients since the introduction of computed tomography (CT) scanning. Emphasis is placed on the importance of occipital soft-tissue swelling and occipital fracture as clues to the possible presence of extradural hematomas, and of using the CT in all such patients even if no clinical symptoms are present.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Panikstörung ; Computertomographie ; Neuroradiologie ; Hirnmorphologie ; Ätiologie ; Key words Panic disorder ; Computed tomography ; Neuroradiology ; Brain morphology ; Etiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary This CT study was designed to assess brain morphology in panic disorder with and without agoraphobia. Twenty-one patients and 21 normal control subjects matched for age and sex were investigated. Frontal and parieto-occipital cortex, temporal cortex, lateral ventricles and 3rd ventricle were evaluated by qualitative assessment on a 3-point scale (normal, questionable, abnormal). Patients showed significant bilateral enlargement of cortical cerebrospinal fluid (CSF) spaces (p〈0.01). The rating „abnormal” was given to none (0%) of the normal controls, but to 7 (33.3%) of the patients. Explorative analysis showed that these abnormalities were predominantly located in prefrontal regions. No qualitative differences were seen in the temporal cortex, lateral ventricles or third ventricle. These findings support the hypothesis that alterations in brain morphology are involved in the etiology of panic disorder. The lack of a correlation between CSF enlargement and duration of illness suggests that frontal CSF enlargement is a neurobiological vulnerability marker in panic disorder.
    Notes: Zusammenfassung In der vorliegenden CT-Studie wurde untersucht, ob in der Ätiologie der Panikstörung neben diskutierten psychosozialen, genetischen und biochemischen Faktoren auch hirnmorphologische Komponenten von Bedeutung sind. Anhand einer 3stufigen Skala wurde qualitativ die Hirnstruktur von 21 Patienten mit Panikstörungen mit und ohne Agoraphobie nach DSM-IV sowie von einer alters- und geschlechtsgleichen neuropsychiatrisch unauffälligen Kontrollgruppe bewertet. Folgende Hirnstukturen wurden qualitativ auf einer 3-Punkte-Skala (normal, fraglich, pathologisch) bewertet: frontaler und parietookzipitaler Kortex, temporaler Kortex, Seitenventrikel und 3. Ventrikel. Die Patienten mit Panikstörungen zeigten eine signifikante beidseitige Erweiterung des kortikalen Liquorraumes (p〈0,01). Die Beurteilung „pathologisch” wurde bei keiner Kontrollperson, aber bei sieben (33,3%) Patienten vergeben. Diese hirnstrukturellen Auffälligkeiten waren fast ausschließlich im präfrontalen Kortex lokalisiert. Keine signifikanten Gruppenunterschiede fanden sich in Bezug auf den temporalen Kortex, die Seitenventrikel und den 3. Ventrikel. Die Studienergebnisse zeigen, daß in der Ätiologie der Panikstörung auch hirnstrukturelle Veränderungen von Bedeutung sind. Da die Ausprägung dieser hirnstrukturellen Veränderungen nicht abhängig ist von der Krankheitsdauer, wird die präfrontale Liquorraumerweiterung als hirnbiologischer Vulnerabilitätsmarker der Störung interpretiert.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Fibrinolyse ; Intrazerebrale Blutung ; CT ; Kontrastmittel ; Komplikation ; Key words Fibrinolysis ; Cerebral hemorrhage ; Computed tomography ; Contrast medium ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary
    Notes: Zusammenfassung
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1437-9813
    Keywords: Key words Accessory hepatic lobe ; Torsion ; Ultrasonography ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A case of acute epigastric pain resulting from torsion of an accessory hepatic lobe is reported. Sonographic, computerized tomographic, and magnetic resonance findings are illustrated and the surgical management is discussed.
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  • 11
    ISSN: 1279-8517
    Keywords: Aortic bifurcation ; Vena cava confluence ; Computed tomography ; Ageing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The object of this retrospective study was to determine the sites of abdominal aortic bifurcation and inferior vena cava confluence in relation to age and sex. The study group comprised 180 subjects (90 males and 90 females) divided into 9 groups by age (in decades). The positions of the aortic bifurcation and the inferior vena cava confluence were evaluated by CT, and linear regression models were fitted to the data. The positions of the aortic bifurcation and venous confluence showed a highly significant downward shift with increasing age (p=0.0001). The shift was more pronounced in women. The mean site of the aortic bifurcation for the whole group was at lower L4 (range, upper L3 to upper S1); in males, it was at upper L4 (range, upper L3 to upper L5), and in females at lower L4 (range, upper L3 to upper S1). The mean site of the venous confluence for the whole group was at disc L4-L5 (range, lower L3 to upper S1); in males, it was at disc L4-L5 (range, upper L4 to disc L5-S1), and in females at disc L4-L5 (range, lower L3 to upper S1). Thus, the aorta and the inferior vena cava can extend as low as the level of S1. These data are of relevance in laparoscopic procedures, especially in laparoscopic lumbar discectomy.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 1279-8517
    Keywords: Aortic bifurcation ; Vena cava confluence ; Computed tomography ; Ageing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Le but de cette étude rétrospective était de déterminer la topographie de la bifurcation de l'aorte abdominale et de la confluence cave caudale en fonction de l'âge et du sexe. Le groupe étudié comprenait 180 sujets (90 de sexe masculin et 90 de sexe féminin) divisés en 9 groupes d'âge (9 décennies). Les positions de la bifurcation aortique et de la confluence veineuse cave caudale ont été évaluées par tomodensitométrie, et des modèles de régression linéaire ont été appliqués aux données recueillies. Un déplacement caudal des positions de la bifurcation aortique et de la confluence cave caudale était hautement corrélé à l'âge (p=0.0001). Le déplacement était plus prononcé chez les femmes. La position moyenne de la bifurcation aortique pour le groupe entier était la partie caudale de L4 (extrémités : partie supérieure de L3, partie supérieure de S1) ; chez les sujets de sexe masculin, elle se situait à la partie supérieure de L4 (extrémités : partie supérieure de L3, partie supérieure de L5), et dans le sexe féminin à la partie caudale de L4 (extrémités : partie supérieure de L3, partie supérieure de S1). La situation moyenne de la confluence cave caudale pour le groupe entier était au niveau du disque L4–L5 (extrémités : partie caudale de L3, partie craniale de S1) ; dans le sexe masculin elle se situait en regard du disque L4–L5 (extrémités : partie craniale de L4, disque L5–S1) et dans le sexe féminin au niveau du disque L4–L5 (extrémités : partie caudale de L3, partie craniale de S1). Ainsi, l'aorte et la veine cave caudale peuvent s'étendre aussi bas qu'au niveau de S1. Ces données trouvent leur application dans les procédures laparoscopiques, en particulier dans la discectomie lombaire.
    Notes: Summary The object of this retrospective study was to determine the sites of abdominal aortic bifurcation and inferior vena cava confluence in relation to age and sex. The study group comprised 180 subjects (90 males and 90 females) divided into 9 groups by age (in decades). The positions of the aortic bifurcation and the inferior vena cava confluence were evaluated by CT, and linear regression models were fitted to the data. The positions of the aortic bifurcation and venous confluence showed a highly significant downward shift with increasing age (p=0.0001). The shift was more pronounced in women. The mean site of the aortic bifurcation for the whole group was at lower L4 (range, upper L3 to upper S1); in males, it was at upper L4 (range, upper L3 to upper L5), and in females at lower L4 (range, upper L3 to upper S1). The mean site of the venous confluence for the whole group was at disc L4–L5 (range, lower L3 to upper S1); in males, it was at disc L4–L5 (range, upper L4 to disc L5–S1), and in females at disc L4–L5 (range, lower L3 to upper S1). Thus, the aorta and the inferior vena cava can extend as low as the level of S1. These data are of relevance in laparoscopic procedures, especially in laparoscopic lumbar discectomy.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    European radiology 8 (1998), S. 66-68 
    ISSN: 1432-1084
    Keywords: Key words: Heart angiosarcoma ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. We report a case of primary heart angiosarcoma and its appearance on plain and post-contrast computed tomography and magnetic resonance imaging in 21-year-old woman. The tumour involved the right atrium, expanded superiorly among the superior vena cava, ascending aorta and innominate vein, and infiltrated the pericardium. The tumour was disseminated into lungs, liver and bones at the time of its clinical presentation.
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  • 14
    ISSN: 1432-1084
    Keywords: Key words: Perineurioma ; Nerve sheath tumor ; Computed tomography ; Ultrasound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Perineurioma is an extremely rare benign tumor of the peripheral nervous system composed exclusively of perineurial cells. Imaging findings of this tumor are non-specific and the diagnosis is based on histologic studies. We report a case of perineurioma of the kidney in a 7-year-old girl discovered incidentally during the evaluation of a urinary tract infection. This is the first case of renal perineurioma reported in a child. We present the ultrasound and computed tomography findings of this histologically confirmed neoplasm.
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  • 15
    ISSN: 1432-1920
    Keywords: Key words Internal carotid artery ; Stapedial artery ; Computed tomography ; Magnetic resonance angiography ; Middle ear
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An 8-year-old child was examined because of conductive hearing loss with a retrotympanic mass on otoscopy. CT and MR angiography showed a large inferior tympanic artery traversing the hypotympanum and joining a thin, irregular internal carotid artery with a normal middle meningeal artery. These investigations, coupled with knowledge of the embryological development allowed a diagnosis of a complex vascular anomaly in the middle ear and avoided potential surgical complications.
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 40 (1998), S. 238-241 
    ISSN: 1432-1920
    Keywords: Key words Leiomyoma ; brain ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We present a case of intracranial parenchymal leiomyoma in a 20-year-old woman with a chief complaint of numbness and a painful sensation over the right limbs for several years. CT and MRI revealed an intensely enhancing calcified mass. The patient was well, without recurrence, 2 years after surgery.
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  • 17
    ISSN: 1432-1920
    Keywords: Key words Surgery ; trans-sphenoidal ; Cerebrospinal fluid fistula ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cerebrospinal fluid (CSF) leakage after trans-sphenoidal surgery is a troublesome complication with a risk of meningitis and pneumocephalus. We suggest CT-guided intrasphenoidal injection of fibrin sealant through a 12-gauge needle as a simple alternative to surgical management of CSF fistulae. We treated eight patients, operated via the trans-sphenoidal route (five pituitary adenomas, three craniopharyngiomas), for a postoperative CSF leak by CT-guided intrasphenoidal injection of fibrin sealant alone in three cases and fibrin sealant and autologous blood in 5. CT was obtained 10 days after the procedure in all cases. In four patients, the CSF leak was closed successfully at the first attempt. The procedure was repeated on the four remaining patients because only a reduction in leakage was obtained at the first attempt. This procedure preserves olfaction and avoids the risk of frontal lobe damage. It could therefore represent the treatment of choice in many cases of anterior cranial fossa postsurgical CSF leaks.
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  • 18
    ISSN: 1432-1920
    Keywords: Key words Brain ; Calcification ; perivenous ; Lupus erythematosus ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We present a case of neuropsychiatric lupus erythematosus with granular calcification in the basal ganglia and cerebral white matter on CT. Histopathologically, these were identified as perivenous necrotising lesions, with loss of axons and myelin sheaths and prominent dystrophic calcification.
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  • 19
    ISSN: 1432-1920
    Keywords: Key words Inner ear ; Aqueduct ; vestibular ; Endolymphatic duct ; Hearing loss ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied ten inner ears of five patients with a bilateral large vestibular aqueduct syndrome, using CT and MRI. Although the large vestibular aqueduct varied in size, a markedly dilated endolymphatic sac extending to the sigmoid sinus was demonstrated bilaterally on MRI in all patients. The cause of hearing loss in this syndrome is unclear. However, it is suggested that reflux of the protein-rich, hyperosmolar endolymph from the enlarged endolymphatic sac (EES) into the cochlea through a widely patent endolymphatic duct may damage the neuroepithelium. CT density and spin-echo MRI signal intensity of the endolymph in EES were markedly higher than those of CSF in eight inner ears of four patients. Increased density and high signal may indicate protein-rich, hyperosmolar endolymph. In some patients with sensorineural hearing loss and EES, the vestibular aqueduct may not appear dilated on CT. MRI is therefore necessary for correct diagnosis of this syndrome, which should more correctly be termed “large endolymphatic duct and sac syndrome”. Prominent EES may predict poor prognosis in this syndrome.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 40 (1998), S. 401-403 
    ISSN: 1432-1920
    Keywords: Key words Amyloidosis ; larynx ; Laryngocele ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A case of laryngeal amyloidosis associated with a laryngocele is reported. Preoperative CT showed diffuse thickening of the epiglottis, aryepiglottic folds and false vocal cords with well-defined calcific foci. MRI revealed contrast enhancement and increased signal intensity on T2-weighted images.
    Type of Medium: Electronic Resource
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  • 21
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 40 (1998), S. 462-465 
    ISSN: 1432-1920
    Keywords: Key words Temporal bone ; abnormalities ; CHARGE association ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We reviewed the CT examinations of the temporal bone, performed with 1-mm-thick contiguous sections, of seven patients with the CHARGE association. We found abnormalities of the incus and stapes, with ossicular chain fixation, absence of the stapedius muscle and oval window, hypoplasia or dysplasia of the vestibule and absence of the semicircular canals in all ears. The pyramidal eminence and tympanic sinus were absent and there were anomalies of the cochlea in 13 of 14 ears. Absence of the semicircular canals is the most specific change in patients with the CHARGE association.
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  • 22
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 40 (1998), S. 335-337 
    ISSN: 1432-1920
    Keywords: Key words Thyroid ; lingual ; Goitre ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We present the CT and MRI findings in a 75-year-old woman with a huge pathologically proven lingual thyroid which underwent goitrous degeneration. CT and MRI showed a midline, tongue-based, exophytic mass with areas of necrosis and heterogeneous contrast enhancement, as seen in large goitres in the normal thyroid gland.
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  • 23
    ISSN: 1432-1920
    Keywords: Key words Glioblastoma ; necrosis ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In a previous study, we found that the extent of necrosis was the only radiological feature which correlated significantly with survival in patients with glioblastoma. The aim of this paper was to evaluate the variability and prognostic value of the extent of the necrotic area as seen on contrast-enhanced MRI and CT in a larger series. We studied 72 patients who underwent surgical removal of supratentorial glioblastomas and had CT and/or MRI with contrast medium before surgery; 38, all undergoing the same treatment (surgery plus radiotherapy), were followed clinically. Necrosis within the tumour varied greatly, ranging from none (only 1 case) to involvement of 76 % of the tumour. Survival data in the subgroup suggested that only patients with a small area of necrosis (less than 35 % of the tumour) had a significantly longer survival time. When necrosis involved more than 35 % of the mass, patients had a shorter survival time, without any further correlation with the extent of necrosis.
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  • 24
    ISSN: 1432-1920
    Keywords: Key words Arachnoid granulations ; Computed tomography ; Magnetic resonance imaging ; Magnetic resonance venography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report MRI and angiographic findings of an unusual giant arachnoid granulation in the left sigmoid sinus in a boy with headache. Its signal intensity was lower than that of cerebral cortex on T1-weighted images and higher on T2 weighting, mimicking dural sinus thrombosis.
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  • 25
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    Neuroradiology 40 (1998), S. 261-263 
    ISSN: 1432-1920
    Keywords: Key words Head and neck ; neoplasms ; Sarcoma ; synovial ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We present the CT and MRI findings of a histologically proven synovial sarcoma arising in the left parapharyngeal space of a 21-year-old man. CT was useful for confirming the presence of calcification within the tumour, which may be a favourable prognostic sign, and in excluding involvement of cortical bone. The CT and MRI findings were, however, nonspecific. MRI was superior to CT for assessing the topographical relationships of the tumour to the vessels and the invasion of neighbouring structures.
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  • 26
    ISSN: 1432-1920
    Keywords: Key words Cardiopulmonary resuscitation ; Intracranial gas ; Computed tomography ; postmortem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report four patients in whom gas was seen in the head on CT shortly after cardiopulmonary resuscitation. The gas was in the posterior cranial fossa, presumably within veins, or in the cavernous sinus. The cause of the cardiac arrest was myocardial infarction in three patients and hanging in one. All had peripheral or central venous lines. The mechanism by which gas appeared in the intracranial veins is discussed.
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  • 27
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    Neuroradiology 40 (1998), S. 332-334 
    ISSN: 1432-1920
    Keywords: Key words Microcephalia vera ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract CT and MRI findings in three patients, two of them siblings, with microcephalia vera are presented. In this rare entity, a very small brain with an extremely thin, smooth cortex and increased surrounding cerebrospinal fluid are observed.
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  • 28
    ISSN: 1432-1920
    Keywords: Key words Anticoagulants ; Cerebral hemorrhage ; Autopsy ; Computed tomography ; Hematoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report the first case in which a fluid-blood interface was identified at autopsy in a patient with acute intracerebral hematoma on anticoagulant therapy. Anticoagulation may be one of the major factors contributing to the production of an intracerebral blood sedimentation level.
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  • 29
    ISSN: 1432-1920
    Keywords: Key words Hydatid cysts ; growth ; Echinococcus granulosus ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report the case of a 25-year-old man with multiple bilateral hydatid cysts of the brain in whom we were able to assess the growth rate of the cysts on repeated examination. On average, the cysts increased in diameter by 1 cm per month.
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  • 30
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    Neuroradiology 40 (1998), S. 6-10 
    ISSN: 1432-1920
    Keywords: Key words Subarachnoid haemorrhage ; Angiography ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study was designed to assess the necessity for a second angiogram study in patients in whom initial angiography after primary subarachnoid haemorrhage (SAH) was negative. During a 12-year period, 122 of 694 patients (17.5 %) had negative initial angiograms. CT, available for 98 patients, showed a preponderance of subarachnoid blood in the perimesencephalic cisterns in 50 of 73 patients (68.5 %) in whom blood was visible on CT. Angiography, repeated in 67 patients, revealed an aneurysm in 4 (6 %): 2 had an aneurysm of the anterior communicating artery, 1 of the posterior inferior cerebellar artery, and 1 of the P2 segment of the posterior cerebral artery. CT showed subarachnoid blood in the interpeduncular and ambient cisterns in this last case, and a preponderance of subarachnoid blood outside the perimesencephalic cisterns in the remaining 3 patients.
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  • 31
    ISSN: 1432-1920
    Keywords: Key words Echinococcosis ; brain ; Hydatid disease ; brain ; Albendazole ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a case of cerebral hydatid disease demonstrated by CT and MRI, treated with albendazole. Follow-up showed complete dissapearance of the cysts with residual focal calcification on CT and presumed gliosis on MRI.
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  • 32
    ISSN: 1432-1920
    Keywords: Key words Secretory meningioma ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Secretory meningioma is a rare entity which may be characterised by imaging features unusual for other subtypes of meningoma, such as low attenuation on CT, high (fat-tissue equivalent) signal intensity on T1-weighted MRI, marked surrounding oedema, and irregular contrast enhancement. We report a case of secretory meningioma and review the literature.
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  • 33
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    Neuroradiology 40 (1998), S. 752-754 
    ISSN: 1432-1920
    Keywords: Key words Nasal cavity ; Fibrous dysplasia ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fibro-osseous lesions of the sinonasal region are relatively frequent, but those strictly confined to the nasal cavity are rare. We report an atypical fibro-osseous lesion in the nasal cavity and describe its radiological features. The differential diagnosis is discussed.
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  • 34
    ISSN: 1432-1920
    Keywords: Key words Schwannoma Malignant ; Leptomeningeal metastasis ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A malignant retroperitoneal schwannoma in a patient without von Recklinghausen's disease is reported. Ossification in the tumour, shown on CT and MRI in this previously untreated patient is exceptional. MRI demonstration of spinal leptomeningeal metastases supports the hypothesis of haematogenous metastatic spread of systemic malignant tumours to the leptomeningeal spaces.
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  • 35
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    Neuroradiology 40 (1998), S. 651-655 
    ISSN: 1432-1920
    Keywords: Key words Pituitary adenoma ; Suprasellar tumour ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We present five proven giant pituitary adenomas studied by CT and MRI, and review the clinical and imaging findings. Our aim was to examine the radiologic appearances and to search for criteria useful in distinguishing these tumors from other sellar and suprasellar tumours, mainly craniopharyngioma. The main differences from small adenomas were high prevalence of macrocysts, a more invasive behaviour and a clinical picture dominated by mass effect rather than endocrine disturbance. Factors supporting the diagnosis of pituitary adenoma in a giant intra- and suprasellar mass include: infrasellar extension, absence of calcification and presence of low-signal cysts on T1-weighted images.
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  • 36
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    Neuroradiology 40 (1998), S. 662-663 
    ISSN: 1432-1920
    Keywords: Key words Marble brain syndrome ; Osteopetrosis ; Renal acidosis ; Calcification intracranial ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cerebral calcification in children is frequently associated with systemic metabolic disease. We present a case of “marble brain syntrome”, which showed this abnormality.
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  • 37
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    Neuroradiology 40 (1998), S. 577-579 
    ISSN: 1432-1920
    Keywords: Key words Fibroma ; chondromyxoid ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Only a smal proportion of cases of this rare neoplasm occur in the skull. We present an unusually extensive tumour in a young man.
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  • 38
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    Pediatric nephrology 12 (1998), S. 420-429 
    ISSN: 1432-198X
    Keywords: Key words: Osteoporosis ; Bone density ; Growth ; Renal insufficiency ; Ultrasound ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The monitoring of bone metabolism and skeletal development during childhood and adolescence is becoming increasingly important in the prevention of osteoporosis. This is especially important in patients with chronic disorders. The predominant changes in the skeletal system during growth occur as geometric adaptation processes which lead to an increase in bone mass and bone strength. These changes can be measured with linear absorption methods (single-photon absorptiometry, dual-photon absorptiometry, dual-energy X-ray absorptiometry), computed tomographic procedures (peripheral quantitative computed tomography, quantitative computed tomography), and sonographic procedures. The aim of this review is to explain the problems of interpretation of the investigations due to growth-dependent changes. Almost all methods and their parameters, such as bone density, spongiosa density, cortical density, ultrasound transmission velocity, etc., are influenced, in varying degree, by growth-dependent skeletal changes.
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  • 39
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Samenblasenzysten ; Nierenagenesie ; Langzeitverlauf ; Computertomographie ; Magnetresonanztomographie ; Key words Seminal vesicle cysts ; Renal agenesis ; Long-term results ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Congenital seminal vesicle cysts associated with ipsilateral renal agenesis or dysplasia are rare malformations. Even though they are more often diagnosed today due to the introduction of advanced, sectional imaging techniques as CT and MRI, no reliable data about the prevalence of this malformation are available. This study reports seven consecutive cases, with long-term follow-up in five cases (26–119 months, mean 52 months). All patients underwent sonography, excretory urography, CT and MRI. Only two of seven patients presented nonspecific symptoms of the lower urinary tract; five were asymptomatic. In all cases sonography revealed the cystic character of the retrovesical enlargement. The anatomy of the lower pelvis was most accurately shown on MRI, which depicted the ectopic insertion of the ureter into the seminal vesicle in five cases. Cysts demonstrated high signal intensities in T1- and T2-weighted spin-echo images. In five cases the CT density was over 40 HU. Whereas one patient (15 years) presented significant enlargement of the cysts 10 years after primary diagnosis with compression of the urinary bladder, four patients showed no changes of their malformation in the follow-up examinations. The present data therefore support the concept of treating only symptomatic patients.
    Notes: Zusammenfassung Kongenitale Samenblasenzysten mit ipsilateraler Nierenagenesie oder -dyplasie sind seltene angeborene Mißbildungen. Seit Einführung moderner Schnittbildverfahren werden sie jedoch zunehmend häufiger diagnostiziert. Dennoch fehlen bislang genaue Angaben über die Prävalenz dieses Mißbildungsmusters. Diese Studie berichtet über 7 konsekutive Fälle und dokumentiert in 5 Fällen Langzeitbeobachtungen (26–119 Monate, Mittel 52 Monate). Von allen Patienten liegen Ultraschalluntersuchungen, Ausscheidungsurographien sowie Computer- und Kernspintomographien vor. Nur 2 von 7 Patienten wiesen unspezifische Symptome des unteren Harntraktes auf, alle anderen waren asymptomatisch. Von allen bildgebenden Verfahren zeigte die Kernspintomographie am genausten die Veränderungen im kleinen Becken und ihre Beziehungen zum Urogenitalsystem. Die Zysten wiesen eine hohe Signalintensität in T1- und T2-gewichteten Spin-Echo-Sequenzen auf. Computertomographisch fanden sich in 5 Fällen Dichtewerte über 40 HE. Während ein Patient (15 Jahre alt) 10 Jahre nach Erstdiagnose eine erhebliche Vergrößerung der Zysten mit Verdrängung der Harnblase aufwies, zeigten 4 Patienten bei der Nachuntersuchung keine Veränderung der Fehlbildung. Die vorliegenden Daten stützen somit das Konzept, nur symptomatische Patienten zu therapieren.
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  • 40
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    Der Radiologe 38 (1998), S. 954-957 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Epidurales Hämatom ; Orbita ; Trauma ; Hämatom ; Computertomographie ; Key words Extradural hematoma ; Orbit ; Trauma ; Hematoma ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Subperiostal hematomas (SPOH) of the orbit are mostly of traumatic origin, but may occur spontaneously. In patients with frontal and temporal extradural hematomas, concomitant SPOH of the ipsilateral orbit have sporadically been observed. We report clinical and radiological findings of a patient and a review of the literature and discuss the development of SPOH.
    Notes: Zusammenfassung Subperiostale Hämatome der Orbita (SPOH) treten überwiegend posttraumatisch, selten auch spontan auf. Gelegentlich wurde bei Patienten mit einem frontalen oder temporalen Epiduralhämatom ein SPOH der ipsilateralen Orbita beobachtet. Wir stellen anhand einer eigenen Patientin und einer Literaturübersicht die klinischen und radiologischen Befunde vor und diskutieren die Entstehung.
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  • 41
    ISSN: 1432-1084
    Keywords: Key words: Clavicle ; Medial clavicular epiphysis ; Computed tomography ; Bone age determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The development of the medial clavicular epiphysis and its fusion with the clavicular shaft have been a subject of medical research since the second decade of this century. Computed tomography provides the imaging modality of choice in analyzing the maturation process of the sternal end of the clavicle. In a retrospective study, we analyzed normal development in 380 individuals under the age of 30 years. The appearance of an epiphyseal ossification center occurred between ages 11 and 22 years. Partial union was found from age 16 until age 26 years. Complete union was first noted at age 22 years and in 100 % of the sample at age 27 years. Based on these data, age-related standardized age distributions and 95 % reference intervals were calculated. Compared to the experience recorded in the relevant literature, there are several landmarks that show no significant change between different ethnic groups and different periods of publication; these are the onset of ossification, the time span of partial union, and the appearance of complete union. Despite the relatively long time spans of the maturation stages, bone age estimation based on the study of the development of the medial clavicular epiphysis may be a useful tool in forensic age identification in living individuals, especially if the age of the subject is about the end of the second or the beginning of the third decade of life (e. g. in determining the applicability of adult or juvenile penal systems). Another possible use is in identifying human remains whose age is estimated at under 30 years.
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  • 42
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    European radiology 8 (1998), S. 100-102 
    ISSN: 1432-1084
    Keywords: Key words: Teratoma ; Posterior mediastinum ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The vast majority of germ cell tumors in the thorax arise at or near the thymus. We report a case of a 41-year-old man with mature teratoma of the posterior mediastinum. He was asymptomatic and was incidentally found to have a posterior mediastinal mass. Computed tomography was helpful in suggesting a diagnosis of mature teratoma by demonstrating the presence of fat and calcification. The differential diagnosis included neurogenic tumors, liposarcoma, and extramedullary hematopoiesis.
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  • 43
    ISSN: 1432-1084
    Keywords: Key words: Knee ; Femoral trochlea ; Ultrasonography ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The aim of the study was to verify the efficacy of ultrasonography (US) in evaluating the morphology of normal trochlea, especially the sulcus angle and the trochlear depth, in comparison with computed tomography (CT) (gold standard). The knees of 11 asymptomatic volunteers were subjected to US and CT evaluation of the same section planes and the results were compared. For statistical evaluation Spearman's correlation coefficient analysis was used. A statistically significant correlation was found between the two diagnostic procedures (sulcus angle: r = 0.820; trochlear depth: r = 0.802; Spearman's correlation coefficient) and the intra-observer variability for the US measurements (sulcus angle: r = 0.966; trochlear depth: r = 0.914; Spearman's correlation coefficient). The mean value of sulcus angle and trochlear depth was 132 ° and 5.6 mm, respectively, similar to those reported in the literature. We conclude that evaluation by US of both sulcus angle and trochlear depth is as reproducible and sensitive as that performed with CT.
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  • 44
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    European radiology 8 (1998), S. 1099-1105 
    ISSN: 1432-1084
    Keywords: Key words: Aorta ; Pulmonary arteries ; Computed tomography ; Magnetic resonance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Several excellent imaging modalities are available for studying the great vessels of the chest noninvasively. Besides computed tomography (CT), magnetic resonance imaging (MRI) and echocardiography (in particular the transesophageal approach) can accurately depict abnormalities of the thoracic vasculature, and are a valuable substitute for contrast angiography in most circumstances. The aim of this paper is to provide a comprehensive review of the current contribution of CT and MRI to the diagnosis of great vessel pathology of the chest.
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  • 45
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    European radiology 8 (1998), S. 97-99 
    ISSN: 1432-1084
    Keywords: Key words: Gated MRI ; Computed tomography ; Heart ; Left atrium ; Neoplasms ; Leiomyosarcomas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Cardiac leiomyosarcoma is a rare tumour which can grow either intramurally or extramurally. Its prognosis is dismal. Surgery lengthens survival, but recurrences usually occur in the short term. Gated MRI is useful for the assessment of cardiac masses since it provides fine spatial and contrast resolution. We present the case of a left atrial leiomyosarcoma whose recurrence was diagnosed by gated MRI. Our patient underwent a second resection but died soon after.
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  • 46
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    European radiology 8 (1998), S. 471-473 
    ISSN: 1432-1084
    Keywords: Key words: Lymphangioleiomyomatosis ; Retroperitoneum ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Lymphangioleiomyomatosis is a rare disease involving the lung, lymphatic trunk and lymph nodes. Sometimes it appears in the retroperitoneum with or without subsequent development in the lungs. We present a 52-year-old woman with retroperitoneal location of the disease. We discuss the abdominal CT appearance, the cytologic and immunophenotypic features and a preoperative differential diagnosis is attempted.
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  • 47
    ISSN: 1432-1084
    Keywords: Key words: Stroke ; Venous occlusions ; Computed tomography ; MRI ; Diffusion ; Echoplanar imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. In this paper, the authors present the contribution of CT and MRI to the diagnosis of acute stroke caused by arterial or venous occlusion. The term “early” used in this context means within 6 h of the onset of symptoms. Signs of early ischemic edema are subtle and sometimes difficult to detect by CT or MRI. The purpose of this presentation is to familiarize the clinician and the radiologist with the subtle brain parenchymal changes seen within the first 6 h after onset of symptoms, in order to improve detection of early ischemic infarction and to improve patient care.
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  • 48
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    European radiology 8 (1998), S. 1425-1428 
    ISSN: 1432-1084
    Keywords: Key words: Choriocarcinoma ; Stomach ; Pancreas ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. In this report we present the CT findings of two non-gestational,extragonadal choriocarcinomas, one arising within the stomach and one in the pancreas. These are rare tumours and a pancreatic primary site has not been previously described.
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  • 49
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    European spine journal 7 (1998), S. 344-347 
    ISSN: 1432-0932
    Keywords: Key words Lipoma ; Computed tomography ; Magnetic resonance imaging ; Radiography ; Vertebral
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Osseous lipomata of vertebral bodies are rare. We present a very unusual case where adjacent vertebrae are involved and the plain radiographic and scintigraphic appearances gave cause for some concern. The findings on plain films, scintigraphy, computed tomography and magnetic resonance imaging are discussed.
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  • 50
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    Skeletal radiology 27 (1998), S. 161-163 
    ISSN: 1432-2161
    Keywords: Key words Parosteal osteoma ; Iliac bone ; Computed tomography ; Magnetic resonance imaging ; Partial regression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A 33-year-old patient with a 2-year history of intermittent pain in the right gluteal region and thigh presented with a large sclerotic lesion of the iliac bone. From the findings on radiography, scintigraphy, CT and MRI, a giant parosteal osteoma was suspected. The histological examination confirmed the diagnosis. Since the lesion was extensive it was observed with periodic follow-up examinations. At present, 5 years after the diagnosis, the patient is asymptomatic and imaging studies show that the lesion persists with reduction of sclerosis and size. The tumor was on the surface as well as intramedullary – only one other case with such a distribution is known to us – and it was also in the iliac bone.
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  • 51
    ISSN: 1433-0350
    Keywords: Key words Posterior cranial fossa surgery ; Tumours ; Childhood ; Computed tomography ; Duraplasty ; Paediatric neurosurgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract At the Department of Neurosurgery, Hradec Králové, 454 children (aged under 18 years) were operated on for posterior cranial fossa lesions in a period of 49 years (1948–1996). The majority (402) had tumours: cerebellar astrocytomas 149 (37.1%), medulloblastomas 139 (34.6%), brain stem gliomas 46 (11.4%), ependymomas 28 (7.0%), and others 40 (9.9%). Postoperative mortality was compared for the pre-CT era (1948–1977) and the CT era (1978–1996): astrocytomas (8.6%:4.7%), medulloblastomas (14.9%:2.9%), brain stem gliomas (21.7%:19.0%), ependymomas (18.2%:6.3%), and others (40.0%:7.4%). The initially high mortality was due to insufficient intracranial decompression, brain oedema and disturbances of cerebrospinal fluid circulation. Obstructive hydrocephalus was treated in 53 children with tumours and 25 with aqueduct stenoses, by Torkildsen's drainage in 5.5%, and/or by catheterisation of aqueduct in 12.3%. The main postoperative complications of medial posterior fossa surgery in 429 children operated on were: pseudomeningocele (12.3%), active hydrocephalus (6.2%) and CSF leakage (4.6%). Only 8.2% had shunts placed for these complications. We presume that this low percentage of shunts used results from a frequent use of duraplasties and drains installed at the primary operation. The dura mater was initially (1948–1954) left open (50 cases), and later (1955–1958) also sutured (37 cases), and from 1958, onward, and especially from 1961, reconstructed by a medial approach by means of various grafts (377 cases). In all, duraplasty was performed in 81.6% of cases. The grafts used for dura mater reconstruction were prepared from autogeneic (1.6%), allogeneic (72.3%), xenogeneic (24.8%), or synthetic (1.3%) material. They were successful in 99.2% of cases (all materials). Our own suture technique for posterior fossa duraplasty is presented.
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  • 52
    ISSN: 1433-0350
    Keywords: Key words Diffuse astrocytoma ; Bilateral thalamic astrocytomas ; Computed tomography ; Magnetic resonance imaging ; Hyperfractionated radiotherapy ; Chemotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report the case of a 13-year-old girl with diffuse bilateral thalamic astrocytomas. Incoordination was observed at the onset. Cranial computed tomography (CT) showed enlarged thalami, and magnetic resonance imaging (MRI) revealed these lesions to be symmetrically enlarged with high intensity on the T2-weighted image. Owing to these atypical findings in the neuroimaging studies, we had difficulty in making the correct diagnosis of a brain tumor. After the diagnosis of diffuse bilateral thalamic astrocytomas was obtained, we performed hyperfractionated radiotherapy followed by chemotherapy. Radiation therapy was effective for a while, but the girl's condition deteriorated again and she died 8 months after admission. Although diffuse bilateral thalamic astrocytomas are difficult to diagnose because they do not resemble most other neoplasms on neuroimaging studies, pediatricians should keep this entity in mind in order to arrive at a precise and prompt diagnosis.
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  • 53
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Computertomographie ; Elektronenstrahlcomputertomographie ; Dosis ; Key words Computed tomography ; electron-beam ; Computed tomography ; dose ; Computed tomography ; helical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary To compare patient dose and image quality of electron-beam-CT vs. spiral-CT by means of phantom measurements. An EBCT scanner (C-150 XP) and a spiral-CT scanner (GE HiSpeed Advantage) were used to scan three different phantoms. Administered dose, high contrast (HC) resolution, low contrast (LC) lesion detectability and the width of the radiation beams were measured. EBCT showed 25–35% lower HC resolution in comparison to spiral-CT. LC lesion detectability showed equivalent results for S/N vs. patient dose using 3 mm collimation with EBCT and spiral-CT, whereas spiral-CT was superior for 1,5 and 6 mm collimation. Dose measurements revealed a 2 fold higher patient dose using EBCT with 1,5 mm or 6 mm collimation compared to spiral-CT using equivalent scan parameters. No differences were seen using 3 mm collimation. Differences were due to insufficient beamside collimation of the EBCT. The use of EBCT with 6 mm collimation should be avoided, because of impaired performance. Using 3 mm collimation, EBCT showed comparable performance like state of the art spiral-CT despite lower HC resolution.
    Notes: Zusammenfassung Die vorliegende Untersuchung nimmt einen Vergleich der applizierten Dosis und der resultierenden Bildqualität der Elektronenstrahl-CT (EBCT) im Volumenmodus und der Spiral-CT anhand von Phantommessungen vor. Mit EBCT (C-150 XP) und Spiral-CT (GE HiSpeed Advantage) wurden Messungen zur Niedrigkontrast- und Hochkontrastauflösung, Dosismessungen und Messungen der Röntgenstrahlbreite mit verschiedenen Phantomen durchgeführt. Die Hochkontrastauflösung liegt in der EBCT im Volumenmodus ca. 25–35% unter den Werten der Spiral-CT. Die Niedrigkontrastauflösung zeigt für 3 mm Kollimation bei EBCT und Spiral-CT ähnliche S/N Werte, bei 1,5 mm und insbesondere 6 mm Kollimation ist die Spiral-CT deutlich überlegen. Bei der EBCT mit 1,5-mm- und 6-mm-Kollimation ergibt sich eine doppelt so hohe Patientendosis wie bei der SCT, während bei 3-mm-Kollimation die Patientendosis gleich groß ist. Als Ursache hierfür wurde eine ungenügende strahlseitige Kollimation der EBCT gefunden. Die 6-mm-Kollimation am EBCT sollte wegen der schlechteren Niedrigkontrastauflösung und der höheren Dosis nicht verwendet werden. Bei einer Kollimation von 3 mm haben EBCT und Spiral-CT eine ähnliche Performance bei geringerer Hochkontrastauflösung der EBCT.
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  • 54
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    Der Radiologe 38 (1998), S. 637-644 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Notfalldiagnostik ; Polytrauma ; Schockraum ; Computertomographie ; Key words Emergency ; Multiple trauma ; Trauma emergency room ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The management of multiple trauma patients has improved recently. Surgeons’ education, preclinical rescue structures, initial clinical survey and therapeutic strategies, as well as diagnostic imaging, have progressed. Plain film imaging is increasingly being abandoned in favor of CT. Fast imaging techniques (spiral CT) have led to the inclusion of CT in the primary survey. To minimize the risk to the patient during prolonged diagnostic time, algorithms have to be defined concerning structures, emergency room equipment and quality. Basics, state of the art and suggestions concerning management of multiple trauma patients are presented and discussed from the radiologist’s point of view.
    Notes: Zusammenfassung Das Management schwerverletzter Patienten hat in den letzten Jahren viele Verbesserungen erfahren. Neben Ausbildungsspezialisierungen (Unfallchirurgie), präklinischen Strukturveränderungen (Notarzt- und Rettungswesen), frühklinischen Ablaufoptimierungen (Handlungsleitlinien) und Änderung klinischer Behandlungsstrategien (konservativ/operativ/interventionell) ist auch die initiale bildgebende Diagnostik bei polytraumatisierten Patienten im Wandel. Die bislang im Vordergrund stehende konventionelle Röntgendiagnostik tritt im Verhältnis zu der modernen Schnittbilddiagnostik (insbesondere CT) zunehmend in den Hintergrund. Vor allem seit Einführung der Spiral-CT-Technik ist auch in Deutschland die Tendenz zu ausgedehnter, primärer CT-Diagnostik zu verfolgen. Um Gefährdungen des kritischen Patientenguts zu minimieren müssen aber sowohl strukturelle, räumliche als auch qualitative Voraussetzungen als Standard definiert werden. Grundlagen, Stand der Dinge sowie Verbesserungsvorschläge zum Notfallmanagement polytraumatisierter Patienten aus radiologischer Sicht werden vorgestellt und diskutiert.
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  • 55
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    Der Radiologe 38 (1998), S. 693-701 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Abdominaltrauma ; Ultraschall ; Computertomographie ; Key words Abdominal trauma ; Ultrasonography ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In Europe ultrasonography has displaced diagnostic peritoneal lavage (DPL) in the primary survey of polytraumatized patients with suspected abdominal trauma. Hemodynamically unstable patients who are brought to the emergency room with blunt abdominal trauma will go directly to the operating room after a rapid ultrasonography examination with evidence of hemoperitoneum. In hemodynamically stable patients, in addition to ultrasonography, computed tomography can be done. This is especially efficient if evaluation with sonography is not completely possible or shows little pathology (e.g. small amounts of hemoperitoneum).
    Notes: Zusammenfassung Die Sonographie hat die diagnostische Peritoneallavage in Europa als primäres diagnostisches Verfahren beim Abdominaltrauma abgelöst. Wird beim kreislaufinstabilen Patienten im Schockraum bei der Sonographie freie Flüssigkeit nachgewiesen, ist die bildgebende Diagnostik beendet, der Patient wird laparotomiert. Bei hämodynamisch stabilen Patienten läßt sich neben der Sonographie auch die Computertomographie einsetzen. Dies ist in der Akutphase der Versorgung („erste Stunde”) besonders dann sinnvoll, wenn die Sonographie nicht sicher beurteilbar oder auffällig ist (z.B. geringe Mengen freier Flüssigkeit).
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  • 56
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    European archives of psychiatry and clinical neuroscience 248 (1998), S. 272-276 
    ISSN: 1433-8491
    Keywords: Key words Schizophrenia ; Epithalamus ; Habenula ; Pineal gland ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We evaluated the prevalence and the size of epithalamus calcifications (EC) and choroid plexus calcifications (CPC) on computed tomography (CT) scans in a group of 64 schizophrenic patients and in a group of 31 healthy controls. The associations between cerebral calcifications, demographic variables, and other brain morphological characteristics (particularly cerebral ventricular size and cortical atrophy) in both, patients and controls, were also considered. A significant increase in size of the epithalamic-region calcifications in schizophrenic patients was found, whereas there was no evidence of increase in both, dimension and prevalence, of choroid plexus calcification. Such dimensional increase was unrelated to the duration of illness and therefore did not seem to be iatrogenic or secondary to the disease. A correlation was found between epithalamus calcifications and cortical atrophy and third-ventricle enlargement, suggesting that calcifications of this cerebral region may be associated with lesions of third-periventricular areas and of circuitries hypothesized to be involved in the pathophysiology of schizophrenia.
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  • 57
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    Knee surgery, sports traumatology, arthroscopy 6 (1998), S. 173-180 
    ISSN: 1433-7347
    Keywords: Key words Patellofemoral joint ; Computed tomography ; Electromyography ; Quadriceps ; muscle ; Vastus medialis obliquus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Sports Science
    Notes: Abstract In this study, the effect of dynamic stabilizers on the patellofemoral (PF) joint was investigated in normal volunteers (group I) and in patients with patellar pain (group II) or instability (group III) by using computed tomography (CT) analysis and integrated electromyography (iEMG) of the quadriceps muscle. Nine subjects (16 knees) from group I, 10 patients (12 knees) from group II and 8 patients (12 knees) from group III were included in the study. CT scans of the PF joint with quadriceps contracted (QC) and uncontracted (QU) and iEMG of vastus medialis obliquus (VMO), vastus lateralis (VL) and rectus femoris (RF) were obtained with the aid of a specially designed jig at 0°, 15°, 30° and 45° of knee flexion. The same muscle contraction pattern simulating closed kinetic chain exercise was used for both CT and iEMG. The difference between the congruence angles (CA) and tilt angles (PTA) in QC and QU positions and VMO:VL ratio from the iEMG were calculated separately for each flexion angle. CA was increased in all groups with quadriceps contraction at 0° and 15° of flexion. PTA was decreased in group I and increased in groups II and III with quadriceps contraction at the same flexion angles. This difference was statistically significant in group III at 0° and 15° of flexion. Quadriceps contraction did not affect the patellar position significantly even in the instability group at 45° of flexion. In all flexion angles the balanced VMO:VL activity ratio was observed only in group I. In the other goups, VL activity was higher than VMO activity except at 45° of flexion. These findings do not support the hypothesis of dominant centralizing effect of VMO on the patella in extension, but the effect of the VMO may be more clearly demonstrated by measuring PTA in both QC and QU positions.
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  • 58
    ISSN: 1619-7089
    Keywords: Key words: Lymphoma staging ; Computed tomography ; Whole-body positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The purpose of this study was to evaluate whole-body positron emission tomography (WB-PET) as a staging modality in Hodgkin’s disease (HD) and non-Hodgkin lymphoma (NHL) and to compare it with computed tomography (CT) in a retrospective study. Seventy-one WB-PET studies using fluorodeoxyglucose (FDG) and 49 CT examinations were performed in 19 women and 31 men. Transaxial images were acquired and reformatted coronally and sagittally in PET. CT sections were obtained from the skull base to the pelvic floor. The written reports of the imaging data were compared with a reference standard constructed on the basis of all the data on the individual patients, including clinical follow-up of at least 6 months. The sensitivity and specificity of PET were, respectively, 86% and 96% for HD (n=53), and 89% and 100% for NHL (n=18). For CT sensitivity and specificity were 81% and 41% for HD (n=33) and 86% and 67% for NHL (n=16). Differences between PET and CT sensitivities were not significant, while in HD there was a significant difference in the specificity of PET and CT examinations, mainly because CT was unable to distinguish between active or recurrent disease and residual scar tissue after therapy. FDG tumour uptake was found in high- as well as low-grade NHL patients. In conclusion, PET appears to be highly sensitive and specific for staging of lymphoma. It is at least as sensitive as CT, and more specific, particularly in patients undergoing restaging, where a well-recognized diagnostic dilemma in CT is the presence of a post-therapeutic residual mass.
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  • 59
    ISSN: 1619-7089
    Keywords: Key words: Technetium-99m galactosyl human serum albumin ; Hepatic functional reserve ; Hepatic resectability ; Occlusion of the unilateral portal vein ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. It is extremely important to have a good grasp of the acceptable limit of hepatectomy before operation because postoperative liver failure can take a fatal course; however, baseline data on the limit of hepatectomy have not been clearly defined. We therefore evaluated and compared the predicted remnant liver function obtained by computed tomography(CT) and technetium-99m diethylenetriamine penta-acetic acid-galactosyl human serum albumin (99mTc-GSA) liver scintigraphy in order to obtain precise data regarding remnant liver function before hepatectomy. We investigated 20 patients undergoing hepatectomy using the clearance rate of indocyanine green (KICG) as a parameter, and compared the predicted postoperative KICG obtained by CT and by transaxial single-photon emission tomographic (SPET) images acquired by 99mTc GSA liver scintigraphy before hepatectomy. In GSA studies, based on time-activity curves for the heart and liver, we compared HH15 (heart activity at 15 min divided by heart activity at 3 min), LHL15 (liver activcity at 15 min divided by heart plus liver activity at 15 min) and KL (obtained from the time-activity curve for the liver) in 103 patients. In 58 patients without increased serum bilirubin, KL was compared with KICG. In four patients, occlusion of the right portal vein was performed with the aim of carrying out secondary hepatectomy, and changes in liver volume were compared between CT and 99mTc GSA liver scintigraphy. The correlation coefficient between the postoperative KICG predicted by CT and the actual postoperative KICG was rather poor, at r = 0.569 (P〈0.05); that between the postoperative KICG predicted by 99mTc GSA liver scintigraphy and the actual postoperative KICG was good, at r = 0.788 (P〈0.01); correlations between KL and HH15 and between KL and LHL15 in 103 patients were very good or good, at r = 0.906 (P〈0.001) and r = 0.807 (P〈0.001), respectively, and that between KL and KICG in 58 patients was very good, at r = 0.916 (P〈0.001). In all four cases of right portal vein occlusion, the remnant liver volume ratio was markedly increased after occlusion in GSA compared with CT, and the postoperative KICG predicted by GSA after occlusion was closer to the actual postoperative KICG than that predicted by CT. It is concluded that 99mTc GSA liver scintigraphy is useful for predicting remnant liver function before hepatectomy and for evaluating changes in regional liver function after occlusion of the portal vein unilaterally.
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  • 60
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    Annals of biomedical engineering 26 (1998), S. 519-525 
    ISSN: 1573-9686
    Keywords: Angiogram ; Microspheres ; Embolization ; Fractal ; Computed tomography ; Artery: coronary ; Temporospatial heterogeneity ; Myocardial perfusion ; Blood volume ; Heart ; Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Spatial heterogeneity of myocardial perfusion has been recognized for many years. Whether this is primarily the result of heterogeneity of parameters such as myocardial metabolism, of intramyocardial mechanical forces, or of vasomotor function within the myocardial microcirculation, is not clear. A practical problem is that it has been almost impossible to measure any two of these parameters simultaneously in the same piece of myocardium so that an unambiguous correlation, much less a cause-and-effect relationship, has been difficult to establish. In this study of six anesthetized pigs, we propose that whole-body computed tomography is a method for providing the simultaneous measurement of heterogeneity of myocardial perfusion (F) and myocardial blood volume (ρ). The first finding was that the empirical relationship ρ=AF+BF0.5 between myocardial blood flow (F) and intramyocardial blood volume (ρ) is maintained over a range of sizes of regions of interest (approximately 1 to 0.125 cm3) within the myocardium of each individual animal despite the spatial heterogeneity of the F and the ρ values. The value of A ranges from 0.014 to 0.021 min and of B ranges from 0.061 to 0.076 ml0.5 g−0.5 min0.5. A second finding was that the pattern of spatial heterogeneity of F and of ρ remained reasonably stable over at least a 1 h period. © 1998 Biomedical Engineering Society. PAC98: 8745Ft, 8759Fm
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  • 61
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    Journal of orofacial orthopedics 59 (1998), S. 17-28 
    ISSN: 1615-6714
    Keywords: Lower wisdom tooth ; Computed tomography ; Panoramic radiography ; Space ratio ; Method of interpretation ; Unterkiefer-Weisheitszahn ; Computertomographie ; Panoramaschichtaufnahme ; Raumverhältnisse ; Auswertungsverfahren
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Von 13 Patienten standen je ein axial geschichtetes Computertomogramm (CT) des Unterkiefers und eine Panoramaschichtaufnahme (Orthophos, Programm P1) zur Verfügung. Die Platzverhältnisse für die Unterkieferweisheitszähne wurden in der P1-Aufnahme metrisch über die Quotientenbildung zweier Strecken bestimmt. Im CT wurden drei M3-Positionen unterschieden: der M3 lag vor dem Ramus mandibulae=ausreichendes Platzangebot, teilweise im Ramus=eingeschränktes Platzangebot, im kaudalen Abschnitt des Ramus=mangelhaftes Platzangebot. Diese M3-Positionen wurden den Weisheitszähnen in der P1-Aufnahme zugeordnet: in bezug zum Ramus und in bezug auf das Lot (L) (eine Vertikale zur Okklusionslinie im projektorischen Schnittpunkt des vorderen Ramusrandes mit dem Schatten der Crista temporalis). Am CT wurde zudem die mesiale Rotation der M3 gemessen und die Beziehung der M3 zu den umgebenden Knochenstrukturen beschrieben. Der Vergleich zwischen CT-Befund und dem Quotienten zeigte, daß für Weisheitszähne mit einem retromolaren Platzangebot im Quotientenbereich über 50% bis unter 100% jede der drei Weisheitszahnpositionen im CT vorkam. Beim Vergleich der M3-Befunde in bezug auf die Ramusüberprojektion in der P1-Aufnahme mit der Beurteilung im CT stimmten 60% der M3 mit dem CT-Befund überein. Wurde der M3 in bezug auf das Lot beurteilt, so erhöhten sich die mit dem CT übereinstimmenden Befunde auf 76%. Diese Befunde sowie die in der P1-Aufnahme nicht erkennbare Mesialrotation der M3 und ihre unterschiedliche Beziehung zur knöchernen Umgebungsstruktur ergaben neue Aspekte, die möglicherweise die M3-Durchbruchsprognose beeinflussen. Die dreidimensionale Betrachtungsweise mit dem CT bietet neue Möglichkeiten für weitere Untersuchungen der M3-Problematik.
    Notes: Summary From 13 patients a computed tomograph (CT-scan) and a panoramic radiograph (Orthophos, program 1, P1) were examined with respect to the spatial conditions of the lower wisdom teeth. In the panoramic radiograph the available space for the third molars of the lower jaw was determined by calculating the ratio (Q) of 2 distances: the mesiodistal crown diameter and the retromolar space. In the axial CT 3 different positions of the third molar were distinguished: third molar located anterior to the ramus mandibulae=sufficient space, partially within the ramus=restricted space, totally within the ramus=deficient space. These positions were compared with the findings in the panoramic radiograph, firstly in relation to the ramus and secondly in relation to a line (L) perpendicular to the occlusal plane at the intersection of the anterior border of the ramus and the crista temporalis. Furthermore, the mesial rotation of the third molar was measured and the relation of the bony structures surrounding the teeth were described. Comparison of the CT results with the quotients of the P1 showed that, for those wisdom teeth molars with an available space above 50% to under 100%, any of the 3 CT gradings was found. Assessing the projection of the ramus over the third molar as seen in the P1, 60% of the P1- and CT-results corresponded. The relation between the line L and the third molar showed coincidence in 76% of all cases. These results and the mesial rotation of the wisdom teeth as well as their different relation to the bony environment are possibly important factors concerning their eruption prognosis. The three-dimensional CT-scan gives new posibilities for further investigations of third-molar problems.
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  • 62
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    Mund-, Kiefer- und Gesichtschirurgie 2 (1998), S. 188-193 
    ISSN: 1434-3940
    Keywords: Schlüsselwörter Dentale Implantologie ; Computertomographie ; Genauigkeit ; Strahlendosis ; Key words Dental implants ; Computed tomography ; Radiation dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Absorbed radiation doses delivered by computed tomography and panoramic radiography were measured in 16 anatomic sites using a head and neck phantom and thermoluminescent dosimetry. The recommended kilovoltage and scan time for dental scanning was reduced step by step, rating the quality of the low-dose scans. A reduction of up to 76% could be achieved without loss of diagnostic accuracy. Measured absorbed radiation dose ranges from 0.30 mGy (thyroid) to 29 mGy (skin) at 187,5 mAs and 1.0 mm-slices (25 mm scanning distance for maxilla, 30 mm for mandible). After reduction to 45 mAs, 0.07 mGy (thyroid) to 6.9 mGy (skin) was measured. Distance measurements on human jaw specimens were compared with corresponding CT image measurements. Average deviation was 0.1– 0.3 mm. A dose reduction of 75% had no effect on the results. However, the doses of CT-scans reduced by 76% exceed by an average factor of 10 the doses of conventional panoramic radiography. Therefore, CT should be reserved for the planning of complex implant treatment in the direct vicinity of the maxillar sinus and nerves and for multiple implant insertion.
    Notes: Die Energiedosis der Spiralcomputertomographie sowie des Orthopantomogramms (OPG) wurde an 16 Positionen im Kopfbereich mit Hilfe von Thermolumineszenzdosimetern und eines Phantomkopfs bestimmt. Die vom Hersteller des Computertomographen empfohlene Röhrenleistung für eine dentale CT wurde schrittweise reduziert. Eine Verminderung der Strahlenbelastung um 76% wurde ohne Verlust an diagnostischer Information erreicht. Die gemessene Energiedosis der Computertomographie betrug 0,30 mGy (Schilddrüse) bis 29 mGy (Hautoberfläche im Strahlengang) bei 187,5 mAs und 1-mm-Schichten (25 mm Scanstrecke im Oberkiefer, 30 mm im Unterkiefer). Bei Reduzierung auf 45 mAs wurden 0,07 mGy (Schilddrüse) bis 6,9 mGy (Hautoberfläche) gemessen. Längenmessungen an gesägten Kieferpräparaten wurden mit korrespondierenden CT-Messungen an einer Workstation verglichen. Die durchschnittliche Meßungenauigkeit betrug hierbei 0,1–0,3 mm. Die Dosisreduzierung der CT um ca. 76% hatte keinen Einfluß auf die Längenmeßgenauigkeit. Allerdings liegen die Energiedosen der um 76% dosisreduzierten CT-Scans noch durchschnittlich um den Faktor 10 über der Energiedosis eines Orthopantomogramms. Die Computertomographie sollte daher der Planung komplexer Implantatversorgungen in Kieferhöhlen- oder Nervennähe sowie multipler Implantationen vorbehalten bleiben.
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  • 63
    ISSN: 1434-5196
    Keywords: Key words Adipocere ; Brain ; Retroorbital fatty ; tissue ; Computed tomography ; Schlüsselwörter Leichenlipid ; Adipocire ; Gehirn ; Retroorbitalfettgewebe ; Computertomographie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Anhand von 3 Beobachtungen aus dem rechtsmedizinischen Sektionsgut werden verschiedene Manifestationsformen von Leichenlipid im Kopfbereich vorgestellt: In einem Fall wurde das gesamte Gehirn nach 6jähriger Wasserliegezeit in gutem Erhaltungszustand vorgefunden. In zwei Fällen war das Retroorbitalfett in Leichenlipid umgewandelt, wobei jeweils Aussparungen im Verlauf der Nn. optici und der Augenmuskeln bestanden. Bei zwei Leichen waren auch die Wangenweichteile partiell in Adipocire transformiert. Vor der autoptischen Schädelöffnung wurden computertomographische Untersuchungen durchgeführt. Das in toto erhalten gebliebene Gehirn zeigte im CT deutlich abgrenzbare Binnenstrukturen; die Dichtemessungen des ehemaligen Hirnparenchyms ergaben Hounsfield-Einheiten im Bereich von Fettmischgewebe. In einem weiteren Fall war lediglich eine amorphe Weichteilmasse darstellbar.
    Notes: Abstract On the basis of three observations from forensic autopsies, different forms of manifestation of adipocere in the head region are presented. In one case the entire brain was found to be well preserved after the body had been immersed in water for 6 years. In two cases the retroorbital fatty tissue had been converted into adipocere, avoiding the Nn. optici and the eye muscles. In two bodies the soft tissue of the cheeks was also partially transformed to adipocere. Before opening the skull at autopsy scans by computed tomography were performed. The brain, which had been preserved in toto, showed clearly definable internal structures by CT and density measurements of the former brain parenchyma showed Hounsfield units in the range of mixed fatty tissue. In another case only an amorphous brain mass could be visualised.
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    Space science reviews 84 (1998), S. 199-206 
    ISSN: 1572-9672
    Keywords: Nuclear reactions ; Nucleosynthesis ; Abundances ; Stars:Evolution ; Interior ; Rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We first recall the observational and theoretical facts that constitute the so-called 3He problem. We then review the chemical anomalies that could be related to the destruction of 3He in red giants stars. We show how a simple consistent mechanism can lead to the destruction of 3He in low mass stars and simultaneously account for the low 12C/13C ratios and low lithium abundances observed in giant stars of different populations. This process should both naturally account for the recent measurements of 3He/H in galactic HII regions and allow for high values of 3He observed in some planetary nebulae. We propose a simple statistical estimation of the fraction of stars that may be affected by this process.
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  • 65
    ISSN: 0894-3230
    Keywords: Menschutkin reaction ; duality of SN1, SN2 mechanisms ; benzyl tosylates ; Yukawa-Tsuno equation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rate data for the Menschutkin reaction between strongly activated Z-substituted benzyl p-toluenesulfonates and Y-substituted N,N-dimethylanilines in acetonitrile at 35 °C fit the equation, kobs  =  k1 + k2 [DMA], which is consistent with concurrent first- and second-order processes. The k1 and k2 values for each substrate were separated based on the above equation. The SN1 rate constant, k1, is unaffected by the nature of the nucleophile, whereas the SN2 rate constant, k2, increased with the electron-donating substituent of the N,N-dimethylaniline. The substituent effect on the k1 values is linearly correlated by the Yukawa-Tsuno equation with ρ  =  -5.2 and r  =  1.3. The unimolecular reaction can be regarded as a classical SN1 mechanism. In contrast, that on the k2 values shows an upward curvature when analyzed by the Brown σ+ treatment. These results are ascribed to the simultaneous and independent occurrence of SN1 and SN2 mechanisms in the present Menschutkin reaction. © 1998 John Wiley & Sons, Ltd.
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  • 66
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    Journal of Physical Organic Chemistry 11 (1998), S. 231-231 
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No Abstract
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  • 67
    ISSN: 0894-3230
    Keywords: calorimetry ; IR spectra ; ketones ; solvation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solution enthalpies of n-hexane, acetone, butan-2-one and octan-2-one in a series of tetrachloromethane-acetonitrile mixtures and the carbonyl stretching absorption frequencies in the IR spectra of these ketones were determined. It was found that over the whole range of concentrations (varying from neat tetrachloromethane up to neat acetonitrile) the solvation enthalpy of these compounds can be obtained additively from the contributions of the alkyl and carbonyl fragments. The solvent effect on the solvation enthalpy of the carbonyl group was found to be satisfactorily correlated with the corresponding IR frequency shifts of the C=O group. It was also found that the sensitivities of the carbonyl IR frequencies to the solvent composition are different for various ketones. From both IR and calorimetric data, the preferential solvation parameters were evaluated. The differences between the IR spectroscopic and calorimetric data are discussed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 261-272 
    ISSN: 0894-3230
    Keywords: 1-substituted 2-pyrrolidinones ; C=O stretching frequencies ; solvent effects ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In an effort to model solute-solvent interactions, the C=O stretching frequencies of five 1-substituted 2-pyrrolidinones and four other carbonyl-containing compounds were measured for 30 common solvents. These were then correlated with four empirical parameter sets and one theoretical (computational) parameter set. While an empirical parameter set gave the best correlation equations, the theoretical parameter equations are physically and statistically significant. Solvent volume, polarizability and hydrogen bond donor acidity (capacity) terms are significant in the correlation equations. © 1998 John Wiley & Sons, Ltd.
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  • 69
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    Journal of Physical Organic Chemistry 11 (1998), S. 232-240 
    ISSN: 0894-3230
    Keywords: P - S bond cleavage ; hydroperoxidolysis ; nerve agent VX ; molecular orbital calculations ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The P - S bond cleavage process in the hydroperoxidolysis of a model system for the nerve agent VX was studied using ab initio and semiempirical molecular orbital methods. Aqueous solvation effects were included through single-point calculations using the semiempirical SM5.2PD/A continuum solvation model and geometries optimized at the HF/MIDI! level of theory. The predominant pathway for P - S bond cleavage involves pseudorotation of a low-energy trigonal bipyramidal intermediate followed by apical ligand ejection. In aqueous solution, the free energy barriers for these processes are found to be 14.3 and 4.6 kcal mol-1, respectively, with electronic energies calculated at the MP2/cc-pVDZ//HF/MIDI! level of theory. By comparison with another continuum model of solvation (PCM), it is concluded that the SM5.2PD/A model performs well even for hypervalent phosphorus species, in spite of not having included any such molecules in the model's parameterization set. © 1998 John Wiley & Sons, Ltd.
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  • 70
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    Journal of Physical Organic Chemistry 11 (1998), S. 407-410 
    ISSN: 0894-3230
    Keywords: gas-phase thermolysis ; N-methyl-N-phenyl-tert-butylsulfenamide ; morpholinyl-tert-butylsulfenamide ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: N-Methyl-N-phenyl-tert-butylsulfenamide (MPSA) and morpholinyl-tert-butylsulfenamide (MOSA) were thermolyzed in a stirred-flow reactor at temperatures of 340-390 °C and pressures of 7-13 Torr, using toluene as carrier gas, at residence times of 0.3-1.3 s. Isobutene was formed in 99% yield through first-order reactions having the following Arrhenius parameters (A,s-1, Ea, kJ mol-1): MPSA, log A  =  12.41 ± 0.02, Ea  =  158.8 ± 0.2; MOSA, log A  =  12.91 ± 0.22, Ea  =  159 ± 3. It is proposed that the elimination of isobutene takes place by unimolecular reaction mechanisms involving polar, four-center cyclic transition states, forming S-unsubstituted thiohydroxylamines as co-products. Thermochemical parameters, estimated by semiempirical AM1 calculations, are reported for the latter and for the parent molecules. © 1998 John Wiley & Sons, Ltd.
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  • 71
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    Journal of Physical Organic Chemistry 11 (1998), S. 411-418 
    ISSN: 0894-3230
    Keywords: 2,2′-bisbenzimidazolyl ; tautomerism ; NMR ; semi-empirical calculations ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A dynamic NMR study of the tautomerism of 2,2′-bisbenzimidazolyl in DMSO-d6 and a mechanistic interpretation of the process, based on a stepwise, single-proton transfer and formation of a zwitterionic intermediate, are presented. This interpretation is substantiated by semi-empirical calculations of the postulated intermediate and transition state, that yield results which are compared with previous studies on related aliphatic systems. © 1998 John Wiley & Sons, Ltd.
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  • 72
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    Journal of Physical Organic Chemistry 11 (1998), S. 397-406 
    ISSN: 0894-3230
    Keywords: bond dissociation energy ; acidity ; phenylsulfenylamides ; phenylsulfenylanilides ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acidities and bond dissociation energies (BDEs) of the N-H bond in two phenylsulfenylamides, PhSNHBz and PhSNH-t-Bu, and four phenylsulfenylanilides, 4-GC6H4NHSPh, where G  =  MeO, H, Br and CN, were measured in order to compare the effects of substituents on acidities and BDEs of N - H bonds with those of C - H bonds. The effects of PhS groups on acidities and BDEs in a series of C - H acids were found to be comparable to those on acidities and BDEs of PhS in a similar series of N - H acids. Comparisons were also made of the effects of changing the oxidation state of sulfur in the series PhS, PhSO and PhSO2 on the acidities and BDEs of adjacent N - H and C - H bonds in weak acids. Hammett-type plots of pKHA values for phenyl benzyl sulfones (4-GC6H4CH2SO2Ph) and phenylsulfenylanilides (4-GC6H4NHSPh) were linear vs σp- values. A linear plot was obtained and explained for a plot of BDE of the N - H bonds in remotely substituted phenylsulfonylanilides with σ+ values. Plots of BDEs vs Eox(A-) were also linear for 4-substituted phenylsulfenylanilides (4-GC6H4NHSPh), phenylsulfonylanilides (4-GC6H4NHSO2Ph) and phenyl benzyl sulfones (4-GC6H4CH2SO2Ph). © 1998 John Wiley & Sons, Ltd.
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  • 73
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    Journal of Physical Organic Chemistry 11 (1998), S. 387-391 
    ISSN: 0894-3230
    Keywords: α-diamides ; 17O NMR ; conformation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 17O NMR spectra of several α-diamides were obtained at natural isotopic abundance in acetonitrile solution in order to study the conformations of these compounds in solution. The 17O NMR shifts vary with the intercarbonyl dihedral angle α in a sense opposite to that observed for α-diketones. © 1998 John Wiley & Sons, Ltd.
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  • 74
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    Journal of Physical Organic Chemistry 11 (1998), S. 392-396 
    ISSN: 0894-3230
    Keywords: 8-azaadenine ; tautomerism ; theoretical study ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The prototropic tautomerism of 8-azaadenine (azaade) was studied theoretically by means of ab initio methods, in both the gas phase and aqueous solution. A number of tautomeric forms were not included in the calculations after applying a stepwise elimination procedure based on both AM1 and HF/6-31G* energy values. The tautomers 9H-azaade, 8H-azaade and 7H-azaade survived to this elimination and their optimized geometries and energies were calculated at the MP2/6-31*//HF/6-31G* level. To include the solvent effects, two self-consistent reaction field method were used: (1) Onsager's SCRF with multipolar expansion up to the hexadecapolar term and (2) the isodensity polarizable continuum method (IPCM). Both methods produce similar results, although the latter represents better the situation in aqueous solution. The stability order in solution, 8H- 〉 9H- 〉 7H-azaade, differs slightly from that found in the gas phase, implying that in general the electrostatic effects in solution are important, but the intrinsic stability of these species in the gas phase overcomes the solvent effect. © 1998 John Wiley & Sons, Ltd.
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  • 75
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    Journal of Physical Organic Chemistry 11 (1998), S. 377-377 
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
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  • 76
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    Journal of Physical Organic Chemistry 11 (1998), S. 419-425 
    ISSN: 0894-3230
    Keywords: 5-nitro-5′-dimethylamino-2,2′-bisthiophene ; π* probe dye ; cyclic voltammetry ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Cyclic voltamograms of the solvatochromic dye 5-nitro-5′-dimethylamino-2,2′-bisthiophene (1), introduced recently as a sensitive π* probe, were recorded in different solvents. An EPR spectrum of the anionic radical of 1 in DMSO was obtained and compared with other spectra of analogous substituted bisthiophene radicals. It was found that the presence of a donor- acceptor pair of substituents in 1-⋅ reduces significantly the rotational barrier of the radical compared with the unsubstituted bithienyl radical anion 2-⋅. This is the result of an electronic repulsion between the donor ring fragment and the added electron in the coplanar radical, which does not exist in 2-⋅. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
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  • 77
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    Keywords: calix[4]resorcinarenes ; organophosphorus compounds ; solvatophobic interactions ; host-guest complexation ; high-performance liquid chromatography ; x-ray analysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Reversed-phase high-performance liquid chromatography [LiChrosorb RP-18,UV detection at 254 nm and acetonitrile-water (86:14,v/v) as mobile phase] was applied to studies of the host-guest complexation of tetraalkylcalix[4]resorcinareneoctols and their upper rim phosphoryl, sulfonyl and dialkylaminomethyl derivatives with some aromatic guests in the mobile phase. It was shown that the formation of the inclusion complexes results in changes in the retention of aromatic guests and improves their separation. Stability constants of the complexes were calculated from the dependences of the l/k′ values of the aromatic guest on the concentration of the calix[4]resorcinarene in the mobile phase. The molecular structure of 4,6,16,18-tetrahydroxy-10,12,22,24-tetrakis(dipropoxyphosphoryloxy)-2,8,14,20-tetramethylcalix[4]resorcinarene (12) was determined. Crystal data for 12 are P21/n, a  =  16.708(9) Å, b  =  18.683(6) Å, c  =  20.243(5) Å, β  =  95.75(3)°, V  =  6287(4) Å3 and Z  =  4. Compound 12 exists in a boat conformation, in which two opposite unsubstituted resorcinol rings of the macrocyclic skeleton lie in the plane formed by four methine bridges and two diphosphorylated rings are perpendicular to the plane. © 1998 John Wiley & Sons, Ltd.
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  • 78
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    Journal of Physical Organic Chemistry 11 (1998), S. 378-386 
    ISSN: 0894-3230
    Keywords: alkylboronic acids ; arylboronic acids ; ab initio ; MM3 ; molecular mechanics ; force field parameters ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The boronic acid functional group has been incorporated into various biologically important compounds. In order to study this class of compounds better with molecular mechanics, five alkyl- and arylboronic acids were calculated using ab initio methods (Spartan) at the RHF/6-31G* level. MM3 force field parameters were developed based on the theoretically calculated geometries, vibrational spectra, and torsional profiles. © 1998 John Wiley & Sons, Ltd.
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  • 79
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    Keywords: γ-lactones ; base-catalysed hydrolysis ; reactivity-structure correlations ; isobenzofuranones ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rate coefficients were measured for the base-catalysed hydrolysis of a series of substituted 3-(phenoxy- or thiophenoxymethylene)-(Z)-1(3H)-isobenzfuranones (3-phenoxy- or thiophenoxymethylenephthalides) in 70% (v/v) aqueous dioxane at 30.0 °C, in addition to the carbonyl stretching frequencies in chloroform and tetrachloromethane following deconvolution and band separation, when required. The Hammett reaction constants for the alkaline hydrolysis of the 3-/4-substituted phenoxy and thiophenoxy series are ca 0.75 and 1.10, respectively. These results are related to electrostatic field and resonance effects. Successful correlations between the carbonyl stretching frequencies and substituent constants and the rates of alkaline hydrolysis were found. Computational studies using the semi-empirical AM1 method correctly model both the details of the mechanistic pathway and the substituent effects. © 1998 John Wiley & Sons, Ltd.
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  • 80
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    Journal of Physical Organic Chemistry 11 (1998), S. 437-447 
    ISSN: 0894-3230
    Keywords: inductive constants ; theoretical estimation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new model of the inductive effect is proposed, allowing highly accurate theoretical calculations of inductive constants for a diversity of substituents, using a simple and readily available system of mathematics. According to this approach, the inductive effect of a substituent is considered in terms of the additive influence of its constituent atoms. A constant inherent capacity for inductive interaction with a reactive center (with a four-coordinate carbon atom chosen for such a center), represented by an atomic constant σA, is ascribed to each atom. Values of σA for a wide variety of atoms are determined, and their physical meaning is revealed to elucidate to a certain extent the physical nature of the inductive effect. In addition, the proposed model permits the convenient use in calculations of group constants σG characterizing the inductive power of groups. Values of σG are determined for molecular fragments that are most widely dealt with in organic chemistry, and the use of σA or σG constants and of their superposition is shown to have, in most cases, little or no effect on the accuracy and reproducibility of the results obtained. It is also shown that, in terms of the developed approach, the inductive effect of a substituent is closely associated with its conformation. Theoretical inductive constants were calculated for 427 organic, aromatic, organometallic and charged substituents, and they showed perfect correlation with the corresponding experimental values. © 1998 John Wiley & Sons, Ltd.
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  • 81
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    Journal of Physical Organic Chemistry 11 (1998), S. 448-454 
    ISSN: 0894-3230
    Keywords: mandelic acid ; alkaline permanganate ; oxidation ; kinetics ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the oxidation of mandelic acid (MA) by permanganate in aqueous alkaline medium at a constant ionic strength of 1.0 mol dm-3 were studied spectrophotometrically. The reaction shows first-order kinetics in [permanganate ion] and fractional order dependences in [MA] and [alkali]. Addition of products, manganate and aldehyde have no significant effect on the reaction rate. An increase in ionic strength and a decrease in dielectric constant of the medium increase the rate. The oxidation process in alkaline medium under the conditions employed in the present investigation proceeds first by formation of an alkali permanganate complex, which combines with mandelic acid to form another complex. The latter decomposes slowly followed by a fast reaction between the free radical of mandelic acid and another molecule of permanganate to give products. The reaction constants involved in the mechanism were derived. There is good agreement between the observed and calculated rate constants under different experimental conditions. The reaction was studied at different temperatures and activation parameters were computed with respect to the slow step of the proposed mechanism. © 1998 John Wiley & Sons, Ltd.
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  • 82
    ISSN: 0894-3230
    Keywords: Selective arylation ; exocyclic N-position ; 2-pyrimidylnitrenium ion ; tetrazolo[1,5a]pyrimidine ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photo-reactions of tetrazolo[1,5-a]pyrimidine (1) with benzene (2a) and substituted benzenes (2b-f) in the presence of trifluoroacetic acid (TFA) gave 2-(2-, 3- and 4-substituted anilino)pyrimidines (3-5) together with 2-aminopyridine (6) and biphenyl (7) or diarylmethanes (8b, 8c and 8e). From the effect of heavy-atom solvent on the reactions, it is reasonable to assume that 3-5 are formed via a singlet species, but 6-8 via a triplet species. The intermediacy of 2-pyrimidylnitrenium ion is consistent with the evidence derived by the above effect, by a Hammett plot with ρ = -2.9 and by effects of solvent nucleophilicity and counter-anions. The selective exocyclic N-arylation giving 3-5 is discussed. © 1998 John Wiley & Sons, Ltd.
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  • 83
    ISSN: 0894-3230
    Keywords: 3-methyl-2, 4-diphenyl-3-azabicyclo[3.3.1]nonan-9α-ol esters ; analgesics ; synthesis ; structure ; conformation ; pharmacological assays ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of esters derived from 3-methyl-2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9α-ol (1) was synthesized and studied by 1H and 13C NMR spectroscopy, and the crystal structure of 3-methyl-2,4-diphenyl-9α-(3,5-dimethylbenzoyloxy)-3-azabicyclo[3.3.1]nonane (2) was determined by x-ray diffraction. The compounds studied display in CDCl3 a preferred flattened chair-chair conformation. This bicycle conformation is similar to that found for 2 in the crystal state. Pharmacological assays on mice were performed to evaluate drug-induced behavioral alteration, peripheral or central acute toxicity and analgesic activity. © 1998 John Wiley & Sons, Ltd.
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  • 84
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    Journal of Physical Organic Chemistry 11 (1998), S. 101-108 
    ISSN: 0894-3230
    Keywords: encounter complexes ; 1-cyanonaphthalene ; norbornadiene ; stereospecific ; nucleophilic trapping ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photo-induced electron donor-acceptor reactions between 1-cyanonaphthalene (CNN) and norbornadiene (N) generate products of several structure types. Methanol adducts (1-3) formed in polar solvents are rationalized via the radical cation, N+·, and stereospecific (exo-) nucleophilic attack by methanol. In less polar solvents, CNN and N form [2 + 2]-cycloadducts, exclusively on the exo-face of N. In non-polar solvents containing methanol, CNN, N and methanol combine to form 1:1:1 adducts, containing the sensitizer on the endo- and the methoxy groups on the exo-face. The formation of these products is rationalized via the trapping of encounter complexes of different geometries. Any rearrangement of the norbornenyl system can be eliminated, since neither tricyclyl nor 7-methoxynorbornenyl structures are formed. Apparently, the alcohol captures an endo-encounter complex of CNN and N by attack from the exo-face, similar to the attack of methanol on N+·. © 1998 John Wiley & Sons, Ltd.
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  • 85
    ISSN: 0894-3230
    Keywords: aromaticity ; Diels-Alder transition states ; Diels-Alder adducts ; reaction mechanism ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Semiempirical, ab initio and DFT investigations on the mechanism of the Diels-Alder reactions of a set of masked dienes (ring-fused dienes), viz. o-quinodimethane, anthracene and α-vinylnaphthalene, with ethylene, and reactions of α-vinylnaphthalene with maleic anhydride and p-benzoquinone were performed with a view to understanding the role of masking factors on the activation and reaction energies. The reactions were found to occur in a concerted fashion through synchronous transition states (TSs) in the first two reactions and through asynchronous TS in the other case. Of the compounds studied, o-quinodimethane is the most reactive diene both in a kinetic and a thermodynamic sense. α-Vinylnaphthalene reacts faster with maleic anhydride than p-benzoquinone, as expected, and two possible stereoselective TSs, one endo and the other exo, have been located for the reactions of α-vinylnaphthalene with the above dienophiles. Calculations show that the relative gain or loss of aromatic stabilization of the benzonoid ring in the transition state and in the product seems to play a major role in the kinetic and thermodynamic control of these reactions. © 1998 John Wiley & Sons, Ltd.
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  • 86
    ISSN: 0894-3230
    Keywords: methylbenzoic acids ; infrared spectra ; conformation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared spectra of all isomers of polymethyl-substituted benzoic acids were recorded in the carbonyl and hydroxyl regions in tetrachloromethane at various concentrations and interpreted in terms of conformation. According to a plot of ν(C=O) of the monomeric form vs Hammett substituent constants σ, these compounds may be classified into two classes. Derivatives with none or only one methyl group in the ortho position are concluded to exist in an equilibrium of two planar conformations, unless the equilibrium is degenerate. Derivatives with two ortho-situated methyl groups are concluded to take up one non-planar conformation. These findings are supported by the shape of the hydroxyl and carbonyl bands, which are unsymmetrical in the former class, although they could not be reliably separated into bands pertinent to the individual conformers. This conclusion is at variance with the common interpretation which has invariably ascribed to these and similar ortho derivatives non-planar conformations with a variable torsional angle. © 1998 John Wiley & Sons, Ltd.
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  • 87
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    Journal of Physical Organic Chemistry 11 (1998), S. 149-154 
    ISSN: 0894-3230
    Keywords: P - C bond cleavage ; phosphoranyl radicals ; organophosphonate biodegradation ; ab initio calculations ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Barrier heights for P - C bond homolysis in P-hydroxy-P-methyl-P,P-dioxophosphoranyl and P,P,P-trihydroxy-P-methylphosphoranyl were calculated using well correlated levels of electronic structure theory. The best estimate for the difference in barriers between the two indicates that homolysis is more facile for P,P,P-trihydroxy-P-methylphosphoranyl by roughly 9 kcal mol-1. This result suggests that bacterial pathways leading to P - C bond cleavage in organophosphonate derivatives will preferentially proceed via initial one-electron reduction of substrates rather than oxidation. © 1998 John Wiley & Sons, Ltd.
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  • 88
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    Journal of Physical Organic Chemistry 11 (1998), S. 201-208 
    ISSN: 0894-3230
    Keywords: indolizines ; cycloaddition ; reaction mechanism ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The peculiarities of [8+2] cycloaddition reactions of indolizines with dienophiles are reviewed. Quantum chemical SINDO1, AM1 and ab initio calculations of transition states were performed for [8+2] cycloaddition reactions of indolizine and 6-nitroindolizine with a series of alkenes with donor and acceptor groups. The calculations predict a dipolar cycloaddition mechanism (electrophilic addition and ring closure) for reactions of indolizine and 6-nitroindolizine with nitroethylene. For the reaction of 6-nitroindolizine with N,N-dimethylaminoethylene, the predicted mechanism corresponds to a previously unknown ‘inverse’ dipolar cycloaddition (nucleophilic addition and ring closure). © 1998 John Wiley & Sons, Ltd.
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  • 89
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    Journal of Physical Organic Chemistry 11 (1998), S. 115-124 
    ISSN: 0894-3230
    Keywords: cross-interaction constants ; gas-phase nucleophilic substitution reactions ; PM3 MO ; benzyl chlorides ; phenoxides ; thiophenoxides ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Gas-phase nucleophilic substitution reactions of Y-benzyl chlorides with X-phenoxide and X-thiophenoxide nucleophiles were investigated theoretically using the PM3 semi-empirical MO method. The Leffler-Grunwald rate-equilibrium and Brønsted correlations predict that the degree of bond formation in the transition state (TS) is approximately 45 and 40% on the reaction coordinate for the phenoxides and thiophenoxides, respectively. For a weaker nucleophile, a later TS is obtained with an increased bond making and breaking. The variation of the TS structure with substituents in the nucleophile is thermodynamically controlled and is well correlated by rate-equilibrium relationships. In contrast, the TS variation (a tighter TS) with substituent (for a stronger acceptor Y) in the substrate is dependent only on variations of the intrinsic barrier and so cannot be correlated by such thermodynamically based rate-equilibrium relationships. The gas phase ρX and ρY values are much greater in magnitude than those in solution. A similar gas-phase theoretical cross-interaction constant, ρXY (ca -0.60), is obtained for both phenoxides and thiophenoxides, which is in good agreement with the experimental value (-0.62) for the thiophenoxide reactions in MeOH at 20.0 °C. The oxy and sulfur anion bases lead to a similar TS structure, but a lower reactivity for the former is due to a greater endothermicity of the reaction. A relatively wide range variation of the reaction energies, ΔG°, can be ascribed to the loss of resonance stabilization of anion nucleophiles upon product formation. © 1998 John Wiley & Sons, Ltd.
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  • 90
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    Journal of Physical Organic Chemistry 11 (1998), S. 171-176 
    ISSN: 0894-3230
    Keywords: acetaldehyde ; oxidation ; periodate ; osmium (VIII) catalysis ; ruthenium (III) catalysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Os(VIII) and Ru(III) catalysis of the periodate oxidation of acetaldehyde in aqueous alkaline medium was investigated. The catalytic efficiency is Ru(III)〈Os(VIII). The product of oxidation in both cases is acetate and IO3-. The stoichiometry is the same in both catalyzed reactions, i.e. [IO4-]:[CH3CHO] = 1:1. Probable mechanisms are proposed and discussed. The reaction constants involved in the mechanisms are derived. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
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  • 91
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 223-229 
    ISSN: 0894-3230
    Keywords: Solvolysis ; Grunwald-Winstein-type analysis ; Hammett-type analysis ; YxBnCl scale ; 1-aryl-1-phenylmethyl cations ; Mulliken population analysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rate constants of solvolysis of α-tert-butyl(2-naphthyl)methyl chloride (1), 9-fluorenyl chloride (2) and a series of monosubstituted benzhydryl chlorides (3) in a wide range of solvents were measured. Grunwald-Winstein-type correlation analysis of log k for 2 and 3 against YBnCl, with or without nucleophilicity N, yielded less satisfactory linear correlations than that against log k(1). A new scale of solvent ionizing power, YxBnCl, for the correlation of solvolytic reactivities of benzylic chlorides with extended charge delocalization based on log k(1) was developed. Application to the mechanistic study suggested the solvolysis of 2 and 4-nitrobenzhydryl chloride were non-limiting. Hammett plots against σ+ constants exhibited more negative ρ values in less nucleophilic solvents. In a benzhydryl chloride containing a strong deactivating substituent, such as 4-nitro, the positive charge delocalizes mainly over the unsubstituted ring in the cationic transition state. The uneven charge distribution was also confirmed by Mulliken population analysis at the level of the RHF/6-31G*//RHF/3-21G(*) basis set for cations. Comparison of the results of correlation analysis using the equation log(k/k0) = mY vs the equation log(k/k0) = mY+hI, and using the equation log(k/k0) = mY+lN vs the equation log(k/k0) = mY+lN+hI indicated the use of YBnCl or YxBnCl could give a better understanding of solvolytic mechanisms than the combinatorial use of YCl and I. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
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  • 92
    ISSN: 0894-3230
    Keywords: Solvent-solute interactions ; β-carotene ; electronic absorption spectrum ; solvent effects ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solvent effects on the wavenumber of the maximum of the longest wavelength electronic absorption band of all-trans-β-carotene were determined in 34 solvents. Together with results from previous studies, a data set for 51 solvents, mostly non-hydrogen bond donors, was constructed. This information was analyzed in terms of reaction field models and also showed its value for correlation purposes when used either alone or in combination with standard empirical solvent polarity-polarizability scales. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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  • 93
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 177-184 
    ISSN: 0894-3230
    Keywords: nitro derivatives of phenols ; pyrolysis initiation reactions ; impact sensitivity ; UHF-SCF-AM1 MO method ; activation energy. ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The UHF-SCF-AM1 MO method was applied to the study of two kinds of pyrolysis reactions of six nitro derivatives of phenols (homolysis reaction by rupture of the C - NO2 bond into radicals and isomerization reaction involving phenolic hydrogen transferring to oxygen on the NO2 group). The molecular geometries of reactants, transition states and products were fully optimized. The potential energy curves and activation energies were first obtained. The results show that this category of compounds is more easily initiated via isomerization reactions than by homolysis reactions. The parallel relationship among the Wiberg bond order of the pyrolysis-initiation H - O bond in the molecule of a reactant, the activation energy of the isomerization reaction breaking the H - O bond and impact sensitivity of the reactant gives ‘the principle of the smallest bond order’ (PSBO) powerful support. The sensitizing effect of a phenol group was elucidated based on calculation results. The different influences of OH and NO2 groups on the heat of formation of a molecule are discussed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
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  • 94
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 216-222 
    ISSN: 0894-3230
    Keywords: o-carboxybenzohydroxamic acid ; phthalic anhydride ; phthalic acid ; hydrolysis ; intramolecular acid catalysis ; kinetics ; activation parameters ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Phthalic anhydride was detected spectrophotometrically in the hydrolysis of o-carboxybenzohydroxamic acid (OCBA) in CH3CN-H2O solvent containing 0.03 mol dm-3 HCl. Pseudo-first-order rate constants (k1) for hydrolysis of OCBA are almost independent of the change in CH3CN content from 10 to 80% (v/v) in mixed aqueous solvents. The rate constants k1 are more than 10-fold larger than the corresponding rate constants for hydrolysis of phthalamic acid. These observations are explained in terms of a mechanism slightly different from the mechanism for hydrolysis of phthalamic acid. The activation parameters, ΔH* and ΔS*, are not affected appreciably by an increase in CH3CN content from 10 to 80% in mixed aqueous solvents. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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  • 95
    ISSN: 0894-3230
    Keywords: solute-solvent interactions ; solvent-solvent interactions ; binary solvents ; alcohol-water mixtures ; water structure ; solvatochromic indicators ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A preferential solvation model that takes into account the enhancement of the structure of water when small amounts of alcohol are added was applied to solvatochromic data for binary mixtures of water with 2-methylpropan-2-ol, propan-2-ol, ethanol and methanol. Application of the model allows the calculation of the effect of the enhancement of the water structure on solvatochromic solvent properties. It is demonstrated that the enhancement of water structure increases the solvent dipolarity/polarizability and hydrogen-bond donor acidity and decreases the solvent hydrogen-bond acceptor basicity. The effect decreases in the order 2-methylpropan-2-ol-water, propan-2-ol-water, ethanol-water and methanol-water. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
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  • 96
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 157-170 
    ISSN: 0894-3230
    Keywords: heterolytic bond dissociation energy ; carbon-carbon σ bonds ; hydrocarbons ; structural dependence ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The coordination of a resonance-stabilized hydrocarbon cation and anion yielded a series of unprecedented hydrocarbons, which are susceptible to thermal heterolytic cleavage of carbon-carbon σ bonds in polar media, generating the original ions under reversible conditions. When the component ions were sufficiently stabilized, some ion pairs were even isolated as solids, thus providing the first examples of hydrocarbon salts. The direct observation of the heterolysis by means of spectroscopy permitted reliable thermodynamic treatments of the observed degree of ionic dissociation. Correlation of the free energy of heterolysis with solvent dielectric constants and parameters of ion stabilities such as pKHA, pKR+ and redox potentials revealed the importance of the thermodynamic stabilities of ions, the degree of solvation and steric congestion in the starting molecule as major controlling factors in the heterolysis. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 16 Ill.
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  • 97
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 273-276 
    ISSN: 0894-3230
    Keywords: N,N-diphenylcarbamoylpyridinium ion ; solvolysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solvolyses of the N,N-diphenylcarbamoylpyridinium ion are subject to specific and/or general base catalysis, which can be eliminated by addition of perchloric acid or increased, especially in fluoroalcohol-containing solvents, by addition of pyridine. The uncatalyzed solvolyses in aqueous methanol and aqueous ethanol involve a weakly nucleophilically assisted (l  =  0.22) heterolysis and the solvolyses in the pure alcohols are anomalously slow. © 1998 John Wiley & Sons, Ltd.
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  • 98
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 209-215 
    ISSN: 0894-3230
    Keywords: securinine ; cationic micelles ; anionic micelle ; non-ionic micelle ; alkaline hydrolysis ; kinetics ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of micelles of cetyltrimethylammonium bromide (CTABr), tetradecyltrimethylammonium bromide (TTABr), sodium dodecyl sulfate (SDS) and polyoxyethylene 10 lauryl ether (C12E10) on the rates of alkaline hydrolysis of securinine were studied at a constant [-OH] (0.05 M). An increase in the total concentrations of CTABr, TTABr, SDS and C12E10 from 0.0 to 0.2 M causes a decrease in the observed pseudo-first-order rate constants (kobs) by factors of ca 2.5, 3, 7 and 4, respectively. The observed data are explained in terms of pseudophase and pseudophase ion-exchange (PIE) models of micelle. The binding constants, KS, of securinine with SDS, C12E10, CTABr and TTABr micelles are 32.4, 14.8, 22.1, and 9.1 M-1, respectively. The magnitudes of the second-order rate constants, kM, for the reactions in the micellar pseudophase are negligible compared with the corresponding rate constant, kW, for the reaction occurring in the aqueous pseudophase for CTABr, TTABr, SDS and C12E10. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
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  • 99
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 277-282 
    ISSN: 0894-3230
    Keywords: colloidal CdS-induced photochemical reactions ; photocatalytic reactions ; photooxidation ; 2-methylindole ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 2-Methylindole (2-MI) is adsorbed on the surface of colloidal CdS particles with an adsorption intensity of 0.6 × 103 dm3 mol-1. A new emission band at 530 nm is produced by forming an exciplex between excited CdS and 2-MI and the red emission due to CdS is simultaneously quenched. The emission maxima of green bands for different indoles increase in the order indole 〈 tryptophan 〈 2-MI 〈 3-MI and are observed at 508, 520, 530 and 540 nm, respectively. The shift in emission maxima is related to the oxidation potential of these substrates. The irradiation of an aerated reaction mixture containing CdS and 2-MI with visible light induces the oxidation of adsorbed 2-MI by photogenerated holes to produce 2-methyl-3-indolinone and 2-acetamidobenzaldehyde. The latter product is formed due to oxidative C - C bond cleavage of the pyrrole ring. The reactivity of trapped holes towards the adsorbed 2-MI is evidenced by a decrease in the lifetime of the red emission of CdS in the presence of 2-MI. In this reaction the possibility of the participation of singlet oxygen is ruled out. A general mechanism of CdS-induced oxidation of indoles is discussed. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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  • 100
    ISSN: 0894-3230
    Keywords: crown dithioether ; conformational analysis ; multicomponent equilibrium ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solid-state molecular structure and the conformational behaviour in solution of the 12-membered crown dithioether 8-methyl-1,4-dioxa-7,10-dithiacyclododecane-5,12-dione were studied by x-ray crystallography, 1H and 13C NMR spectroscopy and molecular mechanics. The conformational rigidity of some constituent structural fragments allowed a detailed analysis of the structure and distribution of the conformers. A protocol for studies of multiconformational equilibrium was developed by means of the combined use of structure calculations and dynamic NMR measurements. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
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