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  • 1995-1999  (646)
  • 1998  (646)
  • Numerical Methods and Modeling  (582)
  • Computed tomography
  • Nuclear reactions
  • 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.
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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.
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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.
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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.
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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.
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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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    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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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1-24 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We study the large time asymptotics of solutions u(x, t) of the wave equation with time-harmonic force density f(x)e-iωt, ω≥0, in the semi-strip Ω= (0, ∞)×(0, 1) for a given f∊C∞0(Ω). We assume that u satisfies the initial condition u=(∂/∂t)u=0 for t=0 and the boundary conditions u=0 for x2=0 and x2=1, and (∂/∂x1)u=αu for x1=0, with given α, -π≤α〈∞. Let Dα be the self-adjoint realization of -Δ in Ω with this boundary condition. For -π≤α〈0, Dα has eigenvalues λj=π2j2-α2, j=1, 2, … For j≥2 these eigenvalues are embedded in the continuous spectrum of Dα, σc(Dα)=[π2, ∞]. For α≥0, Dα has no eigenvalues. We consider the asymptotic behaviour of u(x, t), t→∞, as a function of α. In the case α=0 resonances of order √t at ω=πj, j=1, 2, …, were found in References 5 and 10. We prove that for α=-π there is a resonance of order t2 for ω=0 and resonances of order t for every ω〉0 (note that 0 is an eigenvalue of D-π). Moreover, for -π〈α〈0 there are resonances of order t at ω=√λj. The resonance frequencies are continuous functions of α for -π〈α〈0 and tend to πj, j=1, 2, … as α goes to zero.On the contrary in the case α〉0 there are no real resonances in the sense that the solution remains bounded in time as t→∞. Actually in this case, the limit amplitude principle is valid for all frequencies ω≥0. This rather striking behaviour of the resonances is explained in terms of the extension of the resolvent R(κ)=(Dα-κ2)-1 as a meromorphic function of κ into an appropriate Riemann surface. We find that as α crosses zero the real poles of R(κ) associated with the eigenvalues remain real, but go into a second sheet of the Riemann surface. This behaviour under perturbation is rather different from the case of complex resonances which has been extensively studied in the theory of many-body Schrödinger operators where the (real) eigenvalues embedded in the continuous spectrum turn under a small perturbation into complex poles of the meromorphic extension of the resolvent, as a function of the spectral parameter κ2. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 117-128 
    ISSN: 0170-4214
    Keywords: third-grade fluid ; existence ; uniqueness ; classical solution ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The global existence and uniqueness of classical solution of steady motions of a third-grade fluid provided assumptions on positivness of μ (coefficient of viscosity) and α1, γ (material coefficients) is proved. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 227-249 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: Integral equations associated with the basic boundary value problems for the Laplace and Stokes equations are considered. The integral operators for these integral equations are interpreted as the pseudodifferential operators, and their principal symbols are calculated. The symbols are obtained in terms of the principal curvatures and the coefficients of the first quadratic form of the boundary. As a consequence, the initial approximation is suggested for the iterative methods solving the integral equations. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 327-359 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The boundary integral equation method is used to prove the convergence of the Drude-Born-Fedorov equations with variable coefficients, possibly non-smooth, to Maxwell's equations as chirality admittance tends to zero. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 565-588 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: New explicit stability conditions are derived for a linear integro-differential equation with periodic operator coefficients. The equation under consideration describes oscillations of thin-walled viscoelastic structural members driven by periodic loads. To develop stability conditions two approaches are combined. The first is based on the direct Lyapunov method of constructing stability functionals. It allows stability conditions to be derived for unbounded operator coefficients, but fails to correctly predict the critical loads for high-frequency excitations. The other approach is based on transforming the equation under consideration in such a way that an appropriate ‘differential’ part of the new equation would possess some reserve of stability. Stability conditions for the transformed equation are obtained by using a technique of integral estimates. This method provides acceptable estimates of the critical forces for periodic loads, but can be applied to equations with bounded coefficients only. Combining these two approaches, we derive explicit stability conditions which are close to the Floquet criterion when the integral term vanishes. These conditions are applied to the stability problem for a viscoelastic bar compressed by periodic forces. The effect of material and structural parameters on the critical load is studied numerically. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 653-664 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In order to maintain spectrally accurate solutions, the grids on which a non-linear physical problem is to be solved must also be obtained by spectrally accurate techniques. The purpose of this paper is to describe a pseudospectral computational method of solving integro-differential systems with quadratic performance index. The proposed method is based on the idea of relating grid points to the structure of orthogonal interpolating polynomials. The optimal control and the trajectory are approximated by the m th degree interpolating polynomial. This interpolating polynomial is spectrally constructed using Legendre-Gauss-Lobatto grid points as the collocation points, and Lagrange polynomials as trial functions. The integrals involved in the formulation of the problem are calculated by Gauss-Lobatto integration rule, thereby reducing the problem to a mathematical programming one to which existing well-developed algorithms may be applied. The method is easy to implement and yields very accurate results. An illustrative example is included to confirm the convergence of the pseudospectral Legendre method, and a comparison is made with an existing result in the literature. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 701-718 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This article establishes the existence of a trapped-mode solution to a linearized water-wave problem. The fluid occupies a symmetric horizontal channel that is uniform everywhere apart from a confined region which either contains a thin vertical plate spanning the depth of the channel or has indentations in the channel walls; the forces of gravity and surface tension are operative. A trapped mode corresponds to an eigenvalue of the composition of an inverse differential operator and a Neumann-Dirichlet operator for an elliptic boundary-value problem in the fluid domain. The existence of such an eigenvalue is established by extending previous results dealing with the case when surface tension is absent. © 1998 B.G. Teubner Stuttgart-John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 501-517 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper an initial-boundary-value problem in one-space dimension is studied for the Broadwell model extended to a gas mixture undergoing bimolecular reactions. Techniques of semigroup of bounded positive operators in a suitable Banach space are used to prove existence and uniqueness of the solution on bounded time intervals whose length depends on the initial data. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 685-700 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In the present work, the problem of electromagnetic wave propagation in three-dimensional stratified media is studied. The method of decoupling the electric and magnetic fields is implemented, and the spectral approach is adopted, componentwise, to the vector equation involving the electric field. Operational calculus of self-adjoint, positive operators in suitable Hilbert spaces is used to solve the corresponding initial value problems. The spectral families of these operators for the cases of the whole space and of a finite layer are constructed. A discussion on the applicability of the obtained results to physical problems is also included. © 1998 B.G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 757-780 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper we prove under the assumption of small initial data the global existence of a classical solution to the equations in viscoelasticity, associated with a free damping boundary condition. We also show that if we choose the initial data large enough, blow up will occur in finite time. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 797-821 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider the thermoelastic plate system,utt-γΔutt+Δ2u+αΔθ=0,θt-κΔθ-αΔut=0 and we make a comparison between the models in which γ=0 and γ〉0. We conclude that in the first case the plate system is of a parabolic type, while when γ〉0 the corresponding system has a hyperbolic behaviour. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 883-894 
    ISSN: 0170-4214
    Keywords: solitary wave ; stability ; long wave-short wave resonance equations ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This paper concerns the orbital stability for solitary waves of the Long Wave-Short Wave resonance equations. Since the abstract results of Grillakis et al. [7, 8] cannot be applied directly, we can extend the abstract stability theory and use the detailed spectral analysis to obtain the stability of the solitary waves. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1049-1066 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider particle transport in a three-dimensional convex region V, bounded by the regular surface ∂V. We assume that particles are specularly reflected by ∂V and that a source q is assigned on ∂V; more general non-homogeneous boundary conditions are also discussed. The problem is non-linear because the boundary condition is not homogeneous. We prove existence of a unique strict solution and by using the theory of semigroups we derive the explicit expression of such a solution in terms of the boundary source q. In the appendix, we indicate how some properties of affine operators can be used to derive the solution. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1085-1105 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: A phase-field model based on the Coleman-Gurtin heat flux law is considered. The resulting system of non-linear parabolic equations, associated with a set of initial and Neumann boundary conditions, is studied. Existence, uniqueness, and regularity results are proved. An asymptotic analysis is also carried out, in the case where the coefficient of the interfacial energy term tends to 0. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1115-1148 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We apply the Child-Langmuir asymptotics of the Vlasov-Poisson system to the case of a bipolar diode, i.e. a vacuum diode where two species of particles of opposite electric charge are flowing. This leads to a simplified model which, if at least one of the two injected currents is not too large, has a unique solution. Moreover, in that case, the currents flowing inside the diode are limited by the so-called bipolar Child-Langmuir currents. In the case of large currents, other solutions may appear, and the formation of virtual electrodes may occur inside the diode. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1107-1113 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper we consider the Cauchy problem for the equation∂u/∂t + u ∂u/∂x + u/x = 0 for x 〉 0, t ≥ 0, with u(x, 0) = u0-(x) for x 〈 x0, u(x, 0) = u0+(x) for x 〉 x0, u0-(x0) 〉 u0+(x0). Following the ideas of Majda, 1984 and Lax, 1973, we construct, for smooth u0- and u0+, a global shock front weak solution u(x, t) = u-(x, t) for x 〈 φ(t), u(x, t) = u+(x, t) for x 〉 φ(t), where u- and u+ are the strong solutions corresponding (respectively) to u0- and u0+ and the curve t → φ(t) is defined by dφ/dt (t) = 1/2[u-(φ(t), t) + u+(φ(t), t)], t ≥ 0 and φ(0) = x0.© 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1195-1206 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: A variational approach to a non-linear non-local identification problem related to the non-linear transport equation is studied. Introducing a similarity transformation, the problem is formulated as an identification problem for a non-linear differential equation of second order with an additional non-local condition. For the solution of the forward problem stability in H1-norm with respect to the identification parameter is obtained. Using this result the existence of a solution to the identification problem is proved. Some results of computational experiments are given. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1233-1267 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider the plate equation in a polygonal domain with free edges. Its resolution by boundary integral equations is considered with double layer potentials whose variational formulation was given in Reference 25. We approximate its solution (u, (∂u/∂n)) by the Galerkin method with approximated spaces made of piecewise polynomials of order 2 and 1 for, respectively, u and (∂u/∂n). A prewavelet basis of these subspaces is built and equivalences between some Sobolev norms and discrete ones are established in the spirit of References 14, 16, 30 and 31. Further, a compression procedure is presented which reduces the number of nonzero entries of the stiffness matrix from O(N2) to O(N log N), where N is the size of this matrix. We finally show that the compressed stiffness matrices have a condition number uniformly bounded with respect to N and that the compressed Galerkin scheme converges with the same rate than the Galerkin one. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1287-1296 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The relativistic Vlasov-Maxwell-Fokker-Planck system is used in modelling distribution of charged particles in plasma. It consists of a transport equation coupled with the Maxwell system. The diffusion term in the equation models the collisions among particles, whereas the viscosity term signifies the dynamical frictional forces between the particles and the background reservoir. In the case of one space variable and two momentum variables, we prove the existence of a classical solution when the initial density decays fast enough with respect to the momentum variables. The solution which shares this same decay condition along with its first derivatives in the momentum variables is unique. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1415-1439 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider reactive mixtures of dilute polyatomic gases in full vibrational non-equilibrium. The governing equations are derived from the kinetic theory and possesses an entropy. We recast this system of conservation laws into a symmetric conservative form by using entropic variables. Following a formalism developed by the authors in a previous paper, the system is then rewritten into a normal form, that is, in the form of a quasilinear symmetric hyperbolic-parabolic system. Using a result of Vol'pert and Hudjaev, we prove local existence and uniqueness of a bounded smooth solution to the Cauchy problem. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1479-1494 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: Approximate solutions of the non-linear Boltzmann equation, which have the structure of the linear combination of three global Maxwellians with arbitrary hydrodynamical parameters, are considered. Some sufficient conditions which allow the error between the left- and the right-hand sides of the equation tend to zero, and which are calculated either in the mixed metric or in the pure integral metric, are obtained. The class of the distributions, which minimized this error for the arbitrary Knudsen number, is found. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1519-1542 
    ISSN: 0170-4214
    Keywords: non-hyperbolic systems ; two-phase flows ; dispersion terms ; symmetrization ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The paper considers a system of partial differential equations of convection dispersion type, modelling a stratified two-phase fluid flow. Local existence in time is proved for a sufficiently smooth initial data, given in the set of physically admissible states. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1559-1569 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper we study the motion of an elastic conducting wire in a magnetic field. The motion of the conductor induces a current in the wire (Faraday's law) which, in turn produces a force on the wire. We consider the linear equation obtained by linearizing the resulting equations of motion about an equilibrium solution. This is a hyperbolic partial differential equation with a non-local term. We prove existence and uniqueness of a weak solution of an initial-boundary value problem for this equation. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1637-1654 
    ISSN: 0170-4214
    Keywords: generalized Stokes equations ; incompressible flow ; least-squares ; finite element method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper we are concerned with a weighted least-squares finite element method for approximating the solution of boundary value problems for 2-D viscous incompressible flows. We consider the generalized Stokes equations with velocity boundary conditions. Introducing the auxiliary variables (stresses) of the velocity gradients and combining the divergence free condition with some compatibility conditions, we can recast the original second-order problem as a Petrovski-type first-order elliptic system (called velocity-stress-pressure formulation) in six equations and six unknowns together with Riemann-Hilbert-type boundary conditions. A weighted least-squares finite element method is proposed for solving this extended first-order problem. The finite element approximations are defined to be the minimizers of a weighted least-squares functional over the finite element subspaces of the H1 product space. With many advantageous features, the analysis also shows that, under suitable assumptions, the method achieves optimal order of convergence both in the L2-norm and in the H1-norm. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1619-1635 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider the two-parameter non-linear Sturm-Liouville problems. By using the variational method on general level sets, the variational eigenvalues are obtained. The purpose of this paper is to study the properties of these variational eigenvalues with respect to the parameter of general level sets. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 187-226 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We study the limit behaviour of solution of Poisson's equation in a class of thin two-dimensional domains, both simply connected or single-hollowed, as its thickness becomes very small. The method is based on a transformation of the original problem into another posed on a fixed domain, obtention of a priori estimates and convergence results when thickness parameter tends to zero. As an important application of abstract results we obtain the limit expressions for functions appearing in elastic beam theories as torsion and warping functions. In this way, we provide a mathematical justification and a correct definition of torsion, warping and Timoshenko functions and constants that should be used in the open and closed thin-walled elastic beam theories. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 269-279 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The generalized Möbius function and Möbius inversion formula are applied to a multiplicative semigroup. A general mathematical method based on this Möbius inversion is presented to solve inversion problems of expansions with unequally weighted terms. By this method, all the inverse lattice problems in physics can be solved concisely. The solutions of four inverse lattice problems: the Fibonacci structure, the square lattice structure, the bcc and the hcp lattice structures are given. These are difficult to be solved by other methods. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 361-374 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We use the eigenfunction expansion of Green's function of Dirichlet problems to obtain sampling theorems. The analytic properties of the sampled integral transforms as well as the uniform convergence of the sampling series are proved without any restrictions on the integral transforms. We obtain a one- and multi-dimensional versions of sampling theorems. In both cases the sampling series are written in terms of Lagrange-type interpolation expansions. Some examples and the truncation error as well as the stability of the obtained sampling expansions are discussed at the end of the paper. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 393-416 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider a dynamical von Kármán system in the presence of thermal effects. Our model includes the possibility of a rotational inertia term in the system. We show that the total energy of the solution of such system decays exponentially as t→+∞. The decay rates we obtain are uniform on bounded sets of the energy space. The main ingredients of our method of proof are suitable properties of a decoupled system, the energy method and the compactness of the nonlinear map associated to the von Kármán system. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 479-488 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This short article discusses the spectrum of the Neumann Laplacian in the infinite domain Ω⊂∝n, n ≥2 created by inserting a compact obstacle P into the uniform cylinder Ω0 =(-∞, ∞)×Ω′. The main result is the existence of at least one embedded eigenvalue when P is an (n -2)-dimensional surface whose unit normal is parallel to Ω′ at each point of P . The special case when P is symmetric about {0}×Ω′ is also treated. It is shown that there is at least one symmetric eigenvector and, when P is sufficiently long, at least one antisymmetric eigenvector. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 551-564 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We prove the existence of solutions to the three-dimensional elastoplastic problem with Hencky's law and Neumann boundary conditions by elliptic regularization and the penalty method, both for the case of a smooth boundary and of an interior two dimensional crack. It is shown, in particular, that the variational solution satisfies all boundary conditions. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
    Type of Medium: Electronic Resource
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  • 96
    Electronic Resource
    Electronic Resource
    Chichester, West Sussex : Wiley-Blackwell
    Mathematical Methods in the Applied Sciences 21 (1998), S. 251-268 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The propagation of Hölder regularity of the solutions to the 3D Euler equations is discussed. Our method is a special semi-linearization of the vorticity equation combined with the classical Schauder interior estimates. © 1998 by B.G. Teubner Stuttgart-John Wiley & Sons Ltd.
    Type of Medium: Electronic Resource
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  • 97
    Electronic Resource
    Electronic Resource
    Chichester, West Sussex : Wiley-Blackwell
    Mathematical Methods in the Applied Sciences 21 (1998), S. 433-461 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This paper is concerned with the solution of Maxwell equations in the modelling of the scattering of a time-harmonic electromagnetic wave by an obstacle located in a two-layered medium. The use of the Silver-Müller radiation condition in each layer is shown to provide a well-posed scattering problem. The analysis is based on the study of the Green tensor, which allows to relate the radiation condition to an integral representation formula. The analyticity properties of the scattering problem with respect to the frequency are then investigated. This gives rise to a limiting absorption principle and furnishes a characterization of the resonances. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 98
    Electronic Resource
    Electronic Resource
    Chichester, West Sussex : Wiley-Blackwell
    Mathematical Methods in the Applied Sciences 21 (1998), S. 489-499 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We apply our recently developed distributional technique [2, 3] to study time-domain asymptotics. This enables us to present a rigorous mathematical discussion and extensions of the results given by Chapman [1] and subsequent workers in this field. The present analysis is facilitated by defining functions which are distributionally small at infinity. We find that one of the advantages of using this technique is that multidimensional extensions can be derived very easily. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    Chichester, West Sussex : Wiley-Blackwell
    Mathematical Methods in the Applied Sciences 21 (1998), S. 519-549 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This paper is concerned with a specific finite element strategy for solving elliptic boundary value problems in domains with corners and edges. First, the anisotropic singular behaviour of the solution is described. Then the finite element method with anisotropic, graded meshes and piecewise linear shape functions is investigated for such problems; the schemes exhibit optimal convergence rates with decreasing mesh size. For the proof, new local interpolation error estimates for functions from anisotropically weighted spaces are derived. Finally, a numerical experiment is described, that shows a good agreement of the calculated approximation orders with the theoretically predicted ones. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    Chichester, West Sussex : Wiley-Blackwell
    Mathematical Methods in the Applied Sciences 21 (1998), S. 605-617 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This paper presents a general method of analysis for investigating the whirl stability of a rotor-bearing system whose appendage is flexibly attached to the spinning shaft. Sufficient conditions of asymptotic stability involving system different parameters are derived based on Liapunov's theory. An inclusive analysis of the effect of the combined flexibilities of the elastic attachment of the appendage to the shaft and the two end bearings coupled with the other various parameters of the system on the dynamic stability is presented. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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