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  • 1
    ISSN: 1432-0428
    Keywords: Keywords Diabetic cardiovascular autonomic neuropathy ; MIBG scintigraphy ; sympathetic denervation ; autonomic function tests ; glycaemic control.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Diabetic cardiovascular autonomic neuropathy (CAN) has been directly characterized by reduced or absent myocardial [123I]metaiodobenzylguanidine (MIBG) uptake, but there is no information available on the relationship between the myocardial adrenergic innervation defects and long-term glycaemic control. In a prospective study over a mean of 4 years we examined myocardial sympathetic innervation in 12 Type 1 (insulin-dependent) diabetic patients using MIBG scintigraphy (absolute and relative global MIBG uptake at 2 h p. i.) in conjunction with cardiovascular autonomic function tests, QTc interval, and QT dispersion. Six healthy non-diabetic subjects served as controls for the MIBG scintigraphy at baseline. HbA1c was measured twice a year. One patient, in whom MIBG accumulation was reduced maximally, died during follow up. Among the remaining patients 5 had good or borderline glycaemic control (mean HbA1c 〈 7.6 %; Group 1), whereas 6 patients were poorly controlled (mean HbA1c L 7.6 %; Group 2). Absolute global MIBG uptake increased from baseline to follow-up by 260 (−190–540) [median (range) ] cpm/g in Group 1 and decreased by −150 (−450–224) cpm/g in Group 2 (p 〈 0.05 vs Group 1). Relative global MIBG uptake decreased by −1.7 (−3.4–9.4) % in Group 1 and by −4.7 (−17.4–1.3) % in Group 2 (p 〈 0.05 vs Group 1). No differences between the groups were noted for the changes in the automatic function tests, QTc interval, and QT dispersion. In conclusion, long-term poor glycaemic control constitutes an essential determinant in the progression of left ventricular adrenergic dysinnervation which may be prevented by near-normoglycaemia. Evaluation of susceptibility to metabolic intervention may be superior when CAN is characterized directly by MIBG scintigraphy rather than by indirect autonomic function testing. [Diabetologia (1998) 41: 443–451]
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Key words Episodic memory ; Paired word association ; fMRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The investigation of memory function using functional magnetic resonance imaging (fMRI) is an expanding field of research. The aim of this study was to demonstrate brain-activity patterns related to a word-pair association task employing a whole-brain EPI sequence. Six right-handed, healthy male volunteers (mean age: 27.5 years) took part in the study. fMRI was performed at a field strength of 1.5 Tesla with 26–32 slices parallel to the AC-PC line, depending on individual brain size. Distributed brain regions were activated in episodic encoding and retrieval with similarities, but also (distinct) differences in activation patterns. Bilateral prefrontal cortical areas were involved when comparing encoding as well as retrieval to the reference condition (nonsense words). Furthermore, activation was observed in cerebellar areas during encoding, and activation in bilateral parietal areas (precuneus and inferior parietal cortex) was differentially more pronounced during retrieval. The activation of left dorsomedial thalamus during retrieval of high imagery-content word-pair associates may point to the role of this structure in episodic retrieval. The direct cognitive subtraction of encoding minus retrieval yielded a differentially larger left prefrontal activation. There was a differentially higher right prefrontal activation during retrieval than during encoding, underlining the proposed right/left asymmetry for episodic memory processes.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The involvement of distributed brain regions in declarative memory has been hypothesized based on studies with verbal memory tasks. To characterize episodic declarative memory function further, 14 right-handed volunteers performed a visual verbal learning task using paired word associates. The volunteers underwent positron emission tomography. 15O-butanol was used as a tracer of regional cerebral blood flow (rCBF). Inter-regional functional interactions were assessed based on within-task, across-subject inter-regional rCBF correlations. Anatomical connections between brain areas were based on known anatomy. Structural equation modelling was used to calculate the path coefficients representing the magnitudes of the functional influences of each area on the ones to which it is connected by anatomical pathways. The encoding and the retrieval network elicit similarities in a general manner but also differences. Strong functional linkages involving visual integration areas, parahippocampal regions, left precuneus and cingulate gyrus were found in both encoding and retrieval; the functional linkages between posterior regions and prefrontal regions were more closely linked during encoding, whereas functional linkages between the left parahippocampal region and posterior cingulate as well as extrastriate areas and posterior cingulate gyrus were stronger during retrieval. In conclusion, these findings support the idea of a global bihemispheric, asymmetric encoding/retrieval network subserving episodic declarative memory. Our results further underline the role of the precuneus in episodic memory, not only during retrieval but also during encoding.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nuclear medicine 24 (1997), S. 1514-1521 
    ISSN: 1619-7089
    Keywords: Key words: Residence times ; Radiation dosimetry ; Excel ; MIRDOSE3Introduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. We developed a program which aims to facilitate the calculation of radiation doses to single organs and the whole body. IMEDOSE uses Excel to include calculations, graphical displays, and interactions with the user in a single general-purpose PC software tool. To start the procedure the input data are copied into a spreadsheet. They must represent percentage uptake values of several organs derived from measurements in animals or humans. To extrapolate these data up to seven half-lives of the radionuclide, fitting to one or two exponentional functions is included and can be checked by the user. By means of the approximate time-activity information the cumulated activity or residence times are calculated. Finally these data are combined with the absorbed fraction doses (S-values) given by MIRD pamphlet No. 11 to yield radiation doses, the effective dose equivalent and the effective dose. These results are presented in a final table. Interactions are realized with push-buttons and drop-down menus. Calculations use the Visual Basic tool of Excel. In order to test our program, biodistribution data of fluorine-18 fluorodeoxyglucose were taken from the literature (Meija et al., J Nucl Med 1991; 32:699–706). For a 70-kg adult the resulting radiation doses of all target organs listed in MIRD 11 were different from the ICRP 53 values by 1%±18% on the average. When the residence times were introduced into MIRDOSE3 (Stabin, J Nucl Med 1996; 37:538–546) the mean difference between our results and those of MIRDOSE3 was –3%±6%. Both outcomes indicate the validity of the present approach.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1619-7089
    Keywords: Key words: l-3-[I-123]iodo-α-methyltyrosine ; Dosimetry ; Brain tumours ; Amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The synthetic amino acid l-3-[123I]iodo-α-methyltyrosine (IMT) is currently under clinical evaluation as a single-photon emission tomography (SPET) tracer of amino acid uptake in brain tumours. So far, dosimetric data in respect of IMT are not available. Therefore we investigated the whole-body distribution of IMT in six patients with cerebral gliomas and the radiation doses were estimated. Whole-body scans were acquired at 1.5, 3 and 5 h after i.v. injection of 370–550 MBq IMT. The bladder was voided prior to each scan and the radioactivity excreted in the urine was measured. Based on the MIRD-11 method and the updated MIRDOSE3, the mean absorbed doses for various organs and the effective dose were calculated from geometric means of the anterior and posterior whole-body scans using seven source organs and the residence time. IMT was predominantly excreted by the kidneys (52.8%±11.5% at 1.5 h p.i., 63.0%±15.7% at 3 h p.i. and 74.6%±9.8% at 5 h p.i.). No organ system other than the urinary tract showed significant retention of the tracer. Early whole-body scans revealed slightly increased tracer uptake in the liver and in the bowel. Highest absorbed doses were found for the urinary bladder wall (0.047 mGy/MBq), the kidneys (0.010 mGy/MBq), the lower large intestinal wall (0.011 mGy/MBq) and the upper large intestinal wall (0.008 mGy/MBq). The effective dose according to ICRP 60 was estimated to be 0.0073 mSv/MBq for adults. This leads to an effective dose of 3.65 mSv in a typical brain SPET study using 500 MBq IMT. The MIRDOSE3 scheme yielded similar results. Thus, in spite of the relatively high tracer dose required for optimal brain scanning, radiation exposure in SPET studies with IMT is in the normal range of routine nuclear medicine investigations.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1619-7089
    Keywords: Oxygen-15 labelled butanol ; Pharmacokinetics ; Dosimetry ; Cerebral blood flow ; Positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In this positron emission tomography (PET) study in humans we determined the pharmacokinetics and radiation dose of oxygen-15 labelled butanol, a recently introduced tracer for regional cerebral blood flow (rCBF). This report includes a description of the automated preparation of 150-butanol which allows repetitive activation studies, each 15 min apart. Dynamic rCBF studies were extended by prolonged measurements up to 15 min after injection over different organs such as brain, liver, kidneys and bladder. All measurements were done with a whole-body PET camera PC4096-15WB. Based on the pharmacokinetic data in 13 subjects the radiation doses to single organs were calculated according to MIRD pamphlet No. 11 and the effective dose defined by ICRP 60 as an indicator of radiation dose to the total body. The liver received the highest radiation dose of about 2.2 mGy per 1500 MBq of injected 15O-butanol, which is the typical amount of administered tracer in one rCBF measurement. The dose to the kidneys was 1.6 mGy, to the stomach 0.8 mGy, and to the brain 0.16 mGy. The effective dose was 0.54 mGy, which was similar to that of H2 15O, but lower than the effective dose from C15O2 in amounts typically applied in human rCBF studies.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1619-7089
    Keywords: Key words: Cholinergic system ; Muscarinic receptors ; Epilepsy ; Emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Animal experiments and preliminary results in humans have indicated alterations of hippocampal muscarinic acetylcholine receptors (mAChR) in temporal lobe epilepsy. Patients with temporal lobe epilepsy often present with a reduction in hippocampal volume. The aim of this study was to investigate the influence of hippocampal atrophy on the quantification of mAChR with single photon emission tomography (SPET) in patients with temporal lobe epilepsy. Cerebral uptake of the muscarinic cholinergic antagonist [123I]4-iododexetimide (IDex) was investigated by SPET in patients suffering from temporal lobe epilepsy of unilateral (n=6) or predominantly unilateral (n=1) onset. Regions of interest were drawn on co-registered magnetic resonance images. Hippocampal volume was determined in these regions and was used to correct the SPET results for partial volume effects. A ratio of hippocampal IDex binding on the affected side to that on the unaffected side was used to detect changes in muscarinic cholinergic receptor density. Before partial volume correction a decrease in hippocampal IDex binding on the focus side was found in each patient. After partial volume no convincing differences remained. Our results indicate that the reduction in hippocampal IDex binding in patients with epilepsy is due to a decrease in hippocampal volume rather than to a decrease in receptor concentration.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1619-7089
    Keywords: Key words: Breast cancer ; Fluorine-18 fluorodeoxyglucose ; Positron emission tomography ; Tumour-to-non-tumour ratio ; Contrast parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) has proven useful in the differentiation of various tumour entities, including breast cancer. In patients with primary breast cancer we performed a 3-h imaging protocol to examine possible improvements in tumour detectability and image contrast. Twenty-nine patients with primary breast cancer with a diameter of ≥2 cm that was demonstrated to be malignant by biopsy or surgery were injected with 370–740 MBq 18F-FDG and scanned in the prone position. Data were acquired 0–40 min, 1.5 h and 3.0 h after injection. After correction for measured attenuation, decay and scatter and iterative reconstruction, standardised uptake values (SUVs) and tumour-to-non-tumour and tumour-to-organ ratios were calculated. Visual analysis was performed using transverse, sagittal and coronal slices as well as 3D reprojection images. Tumour-to-non-tumour and tumour-to-organ ratios were significantly higher for the 3-h images than for the 1.5-h images. SUVs did not increase to the same extent. Lesion detectability was 83% in 1.5-h images compared to 93% in 3-h images. We conclude that tumour contrast in breast cancer is improved by starting the PET acquisition at 3 h p.i. rather than at 1.5 h p.i.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Positronen-Emissions-Tomographie (PET) ; Neurologie ; Neurochirurgie ; Psychiatrie ; Key words Positron emission tomography ; Neurology ; Neurosurgery ; Psychiatry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary To date, positron emission tomography (PET) is the most powerful method for the in-vivo investigation of human brain metabolism. Besides extensive application of this technology in the neurosciences, PET is also being increasingly used as a clinical tool. However, despite its acceptance in clinical practice, a major obstacle is its high costs. The present article reviews the literature on the clinical use of PET in neurology, neurosurgery, and psychiatry in order to substantiate the clinical indications for PET in these specialties as established by an interdisciplinary conference.
    Notes: Zusammenfassung Die Positronen-Emissions-Tomographie (PET) ist das derzeit leistungsfähigste Verfahren zur In-vivo-Untersuchung des zerebralen Stoffwechsels. Neben einem breitgefächerten Einsatz von PET in der neuromedizinischen Forschung findet die PET zunehmend auch Eingang in die klinische Diagnostik. Dieser Entwicklung entgegen stehen die relativ hohen Kosten, die mit diesem Verfahren verbunden sind. Die vorliegende Arbeit begründet die, in einer interdisziplinären Konferenz erarbeiteten Konsensusindikationen für den klinischen Einsatz der PET in der Neurologie, Neurochirurgie und Psychiatrie durch Aufarbeitung der einschlägigen Literatur.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1433-0563
    Keywords: Key words Positron emission tomography • Fluorodeoxyglucose • Testicular cancer • Lymph node metastases ; Schlüsselwörter Positronenemissionstomographie • Fluordeoxyglukose • Hodentumoren • Lymphknotenmetastasen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Das Ziel dieser 1991 begonnenen prospektiven Studie war, die Bedeutung der Positronenemissionstomographie mit 18FDG bei der Diagnostik der Lymphknotenmetastasen von Hodentumoren zu untersuchen, da zu diesem Zeitpunkt keine Daten bezüglich dieser Fragestellung zur Verfügung standen. Es wird über 54 Patienten berichtet (27 Patienten mit reinem Seminom, 27 Patienten mit nichtseminomatösen Tumoren), bei denen die 18FDG-PET-Resultate mit den Befunden der abdominellen Computertomographie, den Werten für die Tumormarker (AFP, β -HCG) sowie den histopathologischen Befunden nach primärer oder post-chemotherapeutischer retroperitonealer Lymphknotendissektion verglichen wurden. Bei reinen Seminomen im klinischen Stadium I nach der Lugano-Klassifikation (N = 21) waren die 18FDG-PET-Ergebnisse identisch mit denen der Computertomographie, so daß das Verfahren bei dieser Patientengruppe keine zusätzlichen Informationen bringt. Bei Patienten mit nichtseminomatösen Tumoren im Stadium I (N = 7) wurden bei 4 Patienten die vorliegenden Mikrometastasen durch die PET nicht detektiert, bei 1/7 Patienten hat die PET-Messung einen suspekten Herd ergeben, es fanden sich 2 Mikrometastasen in einem zusätzlich entzündlich veränderten Lymphknoten. In 1/7 Fall hat die 18FDG-PET eindeutig Metastasen detektiert (Tumormarker und Computertomogramm waren unauffällig). Bei den reinen Seminomen der Stadien II B und II C (N = 6) hat 18FDG-PET nach Chemotherapie das tumorfreie Lymphknotendissektat (pN0) von den 4 operierten Patienten 3 mal richtig präoperativ erkannt und im vierten Fall einer persistierenden großen Raumforderung die benigne Eigenschaft der Läsion (Ganglioneurom) identifiziert. Computertomographisch wurde dieser Befund als maligne (falsch-positiv) eingestuft, und bei 2/4 Patienten konnten computertomographisch residuale Lymphknoten nach Chemotherapie nicht eindeutig klassifiziert werden. Bei 20 Patienten mit nicht-seminomatösen Tumoren (Stadien II und III) konnte mit 18FDG-PET der Einfluß der Chemotherapie durch Aktivitätsminderung in prätherapeutisch hypermetabolen Herden (Normalisierung bis auf Hintergrundniveau) dargestellt werden. Es gibt eine einzige maligne Ausprägung der Hodentumoren, das reife Teratom, welche keine vermehrte 18FDG-Aufnahme zeigt. Bei computertomographisch erkennbaren, in der PET aber unauffällig dargestellten Läsionen sind differentialdiagnostisch reifes Teratom, Narbengewebe und/oder Nekrose bzw. seltene andere Tumorarten ohne gesteigerten Glukosestoffwechsel in Erwägung zu ziehen, aber eindeutige Unterschiede der Traceraufnahme zur weiteren Differenzierung wurden nicht beobachtet. In 1/20 Fall lag in der PET postchemotherapeutisch ein hypermetaboler Herd, fälschlich als maligne eingestuft, vor, der entsprechende Lymphknoten zeigte histopathologisch entzündliche Veränderungen. 18FDG-PET ist nicht als Routine-Untersuchungsverfahren bei Hodentumoren anzusehen. Die sinnvollste Anwendung ist bei der Bewertung von post-chemotherapeutischen Residualtumoren gegeben, um eine Entscheidungshilfe bei der Indikationsstellung zur RLA/weiteren Chemotherapie zu sein, jedoch ist die RLA zum Staging der Lymphknoten durch den Einsatz der 18FDG-PET nicht zu ersetzen.
    Notes: Summary In 1991, this prospectively designed study was started to assess the potentials of positron emission tomography with 18FDG in the diagnostic workup for the detection of lymph node metastases in testicular cancer, since there were no data available concerning this subject at this time. In 54 patients (27 patients with pure seminoma, 27 patients with non-seminomatous tumors) 18FDG-PET results were compared with the findings obtained with abdominal computed tomography, serum level of tumor markers (AFP, β -HCG), and the histopathological findings after primary or post-chemotherapy retroperitoneal lymph node dissection. In 21 patients with pure seminoma (clinical stage I according to the Lugano classification) 18FDG-PET results were identical with those of the abdominal computed tomography, so PET does not add relevant informations in this group of patients. In 7 patients presenting with non-seminomatous testicular cancer (stage I), PET was not able to detect the existing micrometastases in 4 patients. In 1/7 case PET examination showed a suspicious focal lesion, this lymph node had 2 micrometastases within inflammatory changes. In 1/7 patient 18FDG-PET definitely revealed metastatic lesions, while the CT scans where judged to be unobtrusive and tumor marker levels were within the normal range. In the 4 patients with pure seminomas stage II B and II C (N = 6), that have undergone retroperitoneal lymph node dissection following chemotherapy, 18FDG-PET correctly predicted absence of tumor in 3 out of these 4, and in 1/4 patient the benign nature of a persistent large tumor after two cycles of polychemotherapy was correctly identified wich eventually turned out to be a ganglioneuroma. This lesion falsely was classified as malignant tumor with abdominal computed tomography, and in 2/4 patients post-chemotherapy residual retroperitoneal lesions in the CT scans could not be assessed exactly whether or not malignant tumor was present. In 20 patients presenting with non-seminomatous testicular cancer (stage II and III) 18FDG-PET was able to demonstrate therapeutic effects of chemotherapy by showing decreasing tracer activity in those regions, that had hypermetabolic foci prior to chemotherapy. It became evident in testicular cancer that there is a single entity which is not characterized by increased glucose metabolism, the mature teratoma. In lesions detected by abdominal computed tomography which do not present increased 18FDG uptake, mature teratoma as well as scar/necrosis or rare other tumors with normal glucose metabolism can be supposed, but additional characteristics based on different 18FDG uptake were not observed. In 1/20 case post-chemotherapy PET scan detected a hypermetabolic lesion, which was suspicious for metastatic spread, but in the histopathological examination this lesion was identified as inflammatory tissue reaction. Based on the data reported here in 18FDG-PET cannot be considered a standard diagnostic tool in the staging examinations in testicular cancer. It is of clinical relevance in patients who present residual tumor after chemotherapy. In this situation 18FDG-PET is helpful in deciding whether or not a residual mass post-chemotherapy contains active tumor. 18FDG-PET can not replace retroperitoneal lymph node dissection for staging purposes.
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