PubMed Health⌕ Search

Biomedical subjects

T Kuwert

Publications and source records attributed to T Kuwert.

At least 55 records · Page 3Linked to original sources
PubMed1998

Measurement of temporal asymmetries of glucose consumption using linear profiles: reproducibility and comparison with visual analysis.

AIM: One approach to regionally analyze temporal glucose consumption consists in drawing linear profiles over the maximal values measured in the temporal cortical ribbon. The aim of our study was to test the reproducibility of this method and to compare its diagnostic performance to that of visual analysis in patients with complex partial seizures (CPS). METHODS: Regional cerebral glucose consumption (rCMRGIc) was measured interictally in 25 CPS patients and 10 controls using F-18-deoxyglucose and the positron emission tomography (PET) camera ECAT EXACT 47. The PET scans were visually analyzed for the occurrence of unilateral temporal hypometabolism. Furthermore, rCMRGIc was quantified on six contiguous coronal planes by manually tracing maximal values of temporal glucose consumption, thus creating line profiles of temporal glucose consumption for each side. Indices of asymmetry (ASY) were then calculated from these line profiles in four temporal regions and compared to the corresponding 95% confidence intervals of the control data. All analyses were performed by two observers independently from each other and without knowledge of the clinical findings. RESULTS: The agreement between the two observers with regard to focus lateralization was 96% (kappa = 0.93) on visual analysis and 100% (kappa = 1) on quantitative analysis. There was an excellent agreement with regard to focus lateralization between visual and quantitative evaluation (kappa = 0.8). CONCLUSION: Quantitation of local temporal rCMRGIc by using linear profile analysis is highly reproducible; for the lateralization of epileptogenic foci, however, this method does not possess significant advantages over the visual evaluation of the scans.

Adult↗
PubMed1998

Costs of F-18-FDG PET: experience with a satellite concept.

AIM: One of the main arguments against the acceptance and introduction of FDG PET as a regular benefit in the statutory Medical Insurance system in Germany are its (alleged) high costs. The aim of the present study has been to determine empirically over a period of twelve months the costs of FDG PET, making use of a satellite concept. METHODS: Documentation on performance and consumption data has been assembled for purposes of cost analysis. After analysis these data provided the basis for an assessment of the costs. In view of the high proportion of fixed overheads and strong fluctuations in consumption values, it was not possible to allocate reliably in an individual FDG PET investigation the various types of costs to individual causes. A monthly cost assessment procedure was therefore adopted. For this purpose data were recorded in the department for Nuclear Medicine, while the statistical assessment of the consumption data and analysis of the costs were undertaken in the Institute of Industrial and Hospital Management. RESULTS: Over the twelve month observation period (November 1995 to October 1996, 177 working days) 433 patients were included in the study: 244 with brain diseases 37 cardiac patients, 130 whole body studies and 22 combined studies (brain and whole body scans). The non volume based costs, maintenance charges and depreciation accounted for the highest proportion of the total costs (48%). The FDG-related costs accounted for 41% of the total costs, while the personnel costs amounted to 11% and the film costs to only 0.45%. The total costs incurred amounted to DM 1,205,050. CONCLUSION: These data represent a first empirical cost analysis for FDG PET based on a satellite concept and form a starting point for a cost/benefit analysis of this procedure.

Brain↗
PubMed1998

PET and SPECT in medically non-refractory complex partial seizures. Temporal asymmetries of glucose consumption, benzodiazepine receptor density, and blood flow.

AIM: In contrast to medically refractory complex partial seizures (CPS), only limited knowledge exists on cerebral perfusion and metabolism in medically non-refractory CPS. The aim of this study was to investigate the frequency of temporal asymmetries in regional cerebral glucose consumption (rCMRGlc), regional cerebral blood flow (rCBF), and regional cerebral benzodiazepine receptor density (BRD) in this group of patients. METHODS: The study included 49 patients with medically non-refractory cryptogenic CPS (age: 36.0 +/- 16.1 years). rCMRGlc was studied with F-18-FDG-PET (FDG), rCBF with Tc-99m-ECD-SPECT (ECD), and BRD with l-123-iomazenil-SPECT (IMZ). All studies were performed interictally and within four weeks in each patient. Duration of epilepsy ranged from 0.1 to 42 years (median 4.0 years). SPECT was performed with the triple-headed SPECT camera Multispect 3, PET with the PET camera ECAT EXACT 47. Using linear profiles, glucose consumption, as well as uptake of ECD and IMZ, were measured in four temporal regions of interest (ROIs), and asymmetry indices were calculated (ASY). The results were compared to 95% confidence intervals determined in control subjects. RESULTS: Thirty-five of the 49 (71%) patients had at least one significantly elevated ASY; temporal rCMRGlc was asymmetrical in 41% of the patients, temporal BRD in 29%, and temporal rCBF in 24%. One patient had an asymmetry of all three variables, two of temporal rCMRGlc and BRD, three of temporal rCMRGlc and rCBF, and another four of rCBF and BRD. Fourteen patients had an isolated temporal asymmetry in rCMRGlc, seven in BRD, and four in rCBF. A discrepancy in lateralization between the three modalities was not observed. CONCLUSION: The majority of patients with medically non-refractory CPS have focal abnormalities of blood flow and metabolism in their temporal lobe. In this group of patients, FDG-PET demonstrates abnormalities with the highest frequency of the three modalities studied, followed by IMZ-SPECT, and ECD-SPECT.

Adolescent↗
PubMed1997

Non-invasive grading of primary brain tumours: results of a comparative study between SPET with 123I-alpha-methyl tyrosine and PET with 18F-deoxyglucose.

Use of iodine-123-alpha-methyl tyrosine (123I-IMT) allows investigation of the amino acid transport rate in gliomas. It was the aim of this study to compare the value of measurement of glucose metabolism with that of measurement of 123I-IMT uptake for the non-invasive grading of brain tumours. The study population comprised 23 patients with histopathologically proven primary brain tumours; 14 had high-grade gliomas, and nine low-grade brain neoplasms. Glucose metabolism was studied using an ECAT EXACT 47 positron emission tomography (PET) camera and fluorine-18 fluorodeoxyglucose (18F-FDG); 123I-IMT uptake was measured with the triple-headed single-photon emission tomography (SPET) camera, MULTISPECT 3. 18F-FDG and 123I-IMT uptake was quantified as ratios between the uptake by the tumour and contralateral regions of reference. Glucose metabolism and amino acid uptake of the brain tumours correlated significantly (r=0.71, P <0.001). Assuming discrimination thresholds between high-grade and low-grade tumours of 0.8 for 18F-FDG uptake and 1.8 for 123I-IMT uptake, the accuracy values of 18F-FDG PET and 123I-IMT SPET for differentiating between high-grade and low-grade tumours were 21/23 (91%) and 19/23 (83%), respectively. The difference in diagnostic performance was not significant on receiver operating characteristic analysis (P >0.4). It is concluded that there is no major difference between the PET investigation of glucose metabolism and the less expensive SPET measurement of amino acid uptake in terms of their accuracy in evaluating the malignancy grade of primary brain tumours. This encourages the performance of further studies to analyse the potential impact of 123I-IMT SPET on the therapeutic management of patients with brain tumours.

Adult↗
PubMed1997

Survival of differentiated thyroid carcinoma studied in 500 patients.

PURPOSE: To analyze the factors that influence survival of patients with differentiated thyroid carcinoma treated by surgical thyroidectomy, radioactive iodine, and early surgical reintervention with compartment-oriented lymphadenectomy in the case of locoregional recurrence. METHODS: The survival of 500 patients with differentiated thyroid carcinoma was analyzed retrospectively with regard to mortality and survival rate (Kaplan-Meier). A total of 301 patients had papillary and 199 follicular thyroid carcinoma. The mean age of the 380 women and 120 men was 46.8 +/- 16.4 years at presentation. All patients were treated by surgical thyroidectomy, high-dose radioactive iodine, and early surgical reintervention with compartment-oriented lymphadenectomy in cases of locoregional recurrence, without routine adjuvant external radiotherapy of the neck. Patients were monitored up to 23 years, with a median follow-up time of 5.6 years. RESULTS: Twenty-nine of 500 patients died, 19 of thyroid cancer. The corrected overall 5-year survival rate (Kaplan-Meier) was 0.92. Among patients with tumor stage pT1-3NO-1MO (low risk), none died of thyroid carcinoma (5-year survival rate, 0.97); in patients with tumor stage pT4 and/or M1 (high risk), the 5-year survival rate was 0.83. The cause of death was locoregional recurrence in eight and metastatic disease in 11. Using multivariate analysis, risk factors that significantly influence survival were local invasion (pT4), metastatic disease (M1), and age. CONCLUSION: In differentiated thyroid carcinoma, the use of total surgical thyroidectomy followed by high-dose radioiodine therapy and early surgical reintervention in case of locoregional recurrence yields high survival rates, even without adjuvant external radiotherapy of the neck.

Adenocarcinoma, Follicular↗
PubMed1997

3-[123I]iodo-alpha-methyltyrosine and [methyl-11C]-L-methionine uptake in cerebral gliomas: a comparative study using SPECT and PET.

UNLABELLED: This study compares the uptake of the nonmetabolizable amino acid analog 3-[123I]iodo-alpha-methyltyrosine (IMT) and of [methyl-11C]-L-methionine (MET) in cerebral gliomas. METHODS: In 14 patients with cerebral gliomas, IMT uptake was measured using SPECT (10 dynamic, 4 static SPECT acquisitions) and, on the same day, MET uptake by dynamic PET. The IMT and MET data were compared with respect to tracer kinetics, tumor to brain ratios (T/B) and tumor size after converting the resolution of the PET scans to that of the SPECT scans (14 mm FWHM). RESULTS: All gliomas showed increased uptake of both tracers in relation to normal brain tissue. Visual comparison of the scans yielded no differences in tumor size and shape with both methods. IMT showed a maximal tracer uptake in brain and in tumors at about 15 min postinjection which was followed by a washout of 45.0% +/- 13.5% in gliomas (mean +/- s.d., p < 0.001, n = 10) and 35.3% +/- 5.4% in normal brain (p < 0.001, n = 10) at 60 min postinjection. MET concentration in tumor tissue or brain tissue between 15 and 60 min remained constant. T/B ratios of IMT SPECT and MET PET showed a significant correlation at 15 min postinjection (r = 0.69, n = 10, p = 0.03), a low correlation for the mean values of the scans from 15-60 min postinjection (r = 0.54, n = 14, p = 0.05) and no correlation at 60 min postinjection (r = 0.09, n = 10, n.s.). CONCLUSION: IMT and MET uptake in gliomas is similar in the early, transport dominated phase. There are some differences in tumor to brain ratios between both tracers within the first hour postinjection that are mainly caused by variable washout of IMT. Imaging of tumor extent with IMT SPECT is comparable to MET PET. Thus, amino acid SPECT using IMT is a promising tool to evaluate the biological activity and intracerebral infiltration of gliomas.

Adult↗
PubMed1997

Frontal sinus mucocele mimicking a metastasis of papillary thyroid carcinoma.

Radioiodine scans are highly specific for detecting metastases of well-differentiated thyroid carcinomas. However, false-positive 131I whole-body scans may occur as illustrated in the following case report. In a 53-yr-old patient, abnormal 131I uptake was found in the right frontal skull 4 wk after total thyroidectomy and radioiodine therapy for papillary thyroid cancer. Bone scans and planar x-rays of the skull were unremarkable and the serum thyroglobulin level was within normal limits. X-ray CT revealed a small nodule in the right frontal sinus corresponding to the pathological focus of 131I uptake. Surgical removal and histopathological examination of this lesion yielded a mucocele, a slow-growing lesion of the paranasal sinuses accumulating mucous material. The postoperative 131I scan was unremarkable. The possibility of a false-positive finding on radioiodine scans should be considered, particularly when the serum thyroglobulin level is not elevated.

Carcinoma, Papillary↗
PubMed1997

Iodine-123-alpha-methyl tyrosine in gliomas: correlation with cellular density and proliferative activity.

UNLABELLED: Amino acid transport rate in gliomas can be assessed using SPECT and the amino acid L-123I-alpha-methyl tyrosine (IMT). This study attempted to correlate the uptake of IMT by gliomas with the proliferative activity and cellular density of these neoplasms. METHODS: The study used 27 patients with gliomas, including 18 patients with high-grade tumors and nine patients with low-grade neoplasms. Amino acid transport rate was determined using IMT and the triple-headed SPECT camera. Proliferative activity was immunohistochemically assessed as the relative number of cells expressing the Ki-67 nuclear antigen; cellular density was evaluated using light microscopy. RESULTS: Relative IMT uptake correlated significantly with the proliferative fraction of tumor cells (r = 0.6, p < 0.001). There was no significant correlation between IMT uptake and cellular density (r = 0.25, p > 0.05). CONCLUSION: The uptake of the SPECT radiopharmaceutical IMT is related to proliferative activity rather than to the cellular density of gliomas.

Astrocytoma↗
PubMed1997

Myocardial perfusion and metabolism after transcoronary ablation of septum hypertrophy (TASH) in hypertrophic obstructive cardiomyopathy.

Outflow obstruction constitutes a major problem in hypertrophic obstructive cardiomyopathy (HOCM) and may be treated by transcoronary injection of ethanol into septal arteries (transcoronary ablation of septum hypertrophy, TASH). We report on myocardial perfusion and glucose metabolism in a 50 year old man in whom TASH led to a reduction of septal thickness (9 vs. 26 mm), a sustained elimination of the outflow tract obstruction (resting gradient 0 vs. 60 mmHg; post-ES-gradient 10 vs. 145 mmHg) and a substantial clinical improvement (NYHA stage II vs. II-III) without impairment of global ventricular function (left ventricular ejection fraction 0.62 vs. 0.64). After TASH, perfusion and glucose metabolism were assessed by positron emission tomography (PET) using F-18-fluorodeoxyglucose (F-18-FDG) and Tc-99m-MIBI single photon emission tomography (SPECT). TASH results in matched reduction of perfusion and glucose consumption in a circumscribed area fed by the septal branch used for ethanol injection. No remote effects were observed. TASH leads to a sharply delineated septal reduction of perfusion and metabolism with consecutive reduction of septal thickness, a sustained elimination of the outflow tract obstruction, and a substantial clinical improvement without impairment of global ventricular function.

Cardiomyopathy, Hypertrophic↗
PubMed1996

Uptake of iodine-123-alpha-methyl tyrosine by gliomas and non-neoplastic brain lesions.

Using single-photon emission tomography (SPET), the radiopharmaceutical l-3-iodine-123-alpha-methyl tyrosine (IMT) has been applied to the imaging of amino acid transport into brain tumours. It was the aim of this study to investigate whether IMT SPET is capable of differentiating between high-grade gliomas, low-grade gliomas and non-neoplastic brain lesions. To this end, IMT uptake was determined in 53 patients using the triple-headed SPET camera MULTISPECT 3. Twenty-eight of these subjects suffered from high-grade gliomas (WHO grade III or IV), 12 from low-grade gliomas (WHO grade II), and 13 from non-neoplastic brain lesions, including lesions after effective therapy of a glioma (five cases), infarctions (four cases), inflammatory lesions (three cases) and traumatic haematoma (one case). IMT uptake was significantly higher in high-grade gliomas than in low-grade gliomas and non-neoplastic lesions. IMT uptake by low-grade gliomas was not significantly different from that by non-neoplastic lesions. Diagnostic sensitivity and specificity were 71% and 83% for differentiating high-grade from low-grade gliomas, 82% and 100% for distinguishing high-grade gliomas from non-neoplastic lesions, and 50% and 100% for discriminating low-grade gliomas from non-neoplastic lesions. Analogously to positron emission tomography with radioactively labelled amino acids and fluorine-18 deoxyglucose, IMT SPET may aid in differentiating high-grade gliomas from histologically benign brain tumours and non-neoplastic brain lesions; it is of only limited value in differentiating between non-neoplastic lesions and histologically benign brain tumours.

Adult↗
PubMed1996

Reduced GABAA receptor density contralateral to a potentially epileptogenic MRI abnormality in a patient with complex partial seizures.

Imaging cerebral GABAA receptor density (GRD) with single-photon emission tomography (SPET) and iodine-123 iomazenil is highly accurate in lateralizing epileptogenic foci in patients with complex partial seizures of temporal origin. Limited knowledge exists on how iomazenil SPET compares with magnetic resonance imaging (MRI) in this regard. We present a patient with complex partial seizures in whom MRI had identified an arachnoid cyst anterior to the tip of the left temporal lobe. Contralaterally to this structural abnormality, interictal electroencephalography (EEG) performed after sleep deprivation disclosed an intermittent frontotemporal dysrhythmic focus with slow and sharp waves. On iomazenil SPET images GRD was significantly reduced in the right temporal lobe and thus contralaterally to the MRI abnormality, but ipsilaterally to the pathological EEG findings. These data suggest that iomazenil SPET may significantly contribute to the presurgical evaluation of epileptic patients even when MRI identifies potentially epileptogenic structural lesions.

Adult↗
PubMed1996

[Positron emission tomography. Cost-benefit considerations].

To date, positron emission tomography (PET) is the most powerful tool for the non-invasive study of biochemical processes. Besides its usefulness for basic research PET has been proven to be superior to conventional diagnostic methods in several clinical indications. However, the introduction of PET into clinical practice has been hindered considerably by its costs. Several American studies lend support to the hypothesis that PET may be more cost-effective than the conventional diagnostic work-up-at least for some of its clinical indications. In Germany, however, this hypothesis has still not been verified.

Blood Glucose↗
PubMed1996

Neurological impairment and recovery in Wilson's disease: evidence from PET and MRI.

We studied the relationship of regional cerebral glucose consumption (rCMRGlc) and striatal dopamine D2 receptor binding as assessed with positron emission tomography (PET) with the structural abnormalities of the brain in magnetic resonance images (MR), and the degree of neurological impairment in 18 patients with Wilson's disease (WD). The rCMRGlc was determined in the basal ganglia, the thalamus, the cerebral cortex, and the cerebellar hemispheres. The severity of neurological signs, defined by semiquantitative motor impairment scores, correlated highly (r = -0.80) with the reduction of striatal rCMRGlc. Clinical scores, striatal rCMRGlc, and the degree of MRI abnormalities showed no correlation with different indices of dopamine D2 receptor binding. Sequential PET measurements in three patients during treatment with chelating agents revealed a moderate increase of striatal rCMRGlc (in two patients) and a moderate to marked increase of striatal D2 receptor binding (in three patients) in association with clinical improvement. Our data suggest that the rCMRGlc represents a sensitive and objective measure for assessing and monitoring striatal and extrastriatal involvement in WD. The lack of correlation between the dopamine D2 receptor binding and striatal rCMRGlc and structural abnormalities may be explained by the wide spectrum of clinical manifestations and different responses to treatment in WD patients.

Adult↗
PubMed1996

Double-phase Tc-99m MIBI scintigraphy in secondary hyperparathyroidism relapsing after parathyroidectomy and removal of a parathyroid autograft.

A 53-year-old woman with chronic renal failure had secondary hyperparathyroidism relapsing after undergoing a second parathyroidectomy and excision of an autologous parathyroid graft that had been implanted after her first parathyroidectomy. Double-phase scintigraphy with Tc-99m MIBI disclosed pathologic MIBI uptake in the right anterior thorax where the parathyroid transplant had been placed. Histopathologic examination of three nodules excised from this region yielded hyperplastic parathyroid tissue. This case report further illustrates the value of double-phase Tc-99m MIBI scintigraphy in atypical cases of hyperparathyroidism.

Diagnosis, Differential↗
PubMed1996

Influence of size of regions of interest on the measurement of uptake of 123I-alpha-methyl tyrosine by brain tumours.

The aim of this study was to assess the influence of variations in the size of regions of interest (ROIs) on uptake values in brain tumours of L-3-iodine-123-alpha-methyl tyrosine (IMT). In addition, we attempted to establish the influence of size of ROIs on levels of significance assessing differences in mean IMT uptake between high-grade and low-grade tumours. Relative IMT uptake was determined in 19 patients with brain tumours using a MULTISPECT 3 triple-headed camera. Reconstructed image resolution was 14 mm at FWHM. Ten of the subjects suffered from high-grade gliomas (WHO grade III or IV) and nine from benign brain tumours, including eight patients with low-grade gliomas (WHO grade II). ROIs were defined by selecting those pixels within the tumour that exhibited uptake values above predefined threshold values. Using threshold values of 100, 95, 90, 85 and 80% of the mean, transaxial ROI size was approximately 0.1, 2.8, 4.3, 6.2 and 8.8 cm2, respectively. Over this range, mean, IMT uptake values decreased significantly from 2.4 to 1.9. High-grade tumours exhibited significantly higher IMT uptake than low-grade tumours at each of the threshold values. The corresponding levels of significance calculated using the Mann-Whitney U-test were between 0.01 and 0.02. Although IMT uptake values in brain tumours are significantly dependent on ROI size, levels of significance assessing differences in IMT uptake between high-grade and low-grade tumours are relatively insensitive to variations in this parameter.

Adolescent↗
PubMed1996

Secondary parkinsonism due to focal substantia nigra lesions: a PET study with [18F]FDG and [18F]fluorodopa.

We present a 71 year old woman with predominantly right sided parkinsonism of sudden onset, but without tremor. Magnetic resonance imaging (MRI) depicted lesions affecting the substantia nigra (SN) bilaterally, but more pronounced on the left side. There were no other discernible structural lesions. Using positron emission tomography (PET), we investigated regional cerebral metabolic rate of glucose (rCMRG) using the tracer [18F]-fluorodeoxyglucose (FDG), and striatal dopa decarboxylase capacity using the tracer [18F]-L-6-fluorodopa (FDOPA). The degree and pattern of distribution of FDOPA uptake reductions (putamen > caudate nuclei) were similar to those in idiopathic Parkinson's disease (PD). FDG uptake also revealed similar changes (reductions in frontal cortex and cerebellum, but increases in thalamus), except for putamen which showed reduced rCMRG. In conclusion, the absence of tremor at rest accords with experimental SN lesions. The PET findings in this atypical condition are explained in terms of deafferentation of various brain regions involved in motor control. Furthermore, they illustrate the metabolic effects related to acute focal lesions of the SN as opposed to the progressive degeneration in idiopathic PD and may serve to help unravel the complicated pathophysiology underlying these conditions.

Aged↗