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.

Cardiac 123I-MIBG uptake in idiopathic ventricular tachycardia and fibrillation.

UNLABELLED: Patients with idiopathic ventricular tachycardia or fibrillation have no additional structural or functional myocardial abnormalities. However, the inducibility of typical tachyarrhythmias by physical or mental stress or by catecholamine infusion suggests the involvement of the adrenergic system in the pathogenesis of these potentially life-threatening diseases. METHODS: 45 patients with idiopathic right ventricular outflow tract tachycardia (RVO-VT), 25 patients with idiopathic left ventricular tachycardia (ILVT), 15 patients with idiopathic ventricular fibrillation (IVF) and 10 age-matched control patients were investigated in this study. Diagnoses were made on the basis of detailed evaluation of the results of two-dimensional echocardiography, left and right ventricular angiography, coronary angiography and endomyocardial biopsy. Local presynaptic norepinephrine re-uptake was assessed using the norepinephrine analog 1231-metaiodobenzylguanidine (MIBG), SPECT and semiquantitative 33-segment bull's-eye analysis. RESULTS: Locally reduced 123I-MIBG uptake was found in 27 of 45 RVO-VT patients (60%), 5 of 15 ILVT patients (33%) and 17 of 25 IVF patients (68%). Unlike ILVT patients, RVO-VT and IVF patients had significantly reduced segmental 123I-MIBG uptake of the posterior wall compared with control patients. CONCLUSION: Patients with idiopathic tachycardia and fibrillation show abnormal 1231-MIBG uptake, which indicates presynaptic sympathetic dysfunction. RVO-VT and IVF patients exhibit significantly reduced 123I-MIBG uptake in the posterior left ventricular wall, whereas ILVT patients do not.

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.

Diagnosis of recurrent glioma with SPECT and iodine-123-alpha-methyl tyrosine.

UNLABELLED: Iodine-123-alpha-methyl tyrosine (IMT) allows the investigation of amino acid transport rate in brain neoplasms. It was the aim of this study to evaluate the potential of IMT-SPECT to diagnose the recurrence of gliomas after primary therapy. METHODS: Using a triple-headed SPECT camera, the cerebral uptake of IMT was determined in 27 patients 22 mo, on average, after surgical removal of a primary brain tumor. Eighteen patients had suffered from high-grade gliomas, and nine had suffered from low-grade tumors. Four patients were examined before and after surgical revision of a presumed tumor recurrence. A total of 31 studies were evaluated. The final diagnosis was based on prospective clinicopathological follow-up. Recurrence was diagnosed in 23 cases, with marked clinical deterioration occurring 3.1 mo, on average, after SPECT, and was confirmed by histopathology in 14 instances. Eight cases were free of recurrence, as evidenced by inconspicuous clinical follow-up, ranging from 6 mo to 17 mo after SPECT in seven cases, and by clinical course and histopathology in the remaining subject. RESULTS: Patients with recurrence had significantly higher ratios of IMT uptake in the tumor area to that in a background region than did patients without recurrence (2.27 +/- 0.59 compared to 1.47 +/- 0.29; p < 0.002). The best cutoff level of the IMT uptake ratio in the differentiation between recurrence and benign posttherapeutic lesion was 1.8. Using this study-specific discrimination threshold, the sensitivity and specificity of IMT-SPECT for detecting glioma recurrence were 18 of 23 (78%) and 8 of 8 (100%), respectively. The area under the binormal receiver operating characteristic curve, fitted to the data, was 0.90 +/- 0.06. CONCLUSION: Iodine-123-alpha-methyl tyrosine-SPECT is a promising new tool in the follow-up of patients with gliomas after primary therapy.

Disturbed benzodiazepine receptor function at the onset of temporal lobe epilepsy--lomanzenil-binding in de-novo TLE.

PURPOSE: Epileptogenic foci exhibit disturbed function at the level of the benzodiazepine receptor. The aim of our study was to investigate the incidence of focal reductions of temporal benzodiazepine receptor binding (BRB) as assessed by scintigraphy with 123I-iomazenil in patients with denovo temporal lobe epilepsy (TLE). METHODS: Forty adult patients (age: 34+/-12 years) with cryptogenic denovo TLE underwent scintigraphy with 123I-iomazenil. In all patients, symptomatic epilepsy was excluded by clinical investigation and MRI. The median duration of TLE was seven months, and the patients had a median of three documented seizures in their history of disease. BRB was quantified in four temporal regions covering the whole temporal lobe. Temporal asymmetry values (ASY) were compared with data determined in 13 age-matched controls yielding Z-scores for global and regional temporal BRB. RESULTS: A significant reduction of temporal BRB was found in 19 of the 40 patients (48 %), mainly in mesial temporal regions; temporal BRB asymmetries were also found in patients with a short history of seizures and low seizure frequency (< or = 1 year; n = 32, 13/32 (41 %)). Only in the entire cohort did the magnitude of temporal reduction of BRB correlate with the duration of TLE as well as with the number of previous partial seizures (r = 0.40 and r = 0.36; p < 0.03, respectively). CONCLUSIONS: Foci of decreased BRB can already be detected at the onset of TLE; their magnitude is related to ongoing epileptic activity.

I-123-lodo-alpha-methyl tyrosine SPECT in non-parenchymal brain tumours.

PURPOSE: Scintigraphy using I-123-iodo-alpha-methyl tyrosine (IMT) is useful in the preoperative characterization of gliomas, in detecting recurrent glioma and in the biological re-evaluation of residual or recurrent tumours. A systematic evaluation of non-parenchymal brain tumours has not yet been performed. The aim of the present study was to evaluate IMT SPECT in the management of intracerebral metastases and lymphomas. PATIENTS AND METHODS: IMT uptake was analyzed in 31 patients with 28 metastases of extracerebral solid tumours and 7 cerebral lymphomas. Histology revealed high grade lymphomas, melanomas, and carcinomas of the following origin: lung, unknown primary, breast, colon, renal cell, ovary, vagina, frontal sinus. IMT uptake was quantified as ratio between maximal tumour accumulation and average uptake in the contralateral hemisphere. RESULTS: All tumours except two renal cell and one small cell lung carcinoma metastases accumulated IMT (91%). The highest IMT uptake was found in a metastasis of lung carcinoma. IMT uptake was highly variable and was similar in primary and in recurrent tumours. CONCLUSION: Significant accumulation of IMT is seen in the majority of tumours, so that this technique might be helpful for the management of cerebral metastases and lymphomas.

[The role of L-3-I-123-iodine-alpha-methyltyrosine SPECT in cerebral gliomas]. / Die Bedeutung der L-3-I-123-Iod-alpha-Methyl-Tyrosin-SPECT bei zerebralen Gliomen.

L-3-I-123-iodine-alpha-methyltyrosine (IMT) is a I-123-labelled amino acid which has been used for single photon emission computed tomography (SPECT) of cerebral gliomas for more than a decade. IMT-SPECT is able to detect tumor infiltration independent of disruptions of the blood-brain barrier which is often difficult with computed tomography or magnetic resonance tomography. The method is useful to detect tumor recurrences and helps to distinguish gliomas from non-neoplastic brain masses. IMT-SPECT is thus a valuable tool in the diagnostic evaluation and in therapy planning of patients with cerebral gliomas.

Moyamoya syndrome: impaired hemodynamics on ECD SPECT after EEG controlled hyperventilation.

BACKGROUND AND PURPOSE: Ischemic symptoms in children with Moyamoya syndrome are typically provoked by hyperventilation (HV) and are accompanied by the "re-build-up" phenomenon in EEG. The value of scintigraphic detection of HV-provoked perfusion deficits remains to be elucidated. PATIENTS AND METHODS: In seven children with Moyamoya syndrome regional cerebral blood flow was assessed by 99mTc-ethyl-cysteine-dimer (ECD) single photon emission computed tomography (SPECT) after HV and under baseline conditions to identify ischemia prone regions. RESULTS: Regional marked hypoperfusion after HV was found in all patients. Predominant perfusion deficits were detected in the frontal lobes. CONCLUSION: ECD SPECT is a potential tool for the preoperative evaluation of cerebral hemodynamics and for monitoring angiosurgical therapies in Moyamoya disease.

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.

201Tl reinjection predicts improvement of left ventricular function following revascularization.

The aim of this study was to evaluate the correlation between improved Tl uptake in reinjection imaging with improvements in regional wall motion and global ejection fraction following PTCA or aorto-coronary bypass surgery. 19 patients with CHD were investigated and divided into two groups according to their thallium uptake in the reinjection studies. Group I showed additional uptake on reinjection imaging compared to the redistribution image, whereas group II showed no additional uptake. Both groups had a similar number and distribution of affected vessels and location of the leading stenosis. Stress, redistribution and reinjection images were obtained prior to revascularization and evaluated semiquantitatively from a bulls eye scheme. There was a postoperative increase in regional wall motion in group 1 from 5.3 to 8.8% whereas group II did not show a relevant change (6.3 vs 6.0%). The ejection fraction increased II from 55.0 to 66.7% in group I and dit not increase in group II (59.8 vs 58.7%). The overall predictive value of the reinjection image for improvement in wall motion (> 10%) was 91% and for the redistribution image 58%. Increased uptake in reinjection imaging predicts improved ventricular function following revascularization and indeed indicates viable myocardium with reversible functional impairment.

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.

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.

Drug-induced changes in cerebral glucose consumption in bifrontal epilepsy.

PURPOSE: Positron emission tomography (PET) using 18F-radiolabeled deoxyglucose (18F-FDG) is a sensitive procedure for detection of epileptogenic foci. Although alterations in glucose consumption are not restricted to the area of seizure generation itself, the magnitude and extent of cerebral metabolic disturbances induced by epileptic discharges can be detected. Despite two decades of epilepsy research using 18F-FDG-PET, little is known about the metabolic changes during therapy of focal epilepsy. We report on a child with frontal epilepsy with severe glucose hypometabolism that was nearly completely normalized during drug therapy. METHODS: Interictal 18F-FDG-PET was performed at the onset of epilepsy and after optimized drug therapy in a 5-year-old boy with behavioral abnormalities and repetitive seizures of frontal origin with bifrontal interictal EEG slowing for 8 weeks. Both scans were anatomically matched; initial and intratherapeutic glucose metabolism were compared. RESULTS: In accordance with the epileptogenic focus as identified by EEG and ictal/interictal perfusion single-photon emission tomography (SPECT), bifrontal hypometabolism was depicted by 18F-FDG-PET. Magnetic resonance imaging (MRI) was unremarkable. After dual-drug therapy (valproate, carbamazepine), the boy became seizure free, and his initial behavioral deficits disappeared. A control PET study after 3 months of therapy showed restored glucose consumption; the frontal EEG slowing was normalized. CONCLUSIONS: This case demonstrates that reduction of glucose metabolism in epileptogenic foci may be a result of reversible neuronal dysfunction that correlates with the electroclinical follow-up.

Positron emission tomography with F-18-deoxyglucose in patients with differentiated thyroid carcinoma, elevated thyroglobulin levels, and negative iodine scans.

INTRODUCTION: In patients with differentiated thyroid carcinoma, elevated serum levels of thyroglobulin (hTg) may occur in spite of otherwise negative diagnostic procedures and in particular in spite of a negative iodine-131 scan. Positron emission tomography with F-18-deoxyglucose (FDG-PET) is a potentially useful method for the detection of metastatic lesions or the recurrence of thyroid cancer. We aimed to investigate whether FDG-PET is capable of detecting metastatic lesions or recurrence in patients with differentiated thyroid carcinoma, elevated serum levels of thyroglobulin, and otherwise negative diagnostic procedures, including the iodine-131 scan. METHODS: From a group of 500 patients with differentiated thyroid carcinoma, a subgroup of 32 patients had elevated serum hTg-levels, negative iodine- 131 scans, negative cervical and abdominal ultrasound, and negative X-ray of the chest. In 12 of these patients (hTg 77.8+/-94.3 ng/ml, range 1.5-277 ng/ml, median 20 ng/ml), FDG-PET was performed. All but one FDG-PET study was performed in a state of hypothyroidism (TSH 75.8+/-32.2 microIU/ml, range 31-116 microIU/ml, median 74.6 microIU/ml). RESULTS: In 6 of the 12 patients investigated, the FDG-PET was positive. In three of the patients, the diagnosis was confirmed by computed tomography or magnetic resonance imaging. In patients with a positive FDG-PET finding, the hTg level was 146.7+/-90.1 ng/ml (23-277 ng/ml, median 144.5 ng/ml). In contrast, in patients with a negative finding the hTg level was only 9.0+/-7.6 ng/ml (range 1.5-17 ng/ml, median 8.1 ng/ml), P=0.01. CONCLUSION: These preliminary results show that in patients with differentiated thyroid carcinoma, elevated hTg levels, and otherwise negative "conventional" diagnostic procedures, FDG-PET is helpful in detecting metastatic lesions.

[Positron emission tomography. Cost-benefit considerations]. / Positronenemissionstomographie. Kosten-Nutzen-Gesichtspunkte.

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.

Imaging sympathetic innervation.

The autonomic innervation of the heart modifies most cardiac functions. Especially the heart rate and the force of contraction of myocytes are modulated by the autonomic nervous system. A number of specific neurotransmitters interact with receptors on post- and presynaptic binding sites regulating the complex electromechanical system of the heart. Disturbances at this interaction result in a variety of cardioneuropathies. The clinical manifestations can be mild and may only consist of sporadic arrhythmias without hemodynamic effects. In some cases however the autonomic dysfunction may be severe, e.g. in the acute phase of the Guillain-Barré syndrome and in advanced diabetic neuropathy. At present, the only available techniques to visualise and quantitate disbalanced innervation of the myocardium are scintigraphic modalities as single photon emission tomography (SPECT) and positron emission tomography (PET) with appropriate radiopharmaceuticals. These methods are reviewed with respect to their possible clinical application and to future developments.

Thallium-201 single photon emission tomography of myocardium: additional information in reinjection studies is dependent on collateral circulation.

A second thallium-201 injection under resting conditions is able to improve the differentiation between myocardial scar and ischaemia when compared with simple redistribution imaging. The aim of this study was to evaluate the dependence of this improvement on the degree of stenosis and the presence of collaterals. Single photon emission tomography (SPET) studies under exercise, redistribution and reinjection conditions were performed on 84 patients with 181 stenotic vessels (70 left anterior descending, 47 left circumflex, 64 right coronary artery) and compared with angiography. An improvement of the 201Tl uptake in the reinjection image was observed in 53% of the myocardial areas served by a coronary artery with a stenosis of over 90%. This is compared with 13% of the areas served by a vessel with a stenosis between 50% and 90%. 90% of the collateralized areas showed a fill-in effect, but only 7 of the 118 without angiographically visible collateralization (6%). The dependence of the fill-in effect, collateralization and stenosis was highly significant (chi 2 test, p less than 0.0001). In our patient group, there was much greater benefit from the reinjection study in vessels with a greater than 90% narrowing. The fill-in effect was closely correlated to the presence of collaterals. In these cases, the fill-in may be an indication for hibernating myocardium.