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.

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.

Fluorine-18 fluorodeoxyglucose positron emission tomography in medullary thyroid cancer: results of a multicentre study.

The aim of this study was to evaluate the clinical use of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) in medullary thyroid cancer (MTC) on the basis of comparison with findings obtained using indium-111 pentetreotide (SMS), pentavalent technetium-99m dimercaptosuccinic acid (DMSA), technetium-99m sestamibi (MIBI), computed tomography (CT) and magnetic resonance imaging (MRI). One hundred FDG-PET examinations in 85 patients (40 males, 45 females) with elevated tumour marker levels and/or pathological findings on other imaging methods were evaluated retrospectively. Eighty-two patients were examined after total thyroidectomy, and the remaining three patients prior to surgery. Overall, 181 lesions could be identified with at least one of the imaging techniques. Fifty-five lesions were confirmed histologically. FDG-PET detected 123 of 181 sites, which is a lesion detection probability of 68%. In the 55 cases with histological confirmation, we found 32 true positive, 3 false positive, 11 true negative and 9 false negative lesions using FDG-PET, resulting in a sensitivity of 78% and a specificity of 79%. Sensitivity and specificity were, respectively, 25% and 92% for SMS, 33% and 78% for DMSA, 25% and 100% for MIBI, 50% and 20% for CT and 82% and 67% for MRI. Compared with morphological techniques and functional imaging methods with single-photon emitters, FDG-PET showed the highest lesion detection probability for MTC tissue, with a high sensitivity and specificity. It is concluded that FDG-PET is a useful method in the staging and follow-up of MTC.

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.

Temporal hypometabolism at the onset of cryptogenic temporal lobe epilepsy.

Most patients with intractable temporal lobe epilepsy (TLE) exhibit temporal glucose hypometabolism. The reasons for the development of this abnormality are as yet unclear. The current notion is that an initial injury causes seizures, which in turn give rise to hypometabolism. The aim of this study was to assess whether temporal reductions in glucose metabolism in non-lesional TLE are the result of repeated seizures or whether hypometabolism represents an initial disturbance at the onset of disease. Glucose consumption was assessed with fluorine-18 fluorodeoxyglucose positron emission tomography (18F-FDG PET) in 62 patients with cryptogenic non-refractory TLE in different stages of disease. Twelve subjects without neurological illness served as controls. Patients with onset of epilepsy at least 3 years prior to the PET scan were defined as having chronic TLE. Using this criterion, the whole patient cohort included 27 patients with de novo TLE and 35 patients with chronic TLE. The groups were matched for age and sex. The appearance of high-resolution magnetic resonance images of the brain was unremarkable in all patients. In the total cohort, number, duration and frequency of seizures had a significant relation to the magnitude of hypometabolism. Temporal hypometabolism was exhibited by 26 of the 62 patients (42%), including 8 out of 27 (30%) with newly diagnosed TLE and 18 out of 35 (51%) with chronic TLE. The disturbances were more extensive and more severe in patients with chronic TLE. It is concluded that temporal hypometabolism may already be present at the onset of TLE, but is less frequent and less severe in newly diagnosed than in chronic TLE. The metabolic disturbance correlates with the number of seizures. These findings suggest that an initial dysfunction is present in a considerable number of patients and that hypometabolism is worsened by continuing epileptic activity.

High uptake of L-3-[123I]iodo-alpha-methyl tyrosine in pilocytic astrocytomas.

Despite a favourable prognosis, pilocytic astrocytomas may exhibit signs of malignancy on various neuroimaging modalities. This retrospective analysis was conducted to determine whether scintigraphic features of malignancy are also found on single-photon emission tomography (SPET) using L-3-[123I]iodo-alpha-methyl tyrosine (IMT) as a tracer. Twenty patients with pilocytic astrocytomas were retrospectively selected from a large series of patients referred for the evaluation of primary or recurrent brain tumours. IMT SPET was performed in 16 patients, positron emission tomography (PET) using 2-[18F]fluoro-2-deoxy-D-glucose (FDG) was available in 10 of the patients and SPET using technetium-99m tetrofosmin or thallium-201 had been performed in 11. Image analysis was performed using standard protocols to determine how many patients exceeded the respective thresholds of malignancy. Features of malignancy were found in 7/16 IMT SPET studies, in 7/10 FDG PET studies and in 7/11 of the residual SPET investigations. A significant correlation of tumour size and IMT uptake in primary pilocytic astrocytomas indicated partial volume effects to partly account for the differential uptake behaviour (n = 10, r = 0.87, P < 0.05). Differences in IMT uptake in primaries (1.7 +/- 0.6, n = 10) and in recurrent tumours (2.3 +/- 0.7, n = 6) did not attain statistical significance. IMT SPET results indicative of malignancy are regularly found in pilocytic astrocytomas, despite their good prognosis. No uptake may be detected in largely cystic or in small tumours.

Sequential scintigraphic strategy for the differentiation of brain tumours.

Both thallium-201 and iodine-123 alpha-methyltyrosine (123I-IMT) have been shown to be useful in the diagnostic evaluation of brain tumours. The aim of this study was to investigate the respective contributions of 201Tl and 123I-IMT single-photon emission tomography (SPET) in the non-invasive evaluation of intracerebral tumours. We analysed 65 patients with the following brain tumours: 8 non-neoplastic lesions, 4 meningiomas, 12 low-grade gliomas, 28 high-grade gliomas, 11 metastases and 2 high-grade lymphomas. 201Tl SPET and 123I-IMT SPET were performed [start of 201Tl SPET: 15 min p.i. (early) and 180 min p.i. (delayed); start of 123I-IMT SPET: 15 min p.i.]. The intensity of uptake was quantified as the ratio between tracer accumulation in the tumour and in the contralateral hemisphere. None of the non-neoplastic lesions or low-grade gliomas expressed marked 201Tl uptake. All malignant tumours except one small metastasis and all meningiomas except one small, cystic and degenerated lesion showed significant 201Tl accumulation [Tl(15')>2.0]; 123I-IMT uptake was either absent or intermediate in non-malignant lesions except in two low-grade gliomas; the highest levels were observed in high-grade gliomas followed by metastases and lymphomas (mean IMT: 2.7 vs. 2.1 vs. 1.8), with metastases showing a high variability in 123I-IMT uptake (range: 0.8-3.6). Using 201Tl to distinguish non-neoplastic lesions from malignant tumours and meningiomas, 63 of 65 patients were characterised correctly. In the latter group, high-grade gliomas were correctly identified in 27 of 28 cases by their amino acid uptake. It is concluded that the combination of 201Tl and 123I-IMT surpasses the accuracy of each single test in the differentiation of space-occupying lesions of the brain. Based on these preliminary results, a sequential strategy is proposed involving an initial 201Tl SPET study and an additional 123I-IMT SPET study in the event of positive 201Tl uptake.

Evaluation of the extension of cerebral gliomas by scintigraphy.

BACKGROUND: Single photon emission computed tomography (SPECT) with 201Tl and 123I-alpha-methyl tyrosine (123I-IMT) are routine methods for the evaluation of brain tumors. 123I-IMT transport across the blood brain barrier is mediated by an amino acid carrier, 201Tl accumulation is analogous to cerebral potassium uptake. PATIENTS AND METHODS: To determine the differences in glioma extension as shown by the 2 methods, 17 patients with malignant gliomas were included in this comparative imaging study: astrocytoma III: n = 6, ependymoma III: n = 1, oligodendroglioma III: n = 1, glioblastoma IV: n = 9. The tomographic image sets were matched anatomically and the slices showing maximal tumor extension were identified in both image sets respectively. Tumor spread was compared visually and the tumor extension was quantified. RESULTS: In gliomas WHO III tumor extension was delineated significantly larger by 123I-IMT-SPECT than by 201Tl-SPECT (mean +/- SD: 816 +/- 281 pixels vs 600 +/- 220 pixels, n = 8, p < 0.05). The size of glioblastomas was shown in a comparable manner by the 2 methods (977 +/- 571 vs 1.051 +/- 588, n = 9, ns, p = 0.57), but there were considerable regional differences between the area of 201Tl uptake and amino acid retention. In the whole group a weak but significant negative correlation between intensity of 201Tl uptake on the one hand and a ratio of the area as depicted by 123I-IMT vs area as depicted by 201Tl on the other hand, was found (n = 17, r = 0.49, p < 0.05). Thus the differences in the delineation of areas became smaller with increasing 201Tl uptake. CONCLUSIONS: These preliminary data indicate that the extension of gliomas is depicted differently by the 2 methods. 123I-IMT-SPECT shows a larger tumor extension especially in gliomas WHO III. Since 201Tl uptake has previously been shown to correlate with disruption of the blood brain barrier, 123I-IMT-SPECT may delineate tumor parts without endothelial leakage. This additional information may be helpful in planning surgical or radiation therapy. The advantages of 123I-IMT in this respect decrease with increasing 201Tl uptake and with increasing malignancy.

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.

Clinical evaluation of no-carrier-added meta-[123I]iodobenzylguanidine for myocardial scintigraphy.

In clinical and research studies, images obtained using carrier-added meta-[123I]iodobenzylguanidine (c.a. [123I]MIBG) have shown quite variable quality, with varying levels of uptake in lung, liver and mediastinum; this is a significant problem for quantification of the myocardial uptake by means of region ratios. First experimental and preliminary human data in respect of no-carrier-added (n.c.a.) [123I]MIBG are indicative of improved imaging quality. The aim of the present study was to evaluate the clinical value of myocardial scintigraphy with n.c.a. [123I]MIBG in patients with tachyarrhythmias. The study population comprised 24 patients with tachyarrhythmogenic diseases routinely studied by cardiac single-photon emission tomography (SPET) with [123I]MIBG. Twelve of the 24 patients were studied with c.a. [123I]MIBG (seven females and five males; mean age 42+/-13 years, range 20-60 years), whereas the other 12 were studied with n.c.a. [123I]MIBG (ten females, two males; mean age 41+/-11 years, range 18-60 years, P=NS). For quantification of the specific uptake in the different organs, count ratios were calculated on SPET images acquired 4 h p.i. Visual analysis of all [123I]MIBG scans showed improved image quality (improved contrast between heart and neighbouring organs) in n.c.a. studies as compared with c.a. studies. A significantly higher heart/left atrial blood ratio was found in the n.c.a. studies as compared with the c.a. studies (10.3+/-3.2 vs 5.3+/-1.3, P=0.0003); furthermore, significantly higher heart/lung and heart/liver ratios (2.5+/-0.6 vs 1.5+/-0.3, P=0.0002, and 0.8+/-0.2 vs 0.6+/-0.1, P=0.0006, respectively) were obtained in the c.a. studies, whereas lung/left atrial blood and liver/left atrial blood ratios showed no significant differences (4.2+/-1.3 vs 3.6+/-1.1, P=0.39, and 13.7+/-5.2 vs 9.6+/-2.2, P=0.21, respectively). In conclusion, the use of n.c.a. [123I]MIBG yields a significantly higher myocardial uptake associated with improvement in contrast between the heart and neighbouring organs and is therefore superior to the commercially available c.a. [123I]MIBG for use in clinical and research studies of the myocardial presynaptic sympathetic nervous system. Furthermore, our data indicate that for quantification the use of a left atrial blood reference region of interest, which is only available on SPET studies, is to be recommended.

[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.

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.

[Cidofovir (vistide) in therapy of progressive multifocal leukoencephalopathy in AIDS. Review of the literature and report of 2 cases]. / Cidofovir (Vistide) in der Therapie der Progressiven Multifokalen Leukoenzephalopathie (PML) bei AIDS. Literaturübersicht und Beschreibung zweier Fälle.

The progressive multifocal leukoencephalopathy (PML), a complication of the acquired immunodeficiency syndrome (AIDS) in 4%-5% of all cases, is an encephalitis caused by the JC papovavirus. The prognosis is very poor with a mean survival time after diagnosis of 3 to 6 months. No effective therapy is known to date. Therapeutic trials in small groups of patients with alpha-interferon, didanosine, and arabinoside were of minor success. A controlled study with cytarabine did not show any efficacy. Single case reports on a therapy with cidofovir (Vistide), an approved nucleotide-analogone in the therapy of cytomegalovirus-retinitis in AIDS-patients without renal dysfunction, showed positive results. We describe 2 more cases of a therapy of cidofovir in AIDS-associated PML. Out of 22 cases described in the literature, including these 2 cases, with a therapy of cidofovir in AIDS-associated PML, 16 patients improved under therapy, 2 remained stable, and only 4 patients still worsened fulminantly. These results indicate an additive antiviral effect of cidofovir against JC-virus. This may be used in the therapy of PML in AIDS-patients because no alternative antiviral therapy of PML is available at present. The efficacy of cidofovir for the therapy of PML is suggested by case reports. The exact mechanisms leading to an improvement under a therapy with cidofovir in the 16 cases described so far should be evaluated in a randomised, controlled study with an adequate size of cohorts.

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.

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.

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.