Henk Stevens

OBJECTIVE: The authors examine the functional anatomy of serotonergic and dopaminergic systems in obsessive-compulsive disorder in psychotropic-naive patients without comorbidity. METHOD: [(123)I]beta-CIT binding patterns for dopamine and serotonin transporters in the brain were measured in 15 psychotropic-naive adult outpatients with OCD (no comorbidity) and in 15 pairwise-matched healthy subjects. Volumes of interest were constructed on magnetic resonance imaging scans and coregistered with single photon emission computed tomography scans. Binding ratios were compared, and possible correlations between binding patterns and obsessive-compulsive symptoms were assessed. RESULTS: There were significant differences between patients and healthy subjects in the [(123)I]beta-CIT binding pattern for dopamine transporter in the left caudate and left putamen. Patients had higher binding ratios than healthy subjects. No differences were found in the less specific [(123)I]beta-CIT binding pattern for serotonin transporters in the selected volumes of interest. Hemispheric within-group comparisons revealed no asymmetry effects. CONCLUSIONS: The results of our study provide direct evidence for an involvement of the dopaminergic system in the pathophysiology of OCD.

UNLABELLED: There is circumstantial evidence for the involvement of serotonergic and dopaminergic systems in the pathophysiology of social anxiety disorder. In the present study, using SPECT imaging we examined the (123)I-beta-(4-iodophenyl)-tropane binding potential for the serotonin and dopamine transporters in patients with a generalized social anxiety disorder and in age- and sex-matched healthy controls. METHODS: Twelve psychotropic medication-naïve patients with social anxiety disorder, generalized type (5 women and 7 men) and 12 sex- and age-matched healthy controls were studied. Volumes of interest were constructed on MRI-coregistered SPECT scans. Binding ratios were compared using the Mann-Whitney U test. Possible correlations between binding patterns and symptomatology were assessed using the Spearman rank correlation coefficient. RESULTS: Significantly higher binding potentials were found for the serotonin in the left and right thalamus of patients. Patients had also a significantly higher binding potential for the dopamine transporter in the striatum. CONCLUSION: The present study provided direct evidence for abnormalities in both the dopaminergic and the serotonergic systems in patients with generalized social anxiety disorder.

Recently introduced PET systems using silicon photomultipliers with digital readout (dPET) have an improved timing and spatial resolution, aiming at a better image quality than conventional PET (cPET) systems. We prospectively evaluated the performance of a dPET system in patients with cancer, as compared with high-resolution (HR) cPET imaging. <b>Methods:</b> After a single ¹⁸F-FDG injection, 66 patients underwent dPET and cPET imaging in randomized order. We used HR reconstructions (2 × 2 × 2 mm voxels) for both scanners and determined SUV_max, SUV_mean, lesion-to-background ratio (LBR), metabolic tumor volume (MTV), and lesion diameter in up to 5 ¹⁸F-FDG–positive lesions per patient. Furthermore, we counted the number of visible and measurable lesions on each PET scan. Two nuclear medicine specialists determined, in a masked manner, the TNM score from both image sets in 30 patients referred for initial staging. For all 66 patients, these specialists separately evaluated image quality (4-point scale) and determined the scan preference. <b>Results:</b> We included 238 lesions that were visible and measurable on both PET scans. For 27 patients, we found 37 additional lesions on dPET (41%) that were unmeasurable (<i>n</i> = 14) or invisible (<i>n</i> = 23) on cPET. Mean (±SD) SUV_mean, SUV_max, LBR, and MTV on cPET were 5.2 ± 3.9, 6.9 ± 5.6, 5.0 ± 3.6, and 2,991 ± 13,251 mm³, respectively. On dPET, SUV_mean, SUV_max, and LBR increased by 24%, 23%, and 27%, respectively (<i>P</i> &lt; 0.001) whereas MTV decreased by 13% (<i>P</i> &lt; 0.001), compared with cPET. Visual analysis showed TNM upstaging with dPET in 13% of the patients (4/30). dPET images also had higher scores for quality (<i>P</i> = 0.003) and were visually preferred in most cases (65%). <b>Conclusion:</b> dPET improved the detection of small lesions, upstaged the disease, and produced images that were visually preferred to those from HR cPET. More studies are necessary to confirm the superior diagnostic performance of dPET. <b>Keywords:</b> digital PET; conventional PET; FDG PET; lesion detection; cancer imaging

The aim of this study was to determine whether it is possible to differentiate between recurrent disease and post-treatment necrosis in patients treated for a primary brain tumour. This prospective study was designed to compare the sensitivity and specificity of 201Tl single photon emission tomography (SPET) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) using a dual-headed coincidence camera. Sixteen patients suspected of having recurrent brain tumour (10 men, 6 women) (mean age 39.5 years, range 21-57 years) were studied. 201Tl SPET and 18F-FDG PET studies were performed on the same day. An increase in activity was considered indicative of tumour recurrence. The images were also quantified using a thallium index and an FDG index. The 18F-FDG PET images were also assessed visually using a 5-point scale. The diagnosis of tumour recurrence was based on clinical course and/or follow-up computed tomography or magnetic resonance imaging. The sensitivity of 201Tl SPET and 18F-FDG PET was 92% (11/12) and 62% (7/12) respectively. One patient initially assessed as having necrosis showed a recurrence 9 months after both studies. McNemar's analysis of these results showed a statistically significant difference (P = 0.023) in the ability of the two methods to separate with accuracy tumour from radiation necrosis. No correlation was found between the thallium index and the FDG index (r = 0.36). We conclude that 201Tl SPET is a sensitive modality for the detection of brain tumour recurrence. 18F-FDG imaging using a dual-headed coincidence camera gave significantly poorer results compared to 201Tl SPET. Our results do not justify continuation of this prospective comparative study.