Reduced striatal dopamine transmission in REM sleep behavior disorder comorbid with depression.

OBJECTIVE: To investigate dopamine transmission in patients with comorbid REM sleep behavior disorder (RBD) and major depressive disorder (MDD). METHODS: This is a case-control study including 11 medicated patients with comorbid RBD and MDD (mean age 47.5 ± 8.2), 8 medicated patients with MDD only (mean age 47.9 ± 8.4), and 10 healthy participants (mean age 46.5 ± 10.6 years). They underwent clinical assessment, video-polysomnography, olfactory tests, and neuroimaging studies ((18)F-DOPA, (11)C-raclopride, and (18)F-FDG PET neuroimaging). RESULTS: Compared with the 2 control groups, patients with comorbid RBD and MDD had significantly lower (18)F-DOPA uptake at 60 minutes in the putamen and caudate after controlling for age and sex effect (p < 0.05). There were no significant differences for the (11)C-raclopride and (18)F-FDG-PET. The (18)F-DOPA uptake in putamens had significant inverse correlation with severity of RBD symptoms (p < 0.01) and REM-related tonic muscle activity (p < 0.01). The comorbid RBD and MDD group had more impairment in olfactory function. CONCLUSION: Patients with comorbid RBD and MDD had presynaptic dopamine dysfunction and impaired olfactory function. There is a distinct possibility that the development of RBD symptoms among patients with MDD may represent an early phase of α-synucleinopathy neurodegeneration instead of a merely antidepressant-induced condition.

Dual-tracer PET/CT in renal angiomyolipoma and subtypes of renal cell carcinoma.

UNLABELLED: We studied the metabolic characteristics of RCC subtypes and angiomyolipoma with 18F-FDG and 11C-acetate PET/CT. METHODS: Fifty-eight patients with both baseline CT and dual-tracer PET/CT were recruited: 10 angiomyolipoma (16 lesions) and 48 RCC (50 lesions). Each lesion was assessed for SUVmax ratio (lesion-to-normal kidney) on 11C-acetate/18F-FDG PET and attenuation density on CT. Receiver operating characteristic (ROC) curve was analyzed to define the threshold of 11C-acetate SUVmax ratio for differentiating angiomyolipoma from RCC. Thirty-nine RCC patients were selected for 3-year disease-free survival analysis. RESULTS: All angiomyolipoma showed negative 18F-FDG but markedly increased 11C-acetate metabolism, significantly higher than RCC (11C-acetate SUVmax ratio = 4.11 ± 0.53 vs 2.00 ± 0.71; P < 0.05). 11C-acetate SUVmax ratio = 3.71 could differentiate angiomyolipoma including "fat-poor angiomyolipoma" (n = 10) from RCC with sensitivity of 93.8% (15/16) and specificity of 98.0% (49/50). Different RCC subtypes/grades (25 low- and 11 high-grade clear cell [CC], 7 chromophobe, 4 papillary, and 1 collecting duct) were found to have different dual-tracer metabolic pattern (P < 0.05), with overall RCC detection sensitivity of 90% (45/50). All chromophobe RCC were avid only for C-acetate but not 18F-FDG, whereas papillary RCC were primarily the opposite. RCC-CC showed variable dual-tracer uptake: high-grade more avid for F-FDG, low-grade more for 11C-acetate. Four RCC cases negative by dual-tracers were of low-grade RCC-CC. "Primary RCC being 18F-FDG-avid" was the only independent predictor of RCC recurrence in 3 years (P < 0.05), with a median disease-free survival of 22 months. CONCLUSION: 11C-acetate PET/CT helps in differentiating "fat-poor angiomyolipoma" from RCC. Dual-tracer PET/CT has value in diagnosis of RCC subtypes and predicting survival.

[18F]fluoroacetate positron emission tomography for hepatocellular carcinoma and metastases: an alternative tracer for [11C]acetate?

[11C]Acetate (ACT) positron emission tomography/computed tomography (PET/CT) is useful in the detection of hepatocellular carcinoma (HCC). This study aimed to evaluate whether [18F]fluoroacetate (FAC) could be an alternative analogue of [11C]ACT for the diagnosis of HCC. [18F]FAC was synthesized using the precursor t-butyl 2-(methanesulfonyloxy)ethanoate. Five volunteer patients with known HCC were recruited after consent. Whole-body [18F]FAC PET/CT was performed at 20 minutes and 1 hour postinjection and compared to [11C]ACT PET/CT at 20 minutes postinjection to assess biodistribution and tumor uptake characteristics. Qualitative and semiquantitative analyses were performed with statistical correlations on the physiologic organs of accumulation and HCC lesions for both tracers. [18F]FAC was obtained with 99% radiochemical purity, and the reaction yield was 16.0% with 1-hour synthesis time. The biodistribution of [18F]FAC on PET/CT was significantly different from that of [11C]ACT (p < .05) by the lack of preferential uptake in any specific organ, particularly the pancreas, resembling the pattern of blood-pool retention although partly metabolized via the bowel. There was no significant defluorination, and none of the [11C]ACT-avid HCC lesions showed increased [18F]FAC activity. These were different from the results reported on other species. [18F]FAC may not be a potential alternative tracer for [11C]ACT in PET/CT evaluation of HCC in human subjects.

A simple, versatile, low-cost and remotely operated apparatus for [11C]acetate, [11C]choline, [11C]methionine and [11C]PIB synthesis.

A simple, efficient and remotely operated synthesis apparatus for carrying out routine [(11)C]carboxylation, on-column and bubbling [(11)C]methylation was essential for reliable, day-to-day production of [(11)C]-labelled PET radiopharmaceuticals. We developed an in-house apparatus specifically applied to the synthesis of [(11)C]acetate, [(11)C]choline, [(11)C]methionine and 2-(4'-N-[(11)C]methylaminophenyl)-6-hydroxybenzothiazole ([(11)C]PIB), where high radiochemical purity (>or= 97%) and moderate radiochemical yields (18% for [(11)C]PIB, 41-55% for the others) could be achieved. These findings provided evidence that this was a fast, versatile and reliable apparatus suitable for a PET/CT centre with limited financial budget and hot cell space for synthesis of [(11)C]-labelled radiopharmaceuticals.