BackgroundF-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a promising modality for detecting active lesions of cardiac sarcoidosis (CS). However, determining whether 18F-FDG uptake in the myocardium is physiological is challenging due to metabolic shift in myocardial cells. Although methods for inhibiting physiological myocardial 18F-FDG uptake have been proposed, no standard methods exist. This study therefore aimed to compare the effect of an 18-h fast (long fasting (LF)) with heparin loading plus a 12-h fast (HEP) before 18F-FDG PET scan.MethodsWe analyzed the effects of LF and HEP on the inhibition of physiological myocardial 18F-FDG uptake in healthy subjects (18 in HEP and 19 in LF) and in patients with known or suspected CS (96 in HEP and 69 in LF). In CS, the lower uptake of 18F-FDG in the myocardium was evaluated. A visual four-point scale was used to assess myocardial 18F-FDG uptake in comparison with hepatic uptake (1 lower, 2 similar, 3 somewhat higher, 4 noticeably higher).ResultsMyocardial 18F-FDG uptake was 1.68 ± 1.06 in LF and 3.17 ± 1.16 in HEP in healthy subjects (p < 0.0001), whereas it was 1.48 ± 0.99 in LF and 2.48 ± 1.33 in HEP in CS patients (p < 0.0001). Logistic regression and regression trees revealed the LF was the most effective in inhibiting myocardial 18F-FDG uptake. In addition, serum free fatty acid levels on intravenous 18F-FDG injection were a possible biomarker.ConclusionsLF is effective in inhibiting myocardial 18F-FDG uptake, and consequently, it could be useful for evaluating active lesions of CS in 18F-FDG PET images.

FDG-PET/CT is a potentially powerful tool for the early diagnosis of RPC, especially in patients without easily biopsied organ involvement. This modality also facilitates evaluation of disease extent and disease activity during treatment.

The differences in the degree of uptake at each lesion and in uptake patterns at the shoulders and hips are potentially useful for obtaining a definitive diagnosis.

A new tracer, 49-[methyl-11 C]-thiothymidine ( 11 C-4DST), has been developed as an in vivo cell proliferation marker based on the DNA incorporation method. This study evaluated the potential of 11 C-4DST PET/CT for imaging proliferation in nonsmall cell lung cancer (NSCLC), compared with 18 F-FDG PET/ CT. Methods: Eighteen patients with lung lesions were examined by PET/CT using 11 C-4DST and 18 F-FDG. We constructed decay-corrected time-activity curves of 9 major regions as the mean standardized uptake value. We then compared the maximum standardized uptake value (SUVmax) of lung tumors on both 11 C-4DST and 18 F-FDG PET/CT with the Ki-67 index of cellular proliferation and with CD31-positive vessels as a marker of angiogenesis in surgical pathology. Results: NSCLC was pathologically confirmed in 19 lesions of 18 patients. Physiologic accumulation of 11 C-4DST was high in liver, kidney, and bone marrow and low in aorta, brain, lung, and myocardium. Biodistribution of 11 C-4DST was almost stable by 20 min after injection of 11 C-4DST. Mean 11 C-4DST SUVmax for lung cancer was 2.9 6 1.0 (range, 1.5-4.7), significantly different from mean 18 F-FDG SUVmax, which was 6.2 6 4.5 (range, 0.9-17.3; P , 0.001). The correlation coefficient between SUVmax and Ki-67 index was higher with 11 C-4DST (r 5 0.82) than with 18 F-FDG (r 5 0.71). The correlation coefficient between SUVmax and CD31 was low with both 11 C-4DST (r 5 0.21) and 18 F-FDG (r 5 0.21), showing no significant difference between the tracers. Conclusion: A higher correlation with proliferation of lung tumors was seen for 11 C-4DST than for 18 F-FDG. 11 C-4DST PET/CT may allow noninvasive imaging of DNA synthesis in NSCLC.

PurposeThe aims of this study were to evaluate the possibility of using 11C-methionine (11C-MET) and 11C-4′-thiothymidine (11C-4DST) whole-body PET/CT for the imaging of amino acid metabolism and DNA synthesis, respectively, when searching for bone marrow involvement in patients with multiple myeloma (MM) and to compare these findings with those for 18F-FDG PET/CT and aspiration cytology.MethodsA total of 64 patients with MM, solitary plasmacytoma, monoclonal gammopathy of undetermined significance, or an unspecified diagnosis were prospectively enrolled. All the patients underwent three whole-body PET/CT examinations within a period of 1 week. First, the tracer accumulation was visually evaluated as positive, equivocal, or negative for 55 focal lytic lesions visualized using CT in 24 patients. Second, the percentages of marrow plasma cells as calculated using a bone marrow aspiration smear and tracer accumulation were evaluated in the posterior iliac crests of 36 patients.ResultsAmong the 55 lytic lesions, the 11C-MET and 11C-4DST findings tended to reveal more positive findings than the 18F-FDG findings. Based on the standard criteria for the diagnosis of active myeloma using the percentage of marrow plasma cells, significant differences were found between the 18F-FDG and 11C-MET findings and between the 18F-FDG and 11C-4DST findings, but no significant difference was observed between the 11C-MET and 11C-4DST findings.ConclusionThe addition of 11C-MET and 11C-4DST to 18F-FDG when performing PET/CT enabled clearer evaluations of equivocal lesions. Based on cytological diagnostic criteria, 11C-MET and 11C-4DST were more sensitive than 18F-FDG for the detection of active lesions. 11C-MET and 11C-4DST were more useful than 18F-FDG for the detection of active lesions, especially during the early stage of disease.