Increasing Uptake Time in FDG-PET: Standardized Uptake Values in Normal Tissues at 1 versus 3 h

Abstract

On FDG imaging at 3 h compared to 1 h, significant changes were apparent, but the magnitude of changes was modest overall. Three-hour delayed imaging demonstrated significantly lower aortic blood pool and adipose tissue activity and significantly higher cerebellum, muscle, spleen, and bone marrow activity. Hepatic and lung activities were not significantly different. These results suggest that previously reported improvements in tumor image contrast with delayed imaging may be primarily due to cumulative FDG uptake within the tumor rather than reduction in normal background activity.

The Role of Delayed 18F-FDG PET Imaging in the Follow-up of Patients with Alveolar Echinococcosis

“…In this way, delayed acquisition increased the number of results that were doubly true-positive and for which treatment interruption was thus contraindicated. Also the number of doubly true-negative results was improved by delayed 18 F-FDG PET because we observed 12 patients with negative serology after standard PET (Fig. 2) versus 7 patients after delayed acquisition, thus further reducing the number of patients who could be subjected to treatment interruption.…”

“…Follow-up Therapeutic efficiency was evaluated by clinical and ultrasound examinations, liver tests, blood counts, and serology every 6 mo. 18 F-FDG PET was performed every 6-12 mo, depending on the severity of the disease.…”

“…In 2 patients, the serology was borderlinepositive, but since it had remained stable for 26 and 11 mo in the absence of perilesional 18 F-FDG uptake on delayed 18 F-FDG PET, benzimidazole was stopped nevertheless and the patients were followed up more closely; one of these patients wanted to become pregnant, in which case benzimidazole drugs need to be discontinued as they are teratogenic (5). All 7 patients, including the patients with borderline serology, had an uneventful favorable outcome after treatment interruption (mean duration of follow-up, 23 mo; range, 8-37 mo); there was no evidence of disease recurrence, and no positive 18 F-FDG PET findings (either at the standard or the delayed acquisition) were observed during the follow-up.…”

“…A negative specific serology in patients who had a positive serology before treatment initiation is statistically associated with clinical improvement and relative stability of the lesions but, on an individual basis, cannot assess absence of E. multilocularis viability (9). 18 F-FDG PET with wholebody acquisition 1 h after radiopharmaceutical intravenous injection has been proposed as a functional surrogate marker (7,8,10,11); however, attempts at treatment interruption according to complete loss of perilesional 18 F-FDG uptake have often been followed by reevolution of the lesions (12). This pattern strongly suggests that the parasite was still viable and that 18 F-FDG uptake might have been underestimated and misinterpreted.…”

“…Koyama et al showed that delayed 18 F-FDG PET image acquisition (2 h after 18 F-FDG injection), also called dual-time-point imaging, improved detection of malignant hepatic lesions (13). Lin et al demonstrated that tumor-to-background ratio in the liver was even higher at a 3-h acquisition than at a 2-h acquisition (14), and further studies confirmed that an improvement of tumor-to-background ratio with better visualization of liver tumors could be obtained by delayed 18 F-FDG PET (15)(16)(17)(18).…”