Dual-phase FDG-PET: delayed acquisition improves hepatic detectability of pathological uptake

The aim of this study was to evaluate whether the acquisition of delayed images could improve the detectability of liver pathological uptakes.

Ninety-five consecutive patients with suspected liver metastases underwent a dual-phase positron emission tomography (PET) scan. All patients underwent a whole-body PET/computed tomography (CT) scan (PET-1) acquired 1 h post [18F]fluorodeoxyglucose (FDG) injection, and a liver PET/CT scan [that is, one or two fields of view (FOV) of the upper abdomen; PET-2] acquired 2 h postinjection. In all cases, image reconstruction was performed as 3D reconstruction algorithm Fourier rebinning (FORE) iterative, FOV 50 cm, image matrix size 128 x 128. Both studies were evaluated qualitatively and semiquantitatively [background standard uptake values (SUV)mean of the liver, lesion SUVmax and SUVmean and ratio SUVmean lesion/background).

Thirty-seven of 95 patients (38.9%) presented liver lesions at both PET-1 and PET-2 exams, whereas there were two (2.2%) only at PET-2. Eighty-one liver lesions were identified at both PET studies, whereas there were nine (11.1%) only at PET-2. Furthermore, at PET-2, we had a statistically significant reduction of SUVmean background values (p < 0.001, Wilcoxon test) and a concomitant increase of SUVmean lesion values (p < 0.001, Wilcoxon test), ratio lesion to background (p < 0.001, Wilcoxon test).

Acquisition of delayed images improved the hepatic detection of pathological FDG uptake.