Usefulness of respiratory-gated PET acquisition during delayed ۱۸F-FDG PET/CT scanning for patients with liver metastases

Objective(s): To assess respiratory-gated (RG) positron emission tomography (PET) acquisition for patients with liver metastases during delayed PET/computed tomography (CT) scanning with fluorine-۱۸-fluorodeoxyglucose (۱۸F-FDG).Methods: Nineteen patients with liver metastases who had undergone early whole-body ۱۸F-FDG PET/CT scans without the RG technique and delayed scans with the RG technique were retrospectively selected. The maximum standardized uptake value (SUVmax) of ۴۱ liver lesions and the tumor-to-liver uptake ratios (TLRs) for these same lesions were compared among three data sets: early non-respiratory-gated (early non-RG) images, delayed non-respiratory-gated (delayed non-RG) images, and delayed respiratory-gated (delayed RG) images. In the delayed non-RG and delayed RG images, the improvements in the TLR, relative to the early non-RG images, were assessed according to lesion size.Results: For liver lesions, the SUVmax of early non-RG, delayed non-RG, and delayed RG images were ۶.۵۸±۲.۳۴, ۷.۶۹±۳.۰۸, and ۹.۴۷±۳.۷۳, respectively. There were significant differences among the three images (P<۰.۰۱). The TLR of the delayed RG images was significantly higher than those of the early non-RG and delayed non-RG images (P<۰.۰۱). In the delayed RG images, the difference in the TLR improvement for lesions ≤۱۰ mm in size was ۱۵% higher than that for lesions >۱۰ mm in size; in the delayed non-RG images, the difference in the TLR improvement for the same lesion categories was ۶%.Conclusion: Delayed RG imaging improves the TLR, compared with early non-RG and delayed non-RG imaging, especially for small lesions. RG PET acquisition may be a promising protocol for assessing liver metastases on delayed PET/CT scans.

Keywords:

FDG , Liver Metastases , Respiratory-gated technique , Dual-time-point PET/CT , Tumor-to-liver uptake ratio