Usefulness of respiratory-gated PET acquisition during delayed 18F-FDG PET/CT scanning for patients with liver metastases

Document Type : Technical note


1 Division of Positron Emission Tomography, Institute of Advanced Clinical Medicine, Kindai University Hospital, Osaka, Japan

2 Department of Radiology, Kindai University Faculty of Medicine, Osaka, Japan


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-18-fluorodeoxyglucose (18F-FDG).
Methods: Nineteen patients with liver metastases who had undergone early whole-body 18F-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 41 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 6.58±2.34, 7.69±3.08, and 9.47±3.73, respectively. There were significant differences among the three images (P<0.01). The TLR of the delayed RG images was significantly higher than those of the early non-RG and delayed non-RG images (P<0.01). In the delayed RG images, the difference in the TLR improvement for lesions ≤10 mm in size was 15% higher than that for lesions >10 mm in size; in the delayed non-RG images, the difference in the TLR improvement for the same lesion categories was 6%.
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.


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