Enhancing clinical utility of respiratory-gated PET/CT using patient respiratory trace classification

This work characterizes associations between respiratory trace parameters and improvements in PET image quantification due to gating so as to guide the selection of patients for appropriate motion compensation. Twenty-six lung and liver cancer patients underwent PET/CT exams with recorded abdominal displacement using the Varian RPM system. Static and respiratory-gated [¹⁸F]FDG PET images for each patient were generated from the same list-mode acquisition in 2D or 3D mode on a GE Discovery STE PET/CT scanner, attenuation corrected with helical or phase-averaged cine CT, and reconstructed with OSEM. Patients were grouped by trace type using heuristic classification, by lesion location on diagnostic CT, or by lesion translational freedom on diagnostic CT. FDG PET lesion avidity was quantified with the maximum standardized uptake value (SUV_max). Relative differences (% ASUV_max) between static and gated PET images were calculated across patient groups and compared using an independent 2-sample t-test. No statistically significant differences in % ASUV_max were observed between patients of different trace type (Type 1 vs. 2-3) or lesion translational freedom (detached vs. attached). Lower lung and liver lesions had significantly higher % ASUV_max than upper lung lesions (14% vs. 3%, p <; 0.0001). Linear associations were strongest between % ASUV_max and motion reduction & data fraction (0.42 ± 0.10, r² = 0.59, p <; 0.003) metrics. Patients could be classified according to lesion location between those with significant changes in PET parameters due to respiratory gating and those with negligible changes. Further refinement in patient selection guidelines may enhance respiratory-gated PET/CT utility in therapy target definition and response assessment.