Respiratory motion correction in F-18-FDG PET/CT impacts lymph node assessment in lung cancer patients

Abstract

BackgroundsElastic motion correction in PET has been shown to increase image quality and quantitative measurements of PET datasets affected by respiratory motion. However, little is known on the impact of respiratory motion correction on clinical image evaluation in oncologic PET. This study evaluated the impact of motion correction on expert readers’ lymph node assessment of lung cancer patients.MethodsForty-three patients undergoing F-18-FDG PET/CT for the staging of suspected lung cancer were included. Three different PET reconstructions were investigated: non-motion-corrected (“static”), belt gating-based motion-corrected (“BG-MC”) and data-driven gating-based motion-corrected (“DDG-MC”). Assessment was conducted independently by two nuclear medicine specialists blinded to the reconstruction method on a six-point scale s ranging from “certainly negative” (1) to “certainly positive” (6). Differences in s between reconstruction methods, accounting for variation caused by readers, were assessed by nonparametric regression analysis of longitudinal data. From s, a dichotomous score for N1, N2, and N3 (“negative,” “positive”) and a subjective certainty score were derived. SUV and metabolic tumor volumes (MTV) were compared between reconstruction methods.ResultsBG-MC resulted in higher scores for N1 compared to static (p = 0.001), whereas DDG-MC resulted in higher scores for N2 compared to static (p = 0.016). Motion correction resulted in the migration of N1 from tumor free to metastatic on the dichotomized score, consensually for both readers, in 3/43 cases and in 2 cases for N2. SUV was significantly higher for motion-corrected PET, while MTV was significantly lower (all p < 0.003). No significant differences in the certainty scores were noted.ConclusionsPET motion correction resulted in significantly higher lymph node assessment scores of expert readers. Significant effects on quantitative PET parameters were seen; however, subjective reader certainty was not improved.