Respiratory-gated time-of-flight PET/CT during whole-body scan for lung lesions: feasibility in a routine clinical setting and quantitative analysis

Purpose To demonstrate the feasibility of respiratory gating during whole-body scan for lung lesions in routine 18 F-FDG PET/CT examinations using a time-of-flight (TOF)-capable scanner to determine the effect of respiratory gating on reduction of both misregistration (between CT and PET) and image blurring, and on improvement of the maximum standardized uptake value (SUVmax). Materials and methods Patients with lung lesions who received FDG PET/CT were prospectively studied. Misregistration, volume of PET ( V p), and SUVmax were compared between ungated and gated images. The difference in respiratory gating effects was compared between lesions located in the upper or middle lobes (UML) and the lower lobe (LL). The correlation between three parameters (% change in misregistration, % change in V p, and lesion size) and % change in SUVmax was analyzed. Results The study population consisted of 60 patients (37 males, 23 females; age 68 ± 12 years) with lung lesions (2.5 ± 1.7 cm). Fifty-eight out of sixty respiratory gating studies were successfully completed with a total scan time of 20.9 ± 1.9 min. Eight patients’ data were not suitable for analysis, while the remaining 50 patients’ data were analyzed. Respiratory gating reduced both misregistration by 21.4 % ( p < 0.001) and V p by 14.2 % ( p < 0.001). The SUVmax of gated images improved by 14.8 % ( p < 0.001). The % change in misregistration, V p, and SUVmax by respiratory gating tended to be larger in LL lesions than in UML lesions. The correlation with % change in SUVmax was stronger in % change in V p ( r = 0.57) than % change in misregistration ( r = 0.35). There was no statistically significant correlation between lesion size and % change in SUVmax ( r = −0.20). Conclusions Respiratory gating during whole-body scan in routine TOF PET/CT examinations is feasible and can reduce both misregistration and PET image blurring, and improve the SUVmax of lung lesions located primarily in the LL.