Evaluation Of Respiratory Motion-Corrected Pet/Ct In Lung Cancer Patients According To Tumor Location, Size, And Emphysema Status

1480 Objectives: Respiratory motions during PET acquisition can lead to blurring in PET/CT images, resulting in lower detectability of lesions and inaccurate SUV measurement. The motion correction method Q.Freeze (QF, based on 4D phase-matched PET/CT) is expected to overcome these problems. The aim of this study was to clarify the characteristics of QF compared with the non-respiratory gated images in the clinical images according to the tumor location, size, and the state of emphysema.\n Methods: 18F-FDG PET/CT scans of 58 patients (females13 and males 45, median age 73, range 45-89 years old) with primary lung cancers were acquired on a Discovery IQ PET/CT system (GE Healthcare) for 1) 2.5 min under free breathing (FB), 2) 5 min using QF per bed. Scans were started at 1 hour after administration of FDG. The images were reconstructed using a conventional OSEM algorism VUE Point. The parameters of SUVmax, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of tumors were measured on images of FB and QF. The tumors were divided into two groups in three ways 1) the upper and lower groups (n=27 and 31, respectively); tumors located above and below the tracheal bifurcation, 2) the small and large groups (n=17 and 41, respectively); tumor size of ≤ 2 cm and \u003e2cm, 3) the emphysema and non-emphysema groups (n=18 and 40, respectively); a case with emphysematous change spreading below the tracheal bifurcation was categorized into the emphysema group. The percentage differences between QF to FB in SUVmax, MTV, and TLG were calculated as percentage increase of QF in comparison with FB. The PET parameters and their percentage differences between QF to FB were compared using Mann Whitney’s U test.\n Results: QF showed significantly higher SUVmax and TLG than FB (11.4±7.1 vs 11.0±6.9, p=0.03 and 129216±230649 vs 122997±228106, p\u003c0.01), while no significant difference was observed in MTV between FB and QF (14.0±21.8 vs 13.8±20.6, p=0.22). The small group showed significantly larger percentage differences (between QF to FB) in MTV and TLG than the large group (26.9±8.3 % vs 2.1±17.3 %, p\u003c0.01, and 27.5±23.0 % vs 10.9±17.7 %, p=0.01, respectively), but not in SUVmax (3.9±21.2 % vs 7.8±25.1, p=0.32). The lower group tended to show larger percentage differences in SUVmax and TLG than the upper group (3.3±10.8 % vs 9.5±31.1 %, NS, and 11.7±16.6 % vs 17.6±22.7 %, NS, for upper and lower, respectively). The non-emphysema group tended to show larger percentage differences in MTV than emphysema group, but not significant (3.9±21.0 % vs 9.8±24.1 %, NS, for emphysema and non-emphysema, respectively).\n Conclusions: We clarified characteristics of QF in PET images for lung cancers; overall, QF showed higher SUVmax and TLG than FB. Small tumors were more influenced than large tumors by QF. Tumors in the lower location tended to show higher SUVmax and TLG with QF than with FB. The tumor in emphysematous background tended to be less affected by respiratory motion.