The effect of respiratory gated PET/CT on SUV of lung nodules

Objective To analyze the difference of SUV between respiratory gated (RG) and nongated PET/CT scans,and to investigate the trend of SUV change in different respiratory phases.Methods Fourteen patients (6 male,8 female,age range:29 to 80 years,average age:63.7 ± 7.1 years) with pulmonary nodules who had undergone both RG and non-gated PET/CT between May 2010 to March 2011 were enrolled in the study.A total of 37 pulmonary nodules were identified.Both PET and CT gated data were divided into 6 phases.PET images were matched with CT at different respiratory phases.Each nodule was measured 7 times including gated data of 6 phases and non-gated data.The t-test,rank-sum test and Spearman correlation analysis were used.Results The SUVmax and SUVmean of RG PET/CT ( 13.69 ± 6.70 and 8.56 ±4.11,respectively) were higher than those of non-gated PET/CT ( 12.76 ± 6.74 and 7.66 ±4.00,respectively) (t =3.475,Z =- 3.661,both P ＜ 0.001 ).The two sets were correlated with each other (r =0.971 and 0.969,both P ＜ 0.05).SUVmax was the highest at phase 1 ( end of expiration) and lowest at phase 4 (end of inspiration).In non-gated scans,there were 4 nodules with SUVmax ＜ 2.5,including 1 nodule with a higher SUV of 2.52 in the RG scan than SUV of 2.13 in the non-gated scan.Conclusions SUV of lung nodules in RG scans is higher than that in non-gated scans.The highest SUVmax could be obtained at the end of expiration.RG scans might improve the detection of lung nodules with low-grade FDG uptake. Key words: Lung neoplasms ;  Tomography, emission-computed;  Tomography, X-ray computed; Deoxyglucose