RT Journal Article SR Electronic T1 Optimal 68Ga-PSMA PET/CT imaging in assessment of prostate cancer: feasibility of only delayed acquisition using a total-body PET/CT scanner? JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 2544 OP 2544 VO 63 IS supplement 2 A1 Yu, Xiaofeng A1 Xu, Lian A1 Li, Jiajin A1 Wang, Ying A1 Liu, Jianjun A1 Chen, Yumei YR 2022 UL http://jnm.snmjournals.org/content/63/supplement_2/2544.abstract AB 2544 Introduction: While&nbsp;dual-time&nbsp;point&nbsp;68Ga-PSMA PET/CT could&nbsp;increase the lesion detection rate&nbsp;in PCa patients, it remains difficult to perform due to busy clinical service, the low count statistics and more radiation in delayed imaging.&nbsp;To prove that when performed on a total-body PET/CT, only one-time delayed acquisition of 68Ga-PSMA is feasible&nbsp;and&nbsp;provides increased lesion detection rate compared to standard acquisition.&nbsp;Methods: A retrospective clinical study between December 2020 and July 2021 was performed in 56 patients with PCa who had undergone 68Ga-PSMA-11 total-body PET/CT. All patients received a standard acquisition at 1 h p.i. and a late acquisition at 3 h p.i. . All images were obtained in a single bed position for 5 min on the total-body PET/CT. The image quality was qualitatively evaluated using a 5-point Likert scale. Lesions uptakes (SUVmax) and target-to-liver ratio (TLR) were compared using a Wilcoxon matched-pairs signed rank test, background uptakes (SUVmean) was compared using an Independent t test. And all lesions were further analyzed based on uptake values, sizes, types and sites.Results: A total of 56 patients (mean age, 68&nbsp;±&nbsp;7 [standard deviation]) were enrolled in this study. The image quality was qualitatively assessed as modestly lower in the delayed imaging (3.4&nbsp;±&nbsp;0.5 at 3 h p.i.&nbsp;vs 4.8&nbsp;±&nbsp;0.2 at 1 h p.i.). The delayed images showed significantly increased PSMA-avid lesion&nbsp;uptake values (SUVmax)&nbsp;(median, 11.0 [range, 2.3 ~&nbsp;193.6] vs&nbsp;7.0&nbsp;[2.0&nbsp;~&nbsp;124.3], p&nbsp;<&nbsp;0.001) and elevated TLR (median, 3.3&nbsp;[range, 0.5&nbsp;~&nbsp;62.2]&nbsp;vs&nbsp;1.7 [0.3 ~ 30.7], p&nbsp;<&nbsp;0.001) compared to the standard images.&nbsp;The delayed images&nbsp;also presented reduced&nbsp;uptake values in most of the background regions (SUVmean). Delayed images provided additional lesion detection in 14 of 56 patients (25%), impacting management plans in 8&nbsp;of the 14 patients. Late acquisitions identified 9.7% additional PSMA-avid&nbsp;lesions&nbsp;(22/226) in the pelvic and extra-pelvic regions, 13&nbsp;of these 22 additional lesions were small lymph nodes (D&nbsp;<&nbsp;10mm) with significantly higher&nbsp;SUVmax&nbsp;and TLR.Conclusions: Compared with the standard imaging, delayed imaging with 68Ga-PSMA-11 total-body PET/CT offered higher lesion uptake, reduced background uptake and improved lesion contrast. The additional findings in the delayed imaging provided a valuable information in the assessment of prostate cancer patients. The proposed protocol with only one-time acquisition of 5 min performed at 3 h p.i. is feasible in the clinical practice when performed on a total-body PET/CT system with an AFOV of 194 cm.Acknowledgement:This work was supported in part by the National Key Research&nbsp;and Development Program of China (Grant No. 2020YFA0909000), National Natural Science Foundation of China (Grant No.82102089), Construction Project of Shanghai Key&nbsp;Laboratory of Molecular Imaging (Grant No.&nbsp;18DZ2260400), and&nbsp;Shanghai Municipal Education Commission (Class II Plateau&nbsp;Disciplinary Construction Program of Medical Technology of SUMHS,&nbsp;2018&ndash;2020)