RT Journal Article SR Electronic T1 Quantitative parametric imaging added diagnostic values in lesion detection of 68Ga-PSMA-11 in prostate cancer patients identified by dynamic total-body PET/CT JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 2584 OP 2584 VO 63 IS supplement 2 A1 Ruohua Chen A1 Yee Ling Ng A1 Haitao Zhao A1 Qi Ge A1 Fuxiao Shi A1 Kaiyi Cao A1 Yun Zhou A1 Jianjun Liu YR 2022 UL http://jnm.snmjournals.org/content/63/supplement_2/2584.abstract AB 2584 Introduction: 68Ga-PSMA-11 PET/CT has been widely used in prostate cancer primary staging and biochemical relapse. Although the semiquantitative evaluation method by standardized uptake value (SUV) has been predominantly employed to measure the PSMA avidity in clinical practices, it is susceptible to biologic and technologic factors like patient’s body weight and interscanner variability. Conventional PET scanners faced several limitations to achieve a high-quality parametric imaging, including low signal-to-noise ratio due to limited temporal resolution and sensitivity, as well as short axial field of view (AFOV). In this study, we sought to perform the total-body kinetic modeling and to explore the values of parametric imaging-based quantitative analysis by total-body 68Ga-PSMA-11 PET/CT in prostate cancer patients compared to the semiquantitative SUV method. Methods: Dynamic total-body 68Ga-PSMA-11 PET/CT scans were acquired from ten prostate cancer patients using uEXPLORER PET/CT scanner. Data were acquired for 60 minutes post-injection and reconstructed into 92 frames by the following acquisition protocol: 30 × 2 s, 12 × 5 s, 6 × 10 s, 4 × 30 s, 25 × 60 s, and 15 × 120 s. Manual delineation of volume-of-interests (VOIs) on multiple normal organs and pathological lesions was performed using PMOD software (version 4.206). Image derived input function (IDIF) method was employed to extract the blood pool from descending aorta for the total-body kinetic modelling. An irreversible two-tissue compartment model (2T3k) was fitted for each tissue time-to-activity curve (TAC) and the net influx constant (Ki) was obtained. Lesion-to-background ratio (LBR) of lesion uptake measured by kinetic parameter, Ki and SUV were also evaluated with bone (LBRBone) and muscle (LBRMuscle) used as background tissues. Results were expressed as median±interquartile range. The correlations between SUVmean/max and Ki were analyzed by Spearman’s correlation coefficient analysis. All statistical analyses were performed using SPSS 25 for Windows (IBM Corp, Armonk, NY). A p-value < 0.05 was considered statistically significant. Results: We analyzed a total of 39 lesions comprising 7 primary prostate tumors (PT), 14 lymph node metastases (LNM) and 18 bone metastases (BM). Parameters K1, k2, k3 and net influx rate constant Ki were derived from compartmental modelling. Spearman’s analysis revealed a strong correlation between Ki and SUVmean (R = 0.9 in normal organs, R = 0.92 in pathological lesions) and Ki and SUVmax (R = 0.87 in normal organs, R = 0.86 in pathological lesions) (all p < 0.001). For LBRBone, Ki of PT (153.73±117.89), LMN (112.16±77.61) and BM (76.96±30.91) revealed remarkably higher ratio than both SUVmean (81.47±39.40, 49.38±22.18, 52.56±23.47) and SUVmax (28.23±18.86, 12.56±7.99, 12.52±10.65) of PT, LMN and BM, respectively. Similar trend was observed in LBRMuscle where Ki of PT (38.9±27.44), LMN (27.06±22.27) and BM (23.72±9.43) showed notably greater ratio compared to SUVmean (28.27±18.48, 18.11±8.41, 19.45±8.02) and SUVmax (19.23±8.58, 7.76±6.76, 7.84±4.28) of PT, LMN and BM, respectively. All 39 lesions detected on 68Ga-PSMA PET/CT 60 min p.i. were all able to be visually identified by Ki parametric imaging. It is noteworthy that Ki imaging detected additional 14 lesions (8 LNM and 6 BM) that were missed detected by the conventional SUV method due to the low SUV intensity of PSMA uptake. Parametric imaging of Ki demonstrated an improved lesion visualization and detectability compared to SUVbw, especially on small-sized lesions (less than 5mm) like LNM and BM. Conclusions: Parametric images of net influx rate Ki showed enhanced lesion contrast over SUVbw and precisely led to improved visibility of lesions and metastases detection in the total-body manner, not limited to the pelvic region. Quantification using parametric imaging may serve as a non-invasive, valuable and high-accuracy diagnostic tool that added values to precision diagnosis in clinical practices.