Total-body PET/CT with half-dose [⁶⁸ Ga]Ga-PSMA-11 for biochemical recurrent prostate cancer: comparable diagnostic value to short axial field-of-view PET/CT with full-dose [⁶⁸ Ga]Ga-PSMA-11

Purpose: The objective of this study was to evaluate the diagnostic performance and image quality of total-body positron emission tomography/computed tomography (PET/CT) imaging using a half-dose of [(68) Ga]Ga-prostate specific membrane antigen ([(68) Ga]Ga-PSMA) radiotracer, compared to conventional short axial field-of-view PET/CT imaging using a full dose of [(68) Ga]Ga-PSMA. Methods: This retrospective study enrolled 52 patients with biochemical recurrent (BCR) prostate cancer after radical prostatectomy who underwent total-body PET/CT with a half-dose (0.9-1.1 MBq/kg) of [(68) Ga]Ga-PSMA. These patients were matched by baseline characteristics to another 52 BCR patients after prostatectomy who underwent conventional PET/CT with a full dose (1.8-2.2 MBq/kg) of [(68) Ga]Ga-PSMA. The half-dose group was further divided into 5-min (G5) and 2-min (G2) acquisition subgroups. Image quality was assessed through subjective analysis using a 5-point scale and objective measurements of standard uptake value maximum (SUVmax), standard uptake value mean (SUVmean), background variation (BV) of the liver, blood pool, and parotid glands. Additionally, SUVmax and tumor-to-background ratio (TBR) were calculated for lesions. Results: No significant difference in subjective image quality was found between the G2 and full-dose groups (p > 0.05). PET/CT image quality was significantly higher for the G5 versus G2 (p < 0.001) and full-dose groups (p < 0.001). TBR did not differ between the G2 and full-dose groups (4.23 +/- 5.21 vs 4.22 +/- 3.97, p = 0.99). Liver BV was significantly lower for G2 versus full-dose groups (0.16 +/- 0.03 vs 0.20 +/- 0.05, p < 0.001). Conclusions: Total-body PET/CT with a half-dose [(68) Ga]Ga-PSMA yields image quality superior or comparable to that of conventional PET/CT. The utilization of total-body [(68) Ga]Ga-PSMA PET/CT meets the diagnostic demands of BCR patients, particularly those who exhibit reduced tolerance to prolonged horizontal positioning and scan durations, while simultaneously reducing radiation exposure for the subjects.