One-Stop 68 Ga-FAPI/ 18 F-FDG Total-Body PET/CT Scan : More Theranostics Information Available.

Abstract

This prospective study aims to assess the feasibility of a one-stop imaging protocol using 68 Ga-FAPI-04/ 18 F-FDG dual-radiotracer with dual-low-activity for tumor imaging. Forty patients underwent one-stop 68 Ga-FAPI-04 PET (PET FAPI ) and dual-radiotracer PET (PET DUAL ) using a total-body PET/CT scanner with a 194-cm axial field of view. After a half-dose (0.925 MBq/kg) 68 Ga-FAPI-04 PET/CT, an additional half-dose (1.85 MBq/kg) of 18 F-FDG was administered for a 60-minute dynamic acquisition. PET DUAL was reconstructed at 10-minute intervals (PET D0-10 , PET D10-20 , PET D20-30 , PET D30-40 , PET D40-50 , and PET D50-60 ). Data of lesion detectability, target-to-background ratios, tumor staging, and total radiation dose were analyzed. A target-to-liver ratio (TLR) ≥ 3 on PET FAPI was considered indicative of sufficient fibroblast activation protein expression. PET D50-60 and PET FAPI showed similar performance in detecting primary tumors (42 vs 41, P  > 0.999). However, significantly more metastatic lesions were identified on PET D50-60 compared with PET FAPI (102 vs 60, P  < 0.001). PET FAPI demonstrated significantly higher TLR, target-to-blood-pool ratio, and target-to-normal-tissue ratio than PET DUAL ( P  < 0.05). Lesion detectability was similar across PET D10-20 , PET D20-30 , PET D30-40 , PET D40-50 , and PET D50-60 (all P 's > 0.05). Notably, PET D30-40 and PET D40-50 detected all lesions identified by PET D50-60 . PET D40-50 showed no significant differences in TLR, target-to-blood-pool ratio, and target-to-normal-tissue ratio compared with PET D50-60 ( P  > 0.05). Up to 94.9% of malignant primary lesions exhibited a TLR ≥ 3 on PET FAPI . The average effective dose was 9.85 ± 2.19 mSv, similar to that of a whole-body 18 F-FDG PET/CT. This one-stop, dual-radiotracer, dual-low-activity imaging protocol combines the strengths of 68 Ga-FAPI-04 and 18 F-FDG, offering a shorter imaging duration and reduced radiation exposure.