One-Stop 68Ga-FAPI/18F-FDG Total-Body PET/CT Scan

Purpose: 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. Patients and Methods: 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. Results: 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. Conclusions: 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.