Exploration the feasibility and additional value of [¹⁸F]FDG/[⁶⁸Ga]Ga-FAPI-04 dual-low-activity-tracer one-stop total-body PET imaging at 34 min post-injection of [⁶⁸Ga]Ga-FAPI-04.

Abstract

To validate the feasibility of one-stop 2-[¹⁸F]fluoro-2-deoxy-D-glucose ([¹⁸F]FDG) and [⁶⁸Ga]Ga-fibroblast activation protein inhibitor-04 ([⁶⁸Ga]Ga-FAPI-04) dual-low-activity-tracer positron emission tomography/computed tomography (PET/CT) at 34 min post-injection of [⁶⁸Ga]Ga-FAPI-04 and explore its additional value. Thirty pairs of patients with suspected malignancies who underwent dual-tracer imaging were enrolled in this retrospective study. The images were reconstructed at 34-39 and 50-60 min after additional injection of [⁶⁸Ga]Ga-FAPI-04 (in one-stop FDG-FAPI PET/CT, named PET_FDG, PET_D34-39, and PET_D50-60; in the 2-day protocol, named PET_FDG', PET_F34-39, and PET_F50-60, respectively). Tumour-to-normal ratios (TNR) of lesions in PET_FDG, PET_D34-39, and PET_D50-60 and TNR of lesions in PET_F34-39 and PET_F50-60 were evaluated separately. To evaluate the potential added value of one-stop FDG-FAPI PET/CT over the 2-day protocol, TNRs of PET_FDG, PET_D34-39, and PET_D50-60 were compared with PET_F34-39. The lesion detectability of the two imaging protocols was evaluated by chi-square test. Comparing FAPI-weighted PET (PET_D34-39 and PET_D50-60) and single-tracer imaging (PET_FDG) in one-stop FDG-FAPI PET/CT, TNRs of FAPI-weighted PET were higher than those of PET_FDG. PET_D34-39 and PET_D50-60 showed similar performance in lesion detectability and TNRs (all P > 0.05). In the 2-day protocol, there are no statistically significant differences in TNRs of all lesions at PET_F34-39 and PET_F50-60. Comparing one-stop FDG-FAPI PET/CT with the 2-day protocol, TNRs of PET_F34-39 were significantly higher than those of PET_FDG but lower than those of PET_D34-39 and PET_D50-60. Lesion detectability in the one-stop FDG-FAPI PET/CT was higher than that in the 2-day protocol. The average radiation dose in one-stop FDG-FAPI PET/CT was significantly lower than that in the 2-day protocol (P<0.001). One-stop FDG-FAPI PET/CT at 34 min could provide sufficient information to meet clinical diagnosis and showed better lesion detectability than that in the 2-day protocol.