Non-malignant findings of focal ${}^{68}$Ga-FAPI-04 uptake in pancreas

${}^{68}$Ga-Labelled Fibroblast Activation Protein Inhibitor (${}^{68}$Ga-FAPI) has shown promise in tumour positron emission tomography (PET) imaging, including malignant pancreatic lesions. Here, we showed several non-malignant findings of focal ${}^{68}$Ga-FAPI-04 uptake in the pancreas which were occasionally found by PET/MR. The study aimed to investigate the reasons for the focal uptake and remind caution for the diagnosis. We retrospectively analysed imaging data of 103 patients who underwent ${}^{68}$Ga-FAPI-04 PET/MR at our institute from May 22 to July 8, 2020. Seven patients had focally elevated uptake of ${}^{68}$Ga-FAPI-04 in the pancreas; four of these underwent simultaneous ${}^{18}$F-FDG PET/CT scans. The clinical data, PET/MR imaging features, pathological, and follow-up results were further collected and analysed. The cases showed that ${}^{68}$Ga-FAPI-04 accumulation can occur in any part of the pancreas, with corresponding negative ${}^{18}$F-FDG uptake. Most lesions were small with no significant changes in CT or MR signals. The SUVmax value of ${}^{68}$Ga-FAPI-04 had a wide range of 3.1-9.1. All the pancreatic lesions were proven to be non-neoplastic by pathology confirmation or follow-up imaging. Lesions with uptake were identified including pancreatic pseudocysts, sites of prior pancreatitis, and foci of IgG 4-related disease. Though ${}^{68}$Ga-FAPI-04 demonstrates great potential for oncological diagnosis, focal ${}^{68}$Ga-FAPI-04 uptake could occur in benign pancreatic lesions and should be carefully evaluated. Fortunately, combined with MR, ${}^{68}$Ga-FAPI-04 PET/MR may potentially avoid the misdiagnosis of some pancreatic lesions. Clinical Trial Registration: NCT04554719 and NCT04605939. Registered September 13, 2020 and October 25, 2020, respectively.