F18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) plays a crucial role in tumour diagnosis, staging, and therapy response evaluation of various cancer types and has been a standard imaging modality used in clinical oncology practice for many years. However, it has certain limitations in evaluating some particular gastrointestinal cancer types due to low FDG-avidity or interphering physiological background activity. Fibroblast activation protein (FAP), a protein of the tumour microenvironment, is overexpressed in a wide range of cancers which makes it an attractive target for both tumour imaging and therapy. Recently, FAP-targeted radiopharmaceuticals are widely used in clinical research and achieved great results in tumour imaging. Considering the limitations of FDG PET/CT and the lack of physiological FAP-targeted tracer uptake in liver and intestinal loops, gastrointestinal cancers are among the most promising indications of FAP-targeted imaging. Herein, we present a comprehensive review of FAP-targeted imaging in gastrointestinal cancers in order to clarify the current and potential future role of this class of molecules in gastrointestinal oncology.

Pancreatic ductal adenocarcinoma (PDAC) represents a formidable challenge due to its aggressive nature and poor prognosis. The tumor microenvironment (TME) in PDAC, characterized by intense stromal desmoplastic reactions and a dominant presence of cancer-associated fibroblasts (CAFs), significantly contributes to therapeutic resistance. However, within the heterogeneous CAF population, fibroblast activation protein (FAP) emerges as a promising target for Gallium-68 FAP inhibitor positron emission tomography (Ga68FAPI-PET) imaging. Notably, 68Ga-FAPI-PET demonstrates promising diagnostic sensitivity and specificity, especially in conjunction with low tracer uptake in non-tumoral tissues. Moreover, it provides valuable insights into tumor–stroma interactions, a critical aspect of PDAC tumorigenesis not adequately visualized through conventional methods. The clinical implications of this innovative imaging modality extend to its potential to reshape treatment strategies by offering a deeper understanding of the dynamic TME. However, while the potential of 68Ga-FAPI-PET is evident, ongoing correlative studies are essential to elucidate the full spectrum of CAF heterogeneity and to validate its impact on PDAC management. This article provides a comprehensive review of CAF heterogeneity in PDAC and explores the potential impact of 68Ga-FAPI-PET on disease management.

We present a 78-year-old man with suspicion of prostate cancer due to a PSA of 200 ng/mL, who underwent(18)F-PSMA-1007 (prostate specific membrane antigen) PET/CT for primary staging. Besides heterogeneous uptake to the prostate, an increased PSMA uptake in the cecum was observed, located in the thickened cecal wall with suspicion of a secondary malignancy. Colonoscopic biopsy followed by hemicolectomy confirmed the diagnosis of colon adenocarcinoma. This case demonstrates the importance of bioptic workup of suspicious findings on PSMA PET/CT, which are unlikely to be related to prostate cancer as PSMA ligand uptake is not exclusively prostate cancer specific.

Aim: The study aims to determine the physiological and pathophysiological distribution of the radiopharmaceutical (Ga⁶⁸-PSMA-617) and investigate whether there are differences in distribution according to the laboratory, histopathological and clinical findings that can affect image evaluation. Also, we aimed to determine cut-off values to distinguish physiological and pathological uptake in prostate, bone, and lymph nodes. Materials and Methods: 229 prostate cancer patients who underwent Ga⁶⁸-PSMA PET/CT at our department were retrospectively analyzed. The patients were grouped according to PET/CT results, Gleason scores, PSA values, received treatments, metastatic status and other laboratory values. The SUV values of the organs, tissues, and pathological lesions of the patients in these subgroups were compared among themselves. Results: No significant difference was detected in the physiological uptake of lymph nodes and bone between the groups. In the group with patients that received androgen deprivation therapy (ADT), the bone metastasis SUV values were found to be higher and the SUV values of the submandibular gland and renal cortex were found to be lower (Mann–Whitney U, p = 0.043; 0.004; 0.01, respectively). In the group with patients who received radiotherapy, the normal prostate tissue SUV values were determined to be higher (Mann–Whitney U, p = 0.009). The SUV values of the submandibular gland, muscle, liver, and blood pool were found to be lower in the group of patients with high serum LDH values. The cut-off SUVmax value was determined to be 6.945 (sensitivity 89.6%, specificity 98.1%) for primary prostate lesion; 4.72 for lymph node metastasis; 4.25 for bone metastasis. The serum PSA cut-off value to distinguish the negative/positive groups was found to be 1,505 (sensitivity 79.7%, specificity 77.3%). Conclusion: In conclusion, PSMA-617 demonstrates a similar biodistribution with other PSMA ligands. The physiological uptake of lymph nodes and bone which are mostly metastasized in prostate cancer, are not affected by the factors we examined. It should be kept in mind that the normal prostate tissue uptake may increase in patients receiving radiotherapy, and the physiological/pathological uptake of the organs may differ due to the changes in PSMA expression in patients receiving ADT, tumor burden, and kidney function may affect the biodistribution.

Although ^99mTc red blood cell (RBC) scintigraphy is a very specific method to differentiate a hemangioma from other hepatic masses, several cases of false-positive ^99mTc RBC scintigraphy have been previously reported throughout the literature. We report an additional case that presented in a 15-month-old boy with hepatoblastoma showing increased labeled RBC activity mimicking hemangioma.

We report the case of a 49-year-old woman with achalasia in whom thyroid stimulating hormone supression was incidentally detected on routine blood tests and who therefore underwent thyroid scintigraphy. Thyroid scan demonstrated low intensity diffuse technetium 99mTc sodium pertechnetate accumulation inferior to thyroid gland. After correlating the images with her previous barium esophagogram, tracer accumulation caudal to thyroid gland was explained on the presumption of 99mTc sodium pertechnetate retention within the dilated esophagus.