## 4 Discussion
[PERSON] et al. observed \({}^{68}\)Ga-FAPI-04 uptake in 28 types of cancer. In the semi-quantitative analysis, the highest SUVmax (>12) was found in CCA, in sarcoma, as well as breast, esophageal, and lung cancers, while an intermediate SUVmax (6-12) was found in HCC, colorectal, pancreatic, prostatic, ovarian and head-neck carcinomas. The high TBR allowed the detection of liver metastases as small as 1 cm in diameter and the identification of peritoneal carcinomas, particularly frequent in ovarian cancer. This study therefore underlines the potential of FAPI tracers for the non-invasive therapists approach to tumors [37]. A similar prospective study was carried out by [PERSON] et al., showing a greater sensitivity of \({}^{68}\)Ga-FAPI-04 compared to \({}^{18}\)F-FDG (98.2% vs. 82.1%). Lymph node uptake was also significantly higher in the neck, supraclavicular, abdomen, and mediastinum regions. Regarding metastatic lesions, SUVs derived from \({}^{68}\)Ga-FAPI were 2-3 times greater than values derived from \({}^{18}\)F-FDG. Indeed, more lesions were discovered in the regions of the liver, brain, axial skeleton, peritoneum, mesentery, and quantum, with higher sensitivity (83.8% vs. 59.5%) and accuracy (73.5% vs. 59.2%). In this study, \({}^{68}\)Ga-FAPI-04 PET-CT was able to visualize very small tumors (diameter < 1.0 cm), which were not detected by \({}^{18}\)F-FDG PET-CT. Furthermore, the study highlights the utility of the FAPI tracer in delineating gross tumor volume in preparation for external beam radiotherapy due to exceptionally clear tumor delineation and high TBR in nasopharyngeal carcinoma [34]. [PERSON] et al. compared \({}^{68}\)Ga-FAPI-04 and \({}^{18}\)F-FDG PET-CT in various oncological and non-oncological lesions. \({}^{68}\)Ga-FAPI-04 demonstrated a significantly higher uptake and detection rate for primary lesions (sensitivity 97.67 vs. 84.89%; and accuracy 96.59 vs. 82.95%), nodal metastasis (sensitivity 97.59 vs. 84.72%; and accuracy 97.34 vs. 84.31%) and distant metastasis (sensitivity 98.01 vs. 65.59%; and accuracy 97.04 vs. 65.51%) of solid tumor, while it showed a lower activity and detection rate (sensitivity 50.65 vs. 96.75% and accuracy 51.28 vs. 95.51%) for multiple myeloma and lymphoma compared to \({}^{18}\)F-FDG. As regards non-oncological lesions and benign tumors, the two radiopharmaceuticals showed comparative detection activity and efficacy (sensitivity 86.52 vs. 72.34% and accuracy 84.83 vs. 72.41%) [36]. The study by [PERSON] et al. analyzes tumors of the gastrointestinal tract, such as HCC, CCA, pancreatic cancer, colorectal cancer, and neuroendocrine tumors, comparing PET-CT with \({}^{68}\)Ga-FAPI-04 to gold-standard conventional imaging for the specific pathology. In this study, \({}^{68}\)Ga-FAPI-04 brought changes in half of patients with digestive system cancers, particularly HCC and pancreatic cancers, leading to changes in therapeutic management in 25% of these patients, identifying local and distant lesions that allowed the beginning of systemic chemotherapy [40]. There have also been studies comparing FAPI PET and FDG PET to MRI as the gold standard [33; 38]. The results suggest that \({}^{68}\)Ga-FAPI PET-CT can more accurately detect liver cancer than \({}^{18}\)F-FDG PET-CT or MRI alone [33]. Indeed, \({}^{68}\)Ga-FAPI-46 showed a favorable TBR, detecting 100% of intrahepatic tumors like MRI. In contrast, only 52% of lesions were detected with \({}^{18}\)F-FDG. The main advantage of PET-CT over MRI is the detection of extrahepatic metastases. Positive uptake rates of regional lymph node metastaseswere 100% with \({}^{68}\)Ga-FAPI-46 and 58% with \({}^{18}\)F-FDG. More distant metastatic lesions were detected with \({}^{68}\)Ga-FAPI-46 compared to \({}^{18}\)F-FDG (96% vs. 89%, respectively), with 4 peritoneal metastases and 1 brain metastasis detected with \({}^{68}\)Ga-FAPI-46 and not detectable with \({}^{18}\)F-FDG PET-CT [33]. In the same way, the sensitivity of \({}^{68}\)Ga-FAPI-04 PET-CT in the retrospective analysis by [PERSON] et al.