## 4 Discussion
Despite that, in the paper by [PERSON] et al., although the specificity of \({}^{68}\)Ga FAPI is worse than \({}^{18}\)F-FDG for HCC (85.71% vs. 100%), in CCA \({}^{68}\)Ga FAPI is significantly moresensitive (94.4% vs. 50%) and accurate (95.24% vs. 57.14%), with a specificity reaching 100% [30]. The lower physiological hepatic absorption of \({}^{68}\)Ga-FAPI allowed the detection of intrahepatic metastases [29; 34; 36; 37]. Furthermore, unlike \({}^{18}\)F-FDG, FAP-targeted radiopharmaceuticals are not absorbed in the gastrointestinal tract [55], contributing to better detection of peritoneal metastases [19; 29; 33; 34; 36; 37; 38]. Overall, encouraging results were obtained in the study by [PERSON] et al., showing a sensitivity of \({}^{68}\)Ga-FAPI higher than \({}^{18}\)F-FDG with a few differences in terms of specificity and accuracy [29]. A sensitivity and specificity of 100% were found by [PERSON] et al. [32]. According to their data, FAP-targeted radiopharmaceuticals are the best among currently used PET tracers. FAPI hybrid imaging presents advantages in discerning liver tumors and benign lesions, being able to overcome the limitations of conventional radiological imaging, especially in hypovascular nodules such as well-differentiated HCC. Moreover, FAP-targeted radiopharmaceuticals, being a molecular imaging method, could reflect the histopathological characteristics of the lesion. Furthermore, FAPI has great potential as a new theragnostic target in staging and detecting disease recurrence, as well as in therapeutic and prognostic evaluation of patients with hepatic tumors [32]. Another prospective pilot study by [PERSON] et al. shows high sensitivity and accuracy of \({}^{68}\)Ga-FAPI-04 in detecting malignant liver neoplasms, especially those that are poorly differentiated and have high immunohistochemical expression of FAP [35]. These characteristics were also investigated by [PERSON] et al. in a prospective study evaluating non-FDG-avid focal liver lesions. For primary lesions, the sensitivity, specificity, and accuracy were 96%, 58%, and 94%, respectively, in line with the results of the other studies examined. In semi-quantitative analysis, SUVmax and TBR of \({}^{18}\)F-FAPI in hepatic neoplasms were significantly higher than in benign non-inflammatory focal liver lesions (FLL). However, there was no significant difference in SUVmax of \({}^{18}\)F-FAPI PET between HCC lesions and inflammatory FLLs, but the TBR in HCC was significantly lower [18]. The results of this study therefore suggest that \({}^{18}\)F-FAPI could be a promising radiopharmaceutical for the differential diagnosis of benign and malignant hepatic masses with non-avidity for \({}^{18}\)F-FDG. Similarly, [PERSON], et al. sought to establish kinetic models to differentiate HCC lesions from non-HCC lesions and concluded that the SUVmax of \({}^{68}\)Ga-FAPI-04 is sufficiently effective in distinguishing healthy regions, HCC lesions and non-HCC lesions [39]. Figure 2: From [PERSON] et al., PET/CT images in a 53-year-old male patient with moderately differentiated HCC. (**A**) \({}^{68}\)Ga-FAPI-04 PET/CT revealed a strongly FAPI-avid lesion (black and white arrows, SUVmax = 7.36, TBR = 6.03) in the right lobe of the liver. (**B**) No positive finding was observed within the liver in \({}^{18}\)F-FDG PET/CT images (SUVmax = 2.36, TBR = 1.31) [31]. This review includes studies carried out on different types of cancer, including HCC and CCA [19; 34; 36; 37; 40]. [PERSON] et al. compared \({}^{68}\)Ga-FAP-2286 and \({}^{68}\)Ga-FAPI-46, confirming that they could both be a valid alternative to \({}^{18}\)F-FDG for cancer types such as gastric, pancreatic, and liver cancers [19]. In particular, \({}^{68}\)Ga-FAP-2286 is a promising FAPI derivative with improved biological properties compared to the small molecule FAPI series [56], including binding affinity and amplified receptor selectivity, due to major plasma stability and conformational rigidity. In preclinical studies, FAP-2286 demonstrated longer tumor retention than FAPI-46 [57].