Prospective\nStudy Comparing [<sup>99m</sup>Tc]Tc-DP-FAPI\nQuantitative SPECT/CT with [<sup>68</sup>Ga]Ga-FAPI-04 PET/CT in Patients\nwith Gastrointestinal Tumors

Over the past decade, [<sup>68</sup>Ga]Ga-FAPI-04 positron\nemission\ntomography (PET)/CT imaging has been widely used for the treatment\nof various tumors. However, the application of <sup>99m</sup>TC-labeled\nfibroblast activation protein inhibitors in tumors has been less studied.\nOur team previously demonstrated the safe biological distribution\nof [<sup>99m</sup>Tc]Tc-DP-FAPI in the human body. Based on this,\nthis study reports the accuracy of [<sup>99m</sup>Tc]Tc-DP-FAPI in\nthe imaging diagnosis of gastrointestinal tumors and compares it with\nthat of [<sup>68</sup>Ga]Ga-FAPI-04 to evaluate the differences. A\ntotal of 24 patients with clinically diagnosed gastrointestinal tumors\nwere prospectively included. All patients received [<sup>99m</sup>Tc]Tc-DP-FAPI quantitative SPECT/CT imaging on the first day and\n[<sup>68</sup>Ga]Ga-FAPI-04 PET/CT imaging on the second day. And\nthe effectiveness of the two imaging probes in detecting suspicious\nlesions was analyzed and compared. The primary tumors of all 24 patients\nwere well detected by two imaging probes, and the sensitivity of [<sup>99m</sup>Tc]Tc-DP-FAPI and [<sup>68</sup>Ga]Ga-FAPI-04 to the primary\nlesions was 100%. [<sup>99m</sup>Tc]Tc-DP-FAPI examined 21 lymph nodes\nwith a sensitivity and specificity of 32.8% and 10.9%, and [<sup>68</sup>Ga]Ga-FAPI-04 detected 57 lymph nodes with a sensitivity and specificity\nof 89.1% and 67.2%, respectively. Three distant metastases were detected\nby [<sup>99m</sup>Tc]Tc-DP-FAPI and nine metastases by [<sup>68</sup>Ga]Ga-FAPI-04. The study showed that [<sup>99m</sup>Tc]Tc-DP-FAPI\nis highly sensitive to detecting primary lesions of gastrointestinal\ntumors. Compared with [<sup>68</sup>Ga]Ga-FAPI-04, [<sup>99m</sup>Tc]Tc-DP-FAPI has the same sensitivity in detecting primary tumors\nbut has certain limitations in detecting metastases. [<sup>99m</sup>Tc]Tc-DP-FAPI is of great value for preliminary screening of tumor\nlesions and early diagnosis of disease in patients who are suspected\nof having gastrointestinal tumors.