PET/CT With [<sup>68</sup>Ga]-NOTA-FAP-2286 for Imaging of Tendon Injuries in Rat Achilles Tendon Injury Models

Tendon injuries, particularly those affecting the Achilles tendon, are common sports-related conditions that significantly impact patients' quality of life. Although existing diagnostic methods such as MRI and ultrasound are widely used, they may occasionally fail to provide accurate pathological information. This study aimed to investigate the feasibility of using [⁶⁸Ga]-NOTA-FAP-2286 positron emission tomography/computed tomography (PET/CT) imaging for assessing an experimental rat model of Achilles tendon injury. The application of [⁶⁸Ga]-NOTA-FAP-2286 PET/CT imaging demonstrated high sensitivity in detecting and precisely localizing tendon injuries, offering more comprehensive pathological insights compared to conventional imaging techniques. Fibroblast activation protein (FAP) ,a marker for activated fibroblasts, plays a crucial role in the tendon repair process. Tracer uptake started on the injured/ruptured side from the first week post modeling and peaked during the second week. These results show that FAP expression, activated by the Achilles tendon injury and rupture, reached its highest level during the second week of the repair process. By leveraging the specificity of the [⁶⁸Ga]-NOTA-FAP-2286 tracer, this novel imaging approach accurately visualizes the extent and progression of tendon injuries in the animal model.