Using the novel FAPI probe 99mTc-HYNIC-FAPI-04 and quantitative SPECT/CT imaging technology, this study investigates the diagnostic efficacy of 99mTc-HYNIC-FAPI-04 quantitative SPECT/CT in patients with common solitary bone lesions in adults, and compares its diagnostic performance with conventional CT, MRI, and 99mTc-MDP bone scintigraphy. Follow-up pathological results of patients post-surgery were analysed to assess the accuracy of 99mTc-HYNIC-FAPI-04 diagnostic outcomes, and its diagnostic value and significance were evaluated.