Which method is NOT typically used in pain diagnosis?

Therapeutic ultrasound is primarily a treatment modality rather than a diagnostic tool. It is used to alleviate pain and promote healing in various conditions by applying sound waves to the affected area to reduce inflammation and improve tissue repair. In contrast, MRI, discography, and bone scans are established diagnostic techniques used to visualize structures in the body and assess the underlying causes of pain. MRI provides detailed images of soft tissues, discography involves the injection of contrast into the spinal discs to investigate disc-related pain, and bone scans are useful in detecting abnormalities in bone metabolism, such as inflammation, infection, or tumors. Therefore, therapeutic ultrasound stands apart as a method focused on treatment rather than diagnosis.