Localizing pain with PET/MR

The number of people who suffer from pain is striking. The Institute of Medicine (IOM) reports that over 100 million adults in the US have chronic pain, while worldwide, 1.5 billion individuals suffer from pain related to cancer treatment and other conditions. As doctors and patients look for ways to address pain beyond the use of prescription medications, the work of Dr. Sandip Biswal, Associate Professor of Radiology (Musculoskeletal Imaging) at the Stanford University Medical Center, becomes all the more pertinent.

Dr. Biswal and his team have been developing clinical imaging methods to objectively pinpoint the site of pain generation using novel agents that specifically seek out molecular and cellular pain markers to highlight hypersensitive pain-sensing nerves.

Two recent studies led by Dr. Biswal highlight the use of PET/MR in localizing pain. In the first study using the SIGNA™ PET/MR, Dr. Biswal studied the feasibility of using an ¹⁸F-FDG PET/MR approach for improved diagnosis of chronic sciatica. In the study of nine patients with chronic sciatica and five healthy control volunteers, significantly increased ¹⁸F-FDG uptake was observed in detected lesions in all patients and was correlated with pain symptoms. ¹⁸F-FDG-avid lesions not only were found in impinged spinal nerves but also were associated with non-spinal causes of pain, such as facet joint degeneration, pars defect or presumed scar neuroma.

The second study focused on localizing knee pain in a 50-year-old patient. In the study, the patient’s chronic knee pain was resolved by removal of an intraarticular synovial lipoma, which had shown increased uptake of the novel, Sigma-1 receptor specific radioligand ¹⁸F-FTC-146 on simultaneous PET/MR. It was noted that the patient had previously undergone a variety of unsuccessful orthopedic surgeries and denervating interventions. The study illustrated the promising application of ¹⁸F-FTC-146 PET/MR as an improvement over MR alone as an imaging modality for detecting pain generators.

Further studies to validate using PET/MR to localize pain could potentially facilitate, among other things, more intelligent management of chronic pain.