Added value of 18Fluorine-fluorodeoxyglucose (18F-FDG) PET/MRI for evaluation of failed back surgery syndrome: comparison with non-contrast MRI.

Objectives: Given increasing research suggesting the utility of positron emission tomography/magnetic resonance imaging (PET/MRI) in identifying the pain generator of low back pain, our study aims to assess its effectiveness in evaluating the source of pain in patients with failed back surgery syndrome (FBSS) by comparing the performance of fluorine-18-labeled fluorodeoxyglucose (¹⁸F-FDG) PET/MRI with conventional MRI.

Methods: We retrospectively analyzed data from patients with FBSS who underwent ¹⁸F-FDG PET and MRI of the lumbar vertebrae and lower extremities for undetermined sources of pain. We assessed 1) The diagnostic reliability and efficacy of MRI and ¹⁸F-FDG PET/MRI according to correct differential diagnosis, affected level, and affected side of the pain source compared to the findings of selective root or peripheral nerve block or revision lumbar spine surgery; and 2) The association between standardized uptake value (SUV) and standardized uptake value ratio (SUVR) threshold and accuracy of the suspected pathology on ¹⁸F-FDG PET/MRI.

Results: Among 30 included patients, the diagnostic accuracy of pain source recognition was higher for ¹⁸F-FDG PET/MRI than for MRI alone (1.0 vs. 0.4 in spinal disease and 0.8 vs. 0 in lower extremity disease, both p < 0.05). SUVR values of 1.4-1.5 showed the highest accuracy (0.93), higher than the accuracy obtained using the SUV threshold (0.87).

Conclusion: ¹⁸F-FDG PET/MRI added value to MRI alone in detecting of hypermetabolic activity associated with pain from spinal and non-spinal sources.