[18F]fluorodeoxyglucose PET/MRI for nononcological musculoskeletal indications: reference uptake values in the asymptomatic lumbar spine and example comparison to a low back pain patient

OBJECTIVE: To assess normal [18F]fluorodeoxyglucose ([18F]FDG) uptake values in lumbar spine structures on PET/MRI in patients without low back pain. METHODS: Asymptomatic adults receiving whole-body FDG PET/MRI for nononcological indications were prospectively included. Spinal structures of interest were manually annotated at each lumbar level. Maximum standardized uptake value (SUVmax) and mean SUV (SUVmean) values were extracted from ordered subset expectation maximization, block sequential regularized expectation maximization (BSREM) β450, and BSREM β300 images. The distributions of SUVmax and SUVmean values were evaluated across spinal levels and structures. We also evaluated normalization of SUV metrics with the liver and subcutaneous fat uptake values, and correlations between SUV metrics and BMI, age, and blood glucose level. RESULTS: Twenty-two patients were included for analysis. Average SUVmax on OSEM reconstructions was 2.99 (SD: 0.69) for the vertebral body and 1.95 (SD: 0.54) for the intervertebral disc. In the nervous system, SUVmax for articular, peri-articular, and ligamentous structures was lower, ranging between 1.26 and 1.62. Uptake values were significantly lower on BSREM β450 and higher on BSREM β300. There was a positive correlation between uptake values and BMI, but no correlation was found with age or blood glucose level. CONCLUSION: Normal uptake values in the lumbar spine on [18F]FDG PET/MRI in asymptomatic adults were assessed. The uptake values reported in this study could serve as a reference for the identification of abnormalities in patients with chronic low back pain, but the applied PET reconstruction method and patient BMI should be taken into account.