Assessing the effects of aging on the spine using FDG-PET with novel quantitative techniques of global assessment

Objectives: ¹⁸F-fludeoxyglucose (FDG) activity reflects glucose uptake as a surrogate for active glycolysis. Regarding musculoskeletal systems, abnormally elevated FDG uptake can indicate inflammation. Regarding back pain in older populations, there is a need to understand changes in the spine during the aging process. This study examines FDG uptake in order to quantify inflammation in the spine.

Methods: A retrospective study was performed on whole-body PET scans of 19 male healthy subjects. Nine subjects were between 60 and 75 years of age (mean = 64) while ten subjects were between 22 and 54 years of age (mean = 32). The subjects were scanned 90 minutes after intravenous administration of FDG using a time-of-flight PET/CT machine. Landmarks on the CT scan were used to isolate the L5 to C1 region of the spine. All vertebral bodies and intervertebral discs including spinal processes were included in the isolated spinal region. Regions of interest (ROI) limited to the whole spinal region were created with the fused PET/CT image. The mean global standardized uptake value (global SUVmean) was calculated for each subject, and a two-sample t test was performed.

Results: The younger subjects had an average global SUVmean of 1.39, while the older subjects had one of 1.52. The global SUVmean increased slightly with subject age, but there was no significant difference between the FDG uptake in the older and younger populations (b = 0.0002, R^2 = 0.0004, P = 0.1562).

Conclusion: The uniformity of FDG uptake with age reflects the nature of inflammation in the spine during the aging process. These results show that inflammation does not significantly change with age. Alternative etiologies, apart from inflammation, must be examined to discover more robust methods of evaluating and quantifying age-related spinal disorders. Research Support: CAMONA study (NCT01724749)