Correlation of 18F-FDG PET/CT uptake with severity of MRI findings and epidural steroid injection sites in patients with symptomatic degenerative disease of the lumbar spine: a retrospective study

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PURPOSEWe aimed to retrospectively correlate 18F-fluorodeoxyglucose (18F-FDG) metabolic activitywith lumbar spine magnetic resonance imaging (MRI) findings and epidural steroid injectionsites in patients with symptomatic degenerative disease of the lumbar spine.METHODSA database search was conducted for patients receiving epidural injections <12 months aftera positron emission tomography/computed tomography (PET/CT). Maximum standard uptake values (SUVmax) were measured at the facet joints, neural foramina, and spinal canal.Severity of facet arthrosis, disc degeneration, neuroforaminal, and canal stenosis was determined on MRI using previously described grading scales. Spearman rank coefficient assessedassociation between PET/CT FDG uptake and severity of MRI findings. The SUVmax was alsocompared with injection sites.RESULTSTwenty-five patients were included, comprising MRI (n=19) and injection (n=22 patients; 18interlaminar, 8 transforaminal) groups. Injections were performed an average of 2.6 monthsafter PET/CT. The greatest SUVmax occurred at the L5-S1 spinal canal (mean SUVmax = 2.25).A statistically significant, positive correlation between uptake and grade of spinal canal stenosis was seen only at L4-L5 (r=0.60, p = 0.007). No other significant association was foundwith spinal canal or neuroforaminal stenosis, or grade of facet joint or disc degeneration. Allpatients reported symptomatic improvement after injections with mean pain score improvement of 4.4 on a 10-point scale (SD, 2.9). There was moderate agreement between sites ofepidural injection and highest SUVmax (κ= 0.591, p < 0.001).CONCLUSION18F-FDG metabolic activity on PET/CT corresponds with MRI findings about the lumbar spinal column, but there is no significant correlation between severity of MRI findings and radiotracer uptake. Given the moderate agreement between metabolic activity and levels ofsymptomatic spinal stenosis, further studies are warranted to fully evaluate the diagnosticpotential of FDG PET/CT as a surrogate for guiding epidural injections.