Assessment of Therapeutic Response in Pyogenic Vertebral Osteomyelitis Using ¹⁸F-FDG-PET/MRI

There is still no definite method to determine therapeutic response in pyogenic vertebral osteomyelitis (PVO). We analyzed the value of ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) for assessing therapeutic response in PVO.

This retrospective study included 53 patients (32 men and 21 women) with lumbar PVO. The results of clinical assessments for therapeutic response were divided into "Cured" (group C) and "Non-cured" (group NC). The differences in clinical and radiological features of PVO lesions between the two groups were analyzed using clinical data and simultaneous FDG-PET/magnetic resonance imaging (MRI) obtained at each clinical assessment.

Clinical assessments and FDG-PET/MRIs were performed at 41.89 ± 16.08 (21-91) days of parenteral antibiotic therapy. There were 39 patients in group C and 14 in group NC. Diagnostic accuracies (DAs) of FDG uptake intensity-based interpretation and C-reactive protein (CRP) for residual PVO were as follows (p < 0.01): 84.9% of the maximum standardized uptake value of PVO lesion (PvoSUV_max), 86.8% of ΔPvoSUV_max-NmlSUV_max (SUV_max of normal vertebra), 86.8% of ΔPvoSUV_max-NmlSUV_mean (SUV_mean of normal vertebra), and 71.7% of CRP. DAs were better (92.5-94.3%) when applying FDG uptake intensity-based interpretation and CRP together. Under the FDG uptake distribution-based interpretation, FDG uptake was significantly limited to intervertebral structures in group C (p = 0.026).

The interpretations of intensity and distribution of FDG uptake on FDG-PET are useful for detecting residual PVO in the assessment of therapeutic response of PVO. The combination of FDG-PET and CRP is expected to increase DA for detecting residual PVO.