Comparison Between Tc-99m WBC SPECT/CT and MRI for the Diagnosis of Biopsy-proven Diabetic Foot Osteomyelitis

Magnetic resonance imaging (MRI) is the recommended diagnostic imaging technique for diabetic foot osteomyelitis (DFO), with a reported accuracy of 79%. The gold standard to diagnose osteomyelitis is bone biopsy, with a positive culture and/or histopathology findings consistent with osteomyelitis. The purposes of this study are to assess the accuracy of technetium-99m (Tc-99m) labeled white blood cell (WBC) single-photon emission computed tomography/computed tomography (SPECT/CT) hybrid imaging for diagnosing DFO confirmed by bone biopsy and to compare that to the diagnostic accuracy of an MRI. The authors performed a retrospective chart review of 166 patients who received a bone biopsy to confirm the diagnosis of a suspected DFO at a large municipal hospital between 2010 and 2013. Patients were selected on the basis of whether they received an MRI or a SPECT/CT. Patients whose scans were not within a clinically relevant time frame of the biopsy were excluded. Imaging results were correlated with probability of osteomyelitis determined by bone biopsy. For inclusion criteria, 110 patients met the study's criteria: 52 SPECT/CT patients and 58 MRI patients. The sensitivity, specificity, positive predictive value, and negative predictive value of SPECT/CT were 89%, 35%, 74%, and 60%, respectively; the corresponding values for MRI were 87%, 37%, 74%, and 58%, respectively. There were no significant differences in accuracy of diagnosing DFO between imaging techniques. This data suggests that the diagnostic accuracy of SPECT/CT imaging in DFOs is similar to an MRI.