18F-FDG-PET/CT better localizes active spinal infection than MRI for successful minimally invasive surgery.

BACKGROUND: Surgical debridement is often required to treat spinal infections. Successful surgery requires accurate localization of the active infections, however, current imaging technique still requires surgeons' experience to narrow the surgical fields to achieve less invasive procedures.

PURPOSE: To investigate the use of F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for successful surgical planning.

MATERIAL AND METHODS: Nine patients with suspected spinal infection underwent magnetic resonance imaging (MRI) and FDG-PET/CT before surgery to locate active foci of infections. The spinal structures were divided into seven compartments at each intervertebral disc level for a total of 315 compartments investigated. The same classification system was used to design operating fields for histological correlation.

RESULTS: FDG-PET/CT diagnosed fewer compartments as active infection (34 compartments, 10.8%) than MRI (62 compartments, 19.7%, P  = 0.002). Surgical exploration was performed in 49 compartments, and demonstrated active infection in 25 compartments. The sensitivity / specificity of FDG-PET/CT was 100% / 79%, respectively, which was superior to those of MRI, 76% / 42%. Foci of active infection showed hypermetabolic activity with a SUVmax of 7.1 ± 2.6 (range, 3.0-12.7). Receiver operating characteristic (ROC) analysis indicated an optimal threshold for active spinal infection at a SUVmax of 4.2, corresponding to a sensitivity of 90.3% and specificity of 91.2%.

CONCLUSION: FDG-PET/CT demonstrated limited areas of abnormality allowing accurate delineation, and is thus useful to narrow the surgical fields. Since overall diagnostic accuracy of FDG-PET/CT was superior to that of MRI, FDG-PET/CT is a useful technique to narrow the surgical field for successful less invasive surgery.