Use of computed tomography-single-photon emission computed tomography fusion for diagnosing painful facet arthropathy. Technical note.

Facet disease is believed to play a major role in axial low-back pain and may prove in the future to be an important indication for posterior dynamic stabilization. However, the lack of good diagnostic tests and imaging methods for identifying this condition have made this entity obscure. Although single-photon emission computed tomography (SPECT) imaging is a highly sensitive and specific test, the images frequently lack adequate resolution, whereas computed tomography (CT) provides excellent resolution but lacks specificity. Thirty-seven patients with back pain clinically attributable to facet disease underwent CT-SPECT fusion imaging of the lumbar spine. The SPECT images were obtained using a dual-head gamma camera equipped with VXGP high-resolution collimators using a 20% energy window centered at 140 keV and a 360 degrees rotation totaling 128 projections at 16 seconds each. Transaxial CT images were transferred in the Digital Imaging and Communications in Medicine format to provide proper image overlay in the axial, sagittal, and coronal planes. Scanning for both modalities was performed using standard patient positioning. Patients with concordant images and symptoms then underwent joint injection and/or rhizotomy, which was performed by an independent physician. Image fusion was successfully performed in all patients, and the image quality allowed definitive localization of the "hot" lesion in all cases, in contrast to conventional high-resolution SPECT scanning, which often led to problems differentiating L4/5 and L5/S1. In patients with solitary lesions, injection led to definitive pain resolution, even if temporary, in all cases with anesthetic blockade. The CT-SPECT scanning modality combines the virtues of functional and anatomical imaging, aiding the clinician in making the diagnosis of painful facet arthropathy. This modality may prove useful for the selection of patients who are candidates for posterior dynamic stabilization.