The purpose of this review was to evaluate the accuracy of SPECT in acute pulmonary embolism. Sparse data are available on the accuracy of SPECT based on an objective reference test. Several investigations were reported in which the reference standard for the diagnosis of pulmonary embolism was based in part on the results of SPECT or planar ventilation-perfusion (V/Q) imaging. The sensitivity of SPECT in all but one investigation was at least 90%, and specificity also was generally at least 90%. The sensitivity of SPECT in 4 of 5 investigations was higher than that of planar V/Q imaging. The specificity of SPECT was generally higher, equal, or only somewhat lower than that of planar V/Q imaging. Most investigators reported nondiagnostic SPECT V/Q scans in no more than 3% of cases. Methods of obtaining SPECT images, methods of obtaining planar V/Q images, and the criteria for interpretation varied. The general impression is that SPECT is more advantageous than planar V/Q imaging.
