Conventional SPECT Versus 3D Thresholded SPECT Imaging in the Diagnosis of ADHD: A Retrospective Study.

Brain single photon emission CT (SPECT) scans indirectly show functional activity via measurement of regional cerebral blood flow. In conventional SPECT scans, the typical tomographic slices are produced. In three-dimensional thresholded SPECT scans, pixels representing activity below a certain threshold are discarded. A retrospective analysis of 427 patients shows that three-dimensional thresholded SPECT scans yield a sensitivity for predicting clinical attention deficit hyperactivity disorder of 54% [95% confidence interval (CI), 46%-61%; specificity, 76%; 95% CI, 71%-81%] compared with 4% sensitivity [95% CI, 2%-8%; specificity, 97%; 95% CI, 94%-98%] for conventional SPECT scans. For 170 of the patients originating from a general psychiatry practice, conventional SPECT showed 10% sensitivity (95% CI, 4%-23%) and 98% specificity (95% CI, 93%-99%), whereas three-dimensional thresholded SPECT showed 83% sensitivity (95% CI, 68%-91%) and 77% specificity (95% CI, 69%-83%). These findings indicate that a much stronger signal is obtained when the three-dimensional thresholded SPECT scan is performed rather than the conventional SPECT scan in detecting attention deficit hyperactivity disorder and suggest similar results may be obtained for other psychiatric disorders.