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These are PET glucose metabolic images (shown on the right) compared with X-ray computed tomography (shown on the left) of a patient with aphasia. The studies were performed at two months and four years following left hemisphere cerebral hemorrhage. Note that for both time frames, the extent of cerebral hypometabolism (less black) is much greater than the actual lesion or residual cavity (at late time). These studies demonstrate that the functional abnormality demonstrated with PET typically exceeds that seen with structural imaging techniques such as X-ray, CT, or MRI and is a more representative depiction of the underlying functional state of the brain and the resultant abnormal behaviors it produces. [Metter EJ, et al. Arch Neurol. 1980;47:1235-38.]