Guide to CAT scanning in hospital psychiatry. Overview of clinical practice and criteria for use.

Advances in imaging techniques have resulted in increasing use of computed axial tomography (CAT) in clinical psychiatry. Treatable brain lesions predominantly manifesting as emotional and behavioral symptoms can be detected with relative ease and safety by CAT scanning. Criteria to select these high-risk psychiatric patients for CAT exam are vague and sparse compared to more abundant guidelines for scanning neurologic and medical patients with focal signs of physical abnormality. The few existing surveys of inpatient psychiatry CAT scanning reveal a 65-70% range of normal findings. As more and more patients are scanned, such an obviously large group of "normals" should not be exposed to current CAT exam costs and risks; at the same time, it is necessary to ensure that those psychiatric patients warranting the procedure are not neglected in referral. This article highlights clinical aspects of CAT brain imaging, summarizes the existing literature on inpatient psychiatry CAT scanning, and recommends initial criteria for CAT brain examination of hospitalized patients.