Central nervous system imaging. When is CT more appropriate than MRI?

Over the past 25 years, the development of noninvasive imaging techniques has allowed exquisite display of the anatomic structures of the brain and spinal cord in normal and disease states. CT remains useful because of short imaging times, widespread availability, ease of access, sensitive detection of calcification and hemorrhage, and resolution of bony detail. MRI offers superior soft-tissue contrast, excellent visualization of vascular structures, fewer artifacts, and imaging in any plane. Cost and use of ionizing radiation are considerations in choosing the most appropriate procedure. In the future, CT and MRI applications that concentrate on functional and physiologic display of the CNS will add greatly to the clinical utility of these imaging tools.