Walsh & Hoyt: Diagnostic Techniques

CT scans can detect over 90% of brain tumors. Refinement of CT technology has resulted in faster scanning times, increased sensitivity, decreased radiation dosage, and, with the introduction of nonionic contrast media, fewer serious contrast reactions. In general, CT scanning is less costly than MR imaging and better tolerated by critically ill, poorly cooperative, or claustrophobic patients. CT is better than MR imaging in the detection of calcification, a helpful diagnostic consideration for tumors such as craniopharyngioma, oligodendroglioma, or meningioma. CT is also preferable to MR imaging in the evaluation of bony changes, including bony erosion and hyperostosis, signs that may help in the differential diagnosis of an intracranial or intraorbital mass. Furthermore, CT better delineates acute hemorrhage within a tumor. Advances in helical and spiral CT allow volumetric and dynamic imaging and can limit image acquisition time. Disadvantages of CT include overall decreased sensitivity to small and subtle brain lesions compared with MR imaging, bony artifacts, limited imaging planes, the use of ionizing radiation, and the risk of contrast reactions.