The effect of the computed tomographic scanner on utilization and charges for alternative diagnostic procedures.

Monthly utilization data for four diagnostic procedures (electroencephalography, brain scintigraphy, pneumoencephalography, and cerebral angiography) over a 10-year period were collected from a neurological institute. The computed tomographic (CT) scanner was introduced in the seventh year. Its effect on the usage of the alternative procedures was examined using three measures: (a) computing pre- and post-CT average monthly usage, (b) comparing fitted curves for the pre- and post-CT periods, and (c) projecting usage had the scanner not been available. Projected charges were compared with actual charges, and the scanner was found to be charge-saving in the second and third years of its use.