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Performance evaluation of equipment for computed tomography (CT) involves the integration of: (a) establishing performance criteria; (b) designing and implementing test procedures; and (c) reconciling test results in terms of desired performance. Precision (noise), contrast scale, linearity, accuracy, spatial independence, spatial resolution, artifacts, reproducible performance, and patient exposure are several parameters discussed, as are problems of measurement with regard to non-water bath scanners. Performance and quality control tests for the ACTA, Delta, and EMI scanners are outlined. Guidance for the prospective purchaser of CT equipment is presented as a summary of the ideas discussed.

Accurate dose prediction for megavoltage photon therapy of carcinoma of the esophagus requires information on tumor depth, lung thickness, and lung density. The authors found that CT localization of internal and external contours is accurate within +/- 1 mm. Lung density can be measured with an error of less than 0.02 g/cm3 in the range 0.25-1.00 g/cm3. Variance between predicted and measured dosage was less than 3% in all patients and in most RANDO phantom measurements. Accurate radiation therapy planning is possible with CT information from a commercial scanner.