SIMULATED DOSE REDUCTION IN CONVENTIONAL CHEST CT - VALIDATION-STUDY

PURPOSE: To validate a technique of computer-simulated dose reduction for conventional chest computed tomography (CT). MATERIALS AND METHODS : In 27 patients, CT scans were obtained at 200, 100, and 40 mAs at tw o levels. The raw data from the 200-mAs scan were modified on a comput er workstation to simulate the increased noise present on 100-and 40-m As scans. Real and simulated 100- and 40-mAs images were independently assessed in random order for overall image quality and radiologic fin dings by four subspecialty-trained chest radiologists who were blinded to the technique. The four observers were given paired real and simul ated images. They were asked to identify the real image and note any d ifference in diagnostic quality. RESULTS: No difference was seen in ov erall image quality or radiologic findings between real and simulated images (P > .05). In the paired comparison, 433 of 864 (50.1%) real im ages were correctly identified. CONCLUSION: Computer modification of 2 00-mAs raw scan data to simulate 100- and 40-mAs noise levels produces reconstructed images indistinguishable from real 100- and 40-mAs scan s. This technique provides realistic reduced-dose images without patie nt radiation exposure and with identical image registration and motion artifact.