Performance assessment of the scanning-beam digital x-ray (SBDX) system

A prototype scanning-beam digital x-ray (SBDX) system for cardiac fluoroscopy has been constructed. The unique geometry and absence of detected x-ray scatter in the SBDX image promises to provide image quality equivalent to a conventional image-intensifier-based fluoroscopic system at substantially reduced x-ray exposure to patient and staff. In order to measure the SBDX exposure advantage, a contrast-detail study was performed comparing SBDX and a conventional cardiac fluoroscopic system. Low-contrast detectability as a function of the phantom entrance exposure was determined. The expected SBDX exposure advantage in this experiment, with respect to the conventional system, was calculated to be 3.2. The measured exposure advantage was 3.0 to 3.4, for low-contrast objects ranging in diameter from 2 to 10 mm. This exposure advantage is applicable to the AP projection through an average-size cardiac patient. Based on these results, calculations show that angulated views and larger patients will experience significantly greater exposure reductions. In addition, the results also indicate that SBDX system design modifications can provide a greater exposure reduction from that measured with this prototype.