Comparison of testing of collimator and beam alignment, focal spot size with slit camera, and tube current consistency using computed radiography and conventional screen-film systems.

Conversion to a filmless technique of physical performance testing is becoming a topic of much interest to researchers. We assessed the use of a computed radiography (CR) system with postprocessing software as an alternative tool for performing the three physical performance tests of an x-ray tube. Collimator and beam alignment, focal spot size, and milliampere second (mAs) linearity, were performed using a CR system. Results were then compared with those obtained from a conventional screen-film (SF) system. The distances of collimator misalignment measured by the SF system were decreased while peak tube voltage (kVp) was increased (mAs was fixed), whereas those measured by CR were independent of exposure level. The degrees of beam collimator misalignment measured by the CR system were not different from those measured by the SF system. The differences in focal spot dimensions measured by SF and CR systems were less than 4% for large and small focal spot size in both width and length. The mAs linearity evaluated by the SF system agreed with those evaluated by the dose measurement at 50 kVp and 4 mAs, as well as 55 kVp and 3.2 mAs, while the mAs linearity test using the CR system agreed with those using the dose measurement method for all exposure levels. In summary, a CR system could be utilized to assess the three physical performance tests of a single x-ray tube, but required more time than an SF system. Medical physicists with image processing skills were needed to perform the analyses.