Method to track radiographic variables affecting image quality

摘要

Separating x-ray source fluctuations from film processing variations is a difficult task. We have established a system which monitors the performance of our film and film processing. In order to monitor consistency we have developed two devices, the ''spotburner'' and the ''flasher.'' The spotburner allows us to expose uniform small spots using a Cd-109 source over representative areas of a film. For each production film batch to be processed we use two spotburner films, one leading and one trailing the production films. To identify these films we use the flasher to mark the films with time and data. Production film batch information as well as important processor parameters are recorded in a data base for analysis and to keep a historical record. Quantitative radiography is very sensitive to film and processor variations. These variations may be brought about by many causes. One cause could be variation in the emulsion across the surface of a film. When exposing a film for quantitative analysis a stepwise of a known material is exposed along with the part to be evaluated. Any emulsion changes from the area of the stepwedge to the area of the test piece can make significant errors in perceived x-ray attenuation. A second cause of variations are fluctuations in the output of the x-ray source or changes in the flight path. A third source of film variations are processor fluctuations. Changes in developer chemistry, developer and time water temperatures, and film movement rates through the processor can all causes a shift in apparent exposure from one side of a film to the other.