Assessment of beam characteristics of some X-ray units at Security Forces Hospital and their applications in pediatric dose calculation

Abstract

Medical X-ray examinations play an important role in the diagnosing of many diseases; this benefit of X-ray is usually associated with different kinds of risks. These risks are heightened for pediatric patients, who are more radiosensitive than adults. Therefore, to keep radiation dose to a minimum, one must know the dose associated with each X-ray examination. The aims of the current work were to assess the performance of X-ray machine at Security Forces Hospital (SFH) at Riyadh, and use their beam characteristics and exposure factors to estimate entrance skin dose (ESD) of pediatric patients. The Saudi Quality control protocol developed by Dr.Outif, was conducted in the current work to assess the performance of X-ray machines at SFH. Eight X-ray machines were assessed in the current work. X-ray beam alignment, accuracy and reproducibility of kVp and exposure time, consistency of tube output with (kVp and mAs (linearity)), HVL check and Automatic Exposure Control (AEC) system tests were performed on each X-ray machine. Survey of patients' dose was then conducted on all X-ray machines that passed most of the QC tests. The beam characteristics of different X-ray machines together with the used exposure parameters were then used to estimate ESD of age groups (0-1, 1-5, 5-10 and 10-15 years old). The ESD was estimated using mathematical equations. Out of the eight machines tested in the current work, three failed most of the QC tests and therefore were not included in the patient’s survey. The remaining X-ray machines were employed in patient’s survey. Pediatric doses were found, in general, to be less than that published or recommended in other countries. Only chest AP/LAT, abdomen AP and skull AP tests yielded higher doses, which (in most cases) due to high applied mAs, low kVp and the fact that our pediatric patients have slightly higher weight compared to other countries. Most of the X-ray machines inspected in the current work failed one or more of the QC tests and this indicates the need to implement X-ray QC program in different hospitals. The high dose level found in some of the X-ray tests together with the high dose range indicates the potential to a further decrease in patient dose by the implementation of better exposure parameters and use of AEC.