Evaluation of abdominal computed radiography (CR) exposure parameters at selected hospitals in Klang Valley of Malaysia / Mohamad Zamri Mohamad Zin @ Jin

Computed Radiography (CR) system has the ability to reduce patient radiation dose compared to the conventional screen film system. However, if it is not properly handled, it may result in higher radiation dose to the patient. The objectives of this study are to compare the kVp usage and the exposure indicators recommended by the manufacturer for abdominal CR in selected hospitals with the optimum quality image produced using standard abdominal phantom. In medical imaging laboratory, abdominal phantom images are produced using several X-ray exposure parameters setting. All images are studied for noise level, contrast, resolution and the Entrance Skin Dose (ESD). The best image with high quality and lowest ESD was identified and the mean exposure parameters involved become the references value. In clinical practice, exposure parameters used for abdominal radiography were collected and analysed in three hospitals. The mean for kVp, mAs, exposure indicator and ESD were compared between hospitals and laboratory results. The use of exposure indicators were analysed and compared with the machine Manufacturer Recommended Range (MRR). The result showed that, the mean for exposure parameters to produce the best standard abdominal image quality using phantom was 75 kVp and 46.5 mAs with ESD 5.71 mGy. In clinical practices showed that variation of exposure parameters used in clinical practice was between 60 to 80 kVp and 16 to 50 mAs. The median kVp for centre A, B and C is 75, 70 and 73 with 32, 31 and 24 mAs respectively meanwhile the median ESD for centre A, B and C is 3.77, 2.71 and 2.65 mGy. More than 60% of the exposure indicators for those centres were beyond the manufacturer recommended range (MRR) value. Each hospital practices the same standard of exposure parameters but most of them used lower setting compared to the reference value. Most of radiographers used exposure parameters beyond the MRR. The different ESD in clinical practice with the reference value is due to multiple X-ray machine used which each of them has dedicated output factors.