Optimization of radiation dose and image quality in abdominal radiography using digital mobile x-ray system

Abstract

The purpose of this study was to optimize the radiation dose and image quality for abdominal radiography using digital mobile x-ray system in anthropomorphic phantom at King Chulalongkorn Memorial Hospital (KCMH). Digital mobile x-ray system model OptimaXR220amx, and the Kyoto Kagaku phantom model PBU-60 with 21 cm of abdominal thickness were used. The exposure parameters were set between 70-90 kVp, and 3.2, 6.3, 12.5, 25, and 32 mAs. Source to image receptor distance (SID) was set at 100 cm. The entrance surface air kerma (ESAK) in experimental and routine parameters were measured using ionization chamber (IC) dosimeter manufactured Radcal model ACCU-Gold. The qualitative image quality criteria based on IAEA protocol and qualitative were scored by three observers. The signal-to-noise ratio (SNR) was measured by placing three regions of interest at liver, transvers process at 4th lumbar spine, and pelvis respectively. The contrast-to-noise ratio (CNR) was evaluated on three areas at liver, left kidney and transverse process at 4th lumbar spine, right kidney and pelvis. We found that the optimal parameter for 21 cm thickness of abdomen at 100 cm SID was 80 kVp, 6.3 mAs with the exposure index of 381. The average image quality and qualitative noise scoring from three observers were 5.67 and 1, respectively. The average SNR in 1st, 2nd, and 3rd ROIs were 39.56, 61.55, and 18.24, respectively, and the average of CNR at 1st, 2nd, and 3rd areas were 5.97, 7.27, and 1.50, respectively. The ESAK obtained from optimal parameter was lower than 77% compared to the routine clinical parameter. The optimal exposure parameters in this study, however, can maintain the image quality with acceptable diagnosis for portable abdominal radiography.