Optimization of dose and image quality for computed radiography (CR) and digital radiography (DR) for chest, abdoment and lumbar sacral spine in Pahang

Abstract

Optimization of dose in radiographic examinations is essential since the utilization of x-radiation have a related induced cancer risk. Further, the quality of images produced need to be maintained at an accepted diagnostic level. Thus, this study was conducted with the aim to provide guidance to the radiographers in ensuring best practises in producing radiographs for common radiographic examinations of acceptable image quality in digital radiography whilst minimizing radiation dose that could cause harmful effects. The study comprised of three phases. The first phase (pre optimization study) involved 90 respondents aged between 20 to 60 years and weighed between 60-80 kilograms that underwent AP abdomen, AP and lateral lumbar sacral spine and PA chest examinations. During this phase, technical parameters selected for 30 radiographs from each examination was left to the discretion of the radiographers. Kerma X_plus, DAP meter was utilized to evaluate the entrance surface dose (ESD) while CALDose_X 5.0 Monte Carlo was used to estimate effective dose. The second phase (experimental study) utilized an anthropomorphic phantom (PBU-50) and Leeds test object to compare image quality. Variation of technical parameters was utilized to find the best parameters to be adapted to patient AP thickness in the post optimization study. In the optimization study, 90 radiographs were produced with similar respondent’s characteristics as the pre optimization study but utilizing the best technical parameter from the experimental phase with the lowest ESD and acceptable image quality. The image quality for pre and post optimization were assessed by two radiologists utilizing the modified criteria from the Commission of European communities on image quality. Inferential statistics indicated there were significant differences (p<0.05) between image quality and radiation dose for PA chest in HOSHAS and HTAA in the pre optimization study. Wilcoxon signed-rank test reflected that there were significant differences in image quality for pre and post optimization study with better image quality found in the post optimization for all four examinations. However significant differences in ESD were only found for AP abdomen and PA chest with a lower ESD being received by patients in the post optimization study. Tube potential (kVp), tube current-time, focus to film distance (FFD), usage of grid, automatic exposure control, additional filter and practice of radiographers were found to be associated with image quality and radiation dose. The study also indicated that the ESD received by the patient for post optimization study to be lower than all published data and that suggested by radiation regulatory bodies. Optimization of dose and image quality was achieved from this study by proper use of AEC with correct chamber selection, utilizing an appropriate kVp, correct FFD (115cm) and the use of 0.2mm added copper filtration.