자동노출제어장치를 이용한 요추 측면 방사선검사 시 환자 중심 위치 변화가 선량과 화질에 미치는 영향

Effects of Dose and Image Quality according to Center Location in Lumbar Spine Lateral Radiography Using AEC Mode

The purpose of this study is to consider usefulness of using AEC mode and importance of patient center location in L-spine lateral radiography by comparing dose and image quality according to the change of patient center location with using AEC mode or not. In this study, guide wire is attached to the human body phantom’s lumbar spine and the lead ruler is attached to the bottom of the wall detector to find out center location in detector. ESD, ㎃s, and EI were selected as dose factors, and image quality was compared through SNR. With the lumbar spine located center of the detector, dose factors and image quality were compared according to using AEC mode or not. Afterwards, phantom moved 4 ㎝ and 8 ㎝ back and forth and compared dose factors and image quality. The exposure parameters were 85 ㎸p, 320 ㎃, x-ray field size 10×17 inch, and the distance between the center X-ray and the detector was fixed at 100 ㎝. The center X-ray was perpendicular to the fourth lumbar spine and the only bottom AEC chamber was used. All data were analyzed by independent t-test and ANOVA. As a result of this study, with AEC when the center is matched, ESD was 1.31±0.01 m㏉, without AEC was 2.12±0.01 m㏉. SNR was shown to be 22.81±1.83, and 23.44±1.87 respectively. When the phantom’s center moves 4 ㎝, 8 ㎝ forward, and 4 ㎝, 8 ㎝ backward, ESD were 1.09±0.004 m㏉, 0.32±0.003 m㏉, 1.19±0.017 m㏉, 1.11±0.006 m㏉ respectively, SNR were 18.29±0.60 ㏈, 11.11±0.22 ㏈, 18.98±0.80 ㏈, 17.71±0.82 ㏈. Using AEC in L-spine lateral radiography reduced ESD by 38%, EI by 35%, and ㎃s by 38%, without any difference in SNR(p<0.05). When the phantom’s center moves 4 ㎝, 8 ㎝ forward, and 4 ㎝, 8 ㎝ backward, ESD was decreasing each 16%, 75%, 9%, 15%, EI was decreasing each 14%, 77%, 15%, 20%, mAs was decreasing each 15% 75% 9%, 15%. SNR was decreasing each 19%, 51%, 17%, 22%.