부산대학교 도서관

Computed tomography (CT) has contributed about 50% of the collective dose from medical exposure. The dose from CT has been considered seriously. Thus, automatic tube current modulation is designed to reasonably lower radiation dose without affecting image quality. The purpose of this study is to evaluate how automatic tube current modulation to optimize radiation dose and to impact image quality. A standard reference anthropomorphic phantom took head, neck, chest, abdomen, pelvic, and whole abdomen (including pelvic) scanning on a multidetector CT scanner (Somatom Sensation 64, Siemens) with and without automatic tube current modulation (CARE Dose 4D, Siemens). Organ doses and effective doses were estimated by the high sensitivity and tissue-equivalent thermoluminescent dosimeters (TLD). Effective dose conversion factors were also used to fast calculate effective dose. Image quality was assessed by analyzing the noise level of images. The effective dose decreased 5~47% in head, chest, abdomen, pelvic and whole abdomen scanning after applying automatic tube current, the dose decrease in the whole abdomen scanning is most obvious (47%). However, the effective dose in the neck scanning increased 65%. Although image quality has no change (p=0.061~0.761) by using automatic tube current modulation, the image noise level increases (p＜0.001) in the part of shoulder, abdomen, and pelvic. The conclusion of this study is that automatic tube current modulation could lower 5~47% radiation doses without affecting diagnostic acceptability of images for radiologists, and achieve the requirement of reasonable dose reduction. However, automatic tube current modulation should be used carefully in order to lower, not increase radiation dose, especially in the neck scanning.