Program Information
Patient Eye-Lens Dose Reduction in Routine Brain CT Examinations Using Organ-Based Tube Current Modulation and In-Plane Bismuth Shielding
Hui-Yu Tsai1, 2*, Ying-Lan Liao1, 2 , Nan-Ku Lai3, 4 , Jun-Rong Chen2 , Tou-Rong Chen3, 4 , (1) Chang Gung University, Taoyun, Taiwan, (2) Chang Gung University / Chang Gung Memorial Hospital, Taoyun, Taiwan, (3) Chung Shan Medical University Hospital, Taichung, Taiwan, (4) Chung Shan Medical University, Taichung, Taiwan
Presentations
MO-FG-CAMPUS-I-14 (Monday, July 13, 2015) 5:30 PM - 6:00 PM Room: Exhibit Hall
Purpose:
The purpose of this study is to assess eye-lens dose for patients who underwent brain CT examinations using two dose reduction methods: organ-based tube current modulation (OBTCM) and in-plane bismuth shielding method.
Methods:
This study received institutional review board approval; written informed consent to participate was obtained from all patients. Ninety patients who underwent the routine brain CT examination were randomly assigned to three groups, ie. routine, OBTCM, and bismuth shield. The OBTCM technique reduced the tube current when the X-ray tube rotates in front of patients’ eye-lens region. The patients in the bismuth shield group were covered one-ply bismuth shield in the eyes’ region. Eye-lens doses were measured using TLD-100H chips and the total effective doses were calculated using CT-Expo according to the CT scanning parameters. The surface doses for patients at off-center positions were assessed to evaluate the off-centering effect.
Results:
Phantom measurements indicates that OBTCM technique could reduced by 26% to 28% of the surface dose to the eye lens, and increased by 25% of the surface dose at the opposed incident direction at the angle of 180°. Patients’ eye-lens doses were reduced 16.9% and 30.5% dose of bismuth shield scan and OBTCM scan, respectively compared to the routine scan. The eye-lens doses were apparently increased when the table position was lower than isocenter.
Conclusion:
Reducing the dose to the radiosensitive organs, such as eye lens, during routine brain CT examinations could lower the radiation risks. The OBTCM technique and in-plane bismuth shielding could be used to reduce the eye-lens dose. The eye-lens dose could be effectively reduced using OBTCM scan without interfering the diagnostic image quality. Patient position relative the CT gantry also affects the dose level of the eye lens.
Funding Support, Disclosures, and Conflict of Interest: This study was supported by the grants from the Ministry of Science and Technology of Taiwan (MOST103-2314-B-182-009-MY2), and Chang Gung Memorial Hospital (CMRPD1C0682).
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