New Bismuth Composite Shield for Radiation Protection of Breast During Coronary CT Angiography

The main problem with coronary computed tomography angiography (CCTA) scan is the extreme exposure of patients during imaging. Bismuth belt shield is a new design to minimize the received dose in CCTA. The purpose of this study was to design and construct new bismuth-silicon composite shields to reduce the risk of ionizing radiation during CCTA, along with an examination of the diagnostic capability of the image for the physician. Dose reduction was calculated by placing thermoluminescent dosimeters (TLDs) in skin and glandular position for breast dose measuring in the multi detector CT. CCTA scans were performed with new 10% and 15% bismuth composite shields with 1 mm and 1.5 mm thicknesses. Image quality was assessed by CT numbers and noise evaluation. The breasts recorded dose without using shield were 7 - 8.90 mGy related to large or normal breasts and skin or glandular dose. The results of using 10% and 15% bismuth composite shields induced to dose reduction 9% - 31% depending on breast size, shield thickness and skin or gland position. There was a significant relationship between the reduction of breast doses and the thickness of the shields, bismuth weight percentage, the size of the breast and the dosimetry in the skin or gland. The mean noise increased from 8% to 33% in the breast position and from 4% to 25% in regions of Interest (ROIs) in locations of coronary arteries. The new belt bismuth-silicon shields have the potential to reduce breast dose by conserving image quality for acceptable diagnosis in CCTA.