CT Bismuth Breast Shielding: Is It Time to Make Your Own Decision?

C M A d s f The advent of CT revolutionized the practice of radiology. Since its introduction 40 years ago, CT has evolved into an essential diagnostic imaging modality capable of providing detailed images of organs and tissues quickly, safely, and accurately. It has been estimated that about 68 million CT procedures were performed in 2007 in the United States [1]. The clinical applications of CT have continued to expand. With this additional utilization, there is ever-increasing radiation dose to the patient population. Consequently, CT has been thought of as an increasing source of radiation exposure [2,3]. In 2006, a National Council on Radiation Protection and Measurements [4] report on population exposure showed that Americans were exposed to 7 times s much ionizing radiation from edical procedures as had been the ase in the early 1980s. The increase as due primarily to the growth in he use of medical imaging proceures, mostly the higher utilization of T (24% of the total radiation expoure per capita). With the increasing number of T examinations, public concerns bout radiation dose as well as awareess of the potential risk keep growng. These concerns are not limited o overall body radiation exposure ut also include specific organ doses. he breast is one of the tissues that is ost sensitive to radiation exposure. ccordingly, breast shielding techiques during CT examinations have een introduced. However, the use of reast shielding has triggered a debate ver its benefit in reducing breast raiation exposure compared with its mpact on diagnostic accuracy (notaly image quality). [ We conducted a Google literaure search and found 27 scientific apers published since 1997 releant to the use of breast shielding in T. Among those, 13 studies invesigated the use of breast shielding n radiation dose reduction and mage quality [5-17]. An average eduction of radiation dose up to pproximately 57% was reported ithout affecting diagnostic accuracy although the use of bismuth breast hielding generated beam hardening nd streak artifacts). Therefore, the se of bismuth breast shielding was ecommended in routine CT examiations. Nine studies or reviews indiectly supported the use of breast hielding [18-26], while 5 studies recmmended using alternative techiques to reduce radiation to the reast or discouraged the use of breast hielding altogether [27-31]. There is no question regarding the ffectiveness of bismuth shields to reuce radiation to the breast. Concerns egarding breast shielding include an dverse effect on image quality and aborption of photons exiting the patient n their way to the detectors. The deate focuses on the impact on image uality, especially CT Hounsfield unit hanges, increasing noise as well as eam hardening and streak artifacts, ossibly compromising diagnostic acuracy. Figure 1 provides a demonstraion of the use of bismuth breast shieldng and its impact on image quality. owever, most of the published literaure shows that the effect of breast hields on image quality is unremarkble. Thus, there is an overall benefit to he use of breast shielding. Some roups have even successfully impleented policies of using bismuth reast shielding intheir routinepractice 32]. Strategies have also been develb