Tungsten-antimony breast shield reduces radiation dose to the female breast during chest CT by 43% to 73%

May 16 2005

A new custom-designed tungsten-antimony breast shield reduces radiation dose to the female breast during chest CT by 43% to 73% without compromising diagnostic image quality, say researchers from the VCU Health System, Medical College of Virginia Hospitals and Physicians, in Richmond.

For the study, the researchers constructed a tissue-equivalent female breast, referred to as a breast “phantom,” and measured the radiation dose incurred during a chest CT scan at different quadrants of the breast phantom, both with and without the use of their breast shield. They found their custom-designed breast shield effectively reduced the radiation dose delivered to different portions of the breast between 43% and 73%.

“Diagnostic chest CT is not performed to obtain diagnostic information about the breast, but rather about the lung tissue and mediastinum. The radiation dose delivered to the radiosensitive glandular tissues of the breast is an unwanted byproduct of their location. Few physicians are aware that both diagnostic chest CT and CT angiography imparts a radiation dose of 20 to 50 mGy or more to the breasts of an average-sized woman. That CT dose is roughly equivalent to 10 to 25 two-view mammograms and up to as many as 100 to 400 chest X-rays. The increasing radiation exposure from CT and its potential adverse effects are real concerns,” said Mark S. Parker, MD, lead researcher on the study.

“When CT cannot be avoided, attempts are made to reduce the level of exposure, especially in young patients and females. Radiologists typically do this by manipulating the scanning protocol by reducing the tube current, the tube voltage or the exposure time or by increasing the table increment. However, each manipulation is associated with some compromise in image quality and, potentially, diagnostic information,” said Dr. Parker.

According to the researchers, their radiation-absorbing, lead-free breast shield, which simply drapes across the patient, is lightweight, comfortable, reusable and could be used for CT angiography, as well as routine chest CT examinations. “All of our research has so far been conducted on breast and thorax tissue-equivalent phantoms. Our study is currently before the institutional review board at our institution to begin a trial on female patients. Based on the phantom studies, we are not anticipating significant image degradation. We hope to have the shield available for commercial use in the next several months,” said Dr. Parker.

Dr. Parker will present the full results of the study on May 16 during the American Roentgen Ray Society Annual Meeting in New Orleans, LA.