Wet Reading

Diagnostic Imaging eNewsletter

April 2009 - Vol. 6, No. 1

CT Radiation Doses Lowered With Bismuth Shields

While CT scanning has become an indispensable tool in the diagnosis and management of numerous health conditions, it is also responsible for nearly 2/3 of the radiation exposure the public receives from medical sources. Some of the more radiosensitive organs are the thyroid gland and female breast (carcinogenetic potential) as well as the lens of the eye (risk of cataract development). Radiation shields made of bismuth have been developed which, when placed over the at risk structure during CT imaging, can reduce organ specific doses by between 50% and 60% without appreciably compromising image quality.

At NCH we recently started using these bismuth shields on all patients under age 60 years when the ordered CT examination involves direct exposure to the aforementioned organs. Age 60 was chosen because susceptibility to the deleterious effects of ionizing radiation decreases with age and any adverse event may take decades to manifest. To our knowledge, we are the only regional imaging facility to be routinely providing this protection.

Bismuth shield placed over the lower neck to protect the thyroid gland during neck and chest CT.

Contrast-infused CT image shows the bismuth shield (arrows) anteriorly. No appreciable loss in image quality is evident, but the radiation dose delivered to the underlying thyroid gland has been reduced by at least half.