Appropriate Timing In The Use Of Breast Shields In Children Can Further Reduce MDCT Radiation Dose

"It's important for radiologists to limit dose in CT, especially to children, and especially to radiosensitive regions, such as breast tissue; and radiologists should be familiar with strategies to do this," said Donald P. Frush, MD, lead author of the study. "Two strategies are breast shielding, and the other is automatic tube current modulation (ATCM). However, the combination of the shield and ATCM may not be effective since the equipment might increase the dose to penetrate the shield," said Dr. Frush. "We wanted to see if there was a way to circumvent this and in fact there was: by placing the shields on the patient after the topogram (scout) from which the tube current would be modulated. This was tested using a GE scanner and it may not work with other scanners," he said.

Researchers performed MDCT on the chest an anthropomorphic phantom that represented a 5-year-old child. They obtained two scans in each of four sequences: without the shield, with a 2-ply bismuth shield, ATCM after placement of the shield and ATCM before placement of the shield.

The study showed that the bismuth breast shield reduced radiation dose to the breast by 26% and shielding and ATCM reduced the dose by 52%. The study also showed that multiple organ doses were lowest when the shield was placed after the scout radiograph was obtained. With this technique, image noise increased, but the images were still of good quality.

"Radiologists need to understand their equipment's ATCM before using shielding. Parents should inquire about dose reduction strategies before their child undergoes a CT scan and physicians who refer pediatric patients to radiologists should understand that research is continuing to minimize radiation dose in CT," said Dr. Frush.

The full results of this study appear in a recent issue of the American Journal of Roentgenology.