Daniel AT Souza MD, Presenter: Nothing to Disclose

Kavita Gulati MD, Abstract Co-Author: Nothing to Disclose

Leticia C.S. Souza MD, Abstract Co-Author: Nothing to Disclose

Bob Liu PhD, Abstract Co-Author: Nothing to Disclose

Aaron D. Sodickson MD, PhD, Abstract Co-Author: Consultant, Siemens AG Consultant, Bayer AG

As breast tissue is often directly irradiated during abdominal CT, the aim of this study was to quantify the breast radiation dose reduction possible by using a simple method to displace the breasts above the directly exposed region of abdominal CT.

20 female patients undergoing abdominal CT consented to have OSL dosimeter dots affixed to their skin at the sternal notch and at the nipple and each of the 4 quadrants of each breast. Patients were randomized into a control group (n=11) and an intervention group (n=9) whose breasts were mechanically displaced towards the head and held in place with a radiolucent girdle-like device containing straps and buckles (Chrysalis, Meta Imaging Solutions). Routine abdominal CT scans were then performed on a 128-slice Siemens AS+ scanner using automated tube current modulation. Dosimeter readings were normalized by the mAs of the top CT image, and used as the dependent variable in linear regression models as a function of the study group, age, weight, cup size, anteroposterior and transverse diameter at the top of the scan.

The intervention group had significantly lower dosimeter readings in the lower quadrant locations (RLO: 346 vs. 751 mRad, p=0.003; RLI: 456 vs. 823 mRad, p=0.007; LLO: 267 vs. 764 mRad, p<0.001; LLI: 252 vs. 794 mRad, p<0.001, for intervention and control groups respectively) but no significant differences in doses measured at or above the nipples. Relative to the control group, breast displacement produced an average 58% dose reduction to the lower quadrants. After controlling for the other variables in the linear regression models, intervention vs. control group remained a significant predictor of dose in each of the lower quadrants.

Straightforward mechanical displacement of the breasts can significantly reduce radiation dose to the lower breasts by removing these portions of the breast from the directly irradiated region.

We describe a new method to achieve significant breast dose reduction to the lower quadrants during abdominal CT by mechanical displacement out of the plane of imaging.

Souza, D, Gulati, K, Souza, L, Liu, B, Sodickson, A, Breast Radiation Dose Reduction Achieved by Displacing the Breasts Out of the Plane of Imaging in Abdominal CT.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11001169.html