Determination of depth for electron breast boosts.

A technique has been developed to determine the depth for the electron boost treatments for patients undergoing definitive irradiation for early stage breast cancer. A series of parallel link chains are placed on the breast over the clinically determined site of the boost. Using fluoroscopy, the physician confirms that the chains overlie the tumor bed which is outlined by radiopaque surgical clips placed at the time of the breast biopsy. A pair of orthogonal films and/or rotational stereo shift films are obtained with a standard simulator unit. Using the image of the chains to define the surface contour, the depth of each surgical clip is measured directly from the orthogonal films or calculated from the rotational stereo shift films. With this information, the physician can determine the appropriate electron energy to cover the target volume. This method was tested by comparison with depths measured from CT scan, and close agreement was demonstrated.