Kilovoltage cone-beam CT imaging dose during breast radiotherapy: A dose comparison between a left and right breast setup
The purpose of this study was to investigate the delivered dose from a kilovoltage cone-beam computed tomography (kV-CBCT) acquired in breast treatment position for a left and right breast setup. The dose was measured with thermoluminescent dosimeters positioned within a female anthropomorphic phantom at organ locations. Imaging was performed on an Elekta Synergy XVI system with the phantom setup on a breast board. The image protocol involved 120. kVp, 140. mAs, and a 270 degrees arc rotation clockwise 0 degrees to 270 degrees for the left breast setup and 270 degrees to 180 degrees for the right breast setup (maximum arc rotations possible). The dose delivered to the left breast, right breast, and heart was 5.1. mGy, 3.9. mGy, and 4.0. mGy for the left breast setup kV-CBCT, and 6.4. mGy, 6.0. mGy, and 4.8. mGy for the right breast setup kV-CBCT, respectively. The rotation arc of the kV-CBCT influenced the dose delivered, with the right breast setup kV-CBCT found to deliver a dose of up to 4. mGy or 105 percent higher to the treated breast's surface in comparison with the left breast setup. This is attributed to the kV-CBCT source being more proximal to the anterior of the phantom for a right breast setup, whereas the source is more proximal to the posterior of the patient for a left-side scan. 2014 American Association of Medical Dosimetrists.