Radiation Dose to the Breast by 64-slice CT: Effects of Scanner Model and Study Protocol.
This work aimed to study the effects of scanner model and study protocol on radiation dose received by breast tissues from 64-slice computed tomography (CT) studies.



Four scanner models and three study protocols were used in scanning an anthropomorphic phantom with breast modules. Each protocol follows recommendations or guidelines from the American Association of Physicists in Medicine and the American College of Radiology. Twenty thermoluminescent dosimeters were placed inside the breast modules to measure breast tissue doses. Both the absolute and the normalized breast tissue doses were analyzed.



The mean glandular doses of a lung cancer screening CT, a chest/abdomen/pelvis CT, and a virtual colonoscopy CT are equivalent to less than 1, 5-7, and 1-3 two-view digital mammograms, respectively, for a standard-sized patient. The normalized breast dose differs significantly (P < 0.01) between lung cancer screening CT and chest/abdomen/pelvis CT; however, it shows less than ±10% variation among scanner models for the same protocol. In virtual colonoscopy CT, breast tissue dose decreases with the distance between local tissues to the edge of the x-ray field, although the decreasing trend varies for different scanner models and protocol settings.



When breasts are entirely included in the primary x-ray field, breast dose by 64-slice CT is mainly protocol dependent, with the normalized breast dose about 15% lower for protocols with modulated mA than for those with constant mA; when breasts are only partially included in the primary beam field, breast dose by 64-slice CT is dependent on both the scanner model and the protocol settings.
Department of Radiology, University of Cincinnati, 234 Goodman Street PO Box 670761 Cincinnati, OH 45267-0761. Electronic address: qizhihua99@gmail.com.
Zhihua
Z
Qi
Department of Radiology, University of Cincinnati, 234 Goodman Street PO Box 670761 Cincinnati, OH 45267-0761.
Lisa C
LC
Lemen
Department of Radiology, University of Cincinnati, 234 Goodman Street PO Box 670761 Cincinnati, OH 45267-0761.
Michael
M
Lamba
Department of Radiology, University of Cincinnati, 234 Goodman Street PO Box 670761 Cincinnati, OH 45267-0761.
Hua-Hsuan
HH
Chen
Department of Radiology, University of Cincinnati, 234 Goodman Street PO Box 670761 Cincinnati, OH 45267-0761.
Ranasinghage
R
Samaratunga
Department of Radiology, University of Cincinnati, 234 Goodman Street PO Box 670761 Cincinnati, OH 45267-0761.
Mary
M
Mahoney
Department of Radiology, University of Colorado - Denver, School of Medicine, Aurora, CO 80045.
R Edward
RE
Hendrick
D001940:Breast / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D012107:Research Design; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods*
Computed tomography; breast dose; radiation dosimetry