Monte Carlo and Phantom Study of the Radiation Dose to the Body from Dedicated CT of the Breast1

Department of Radiology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA.
Radiology (Impact Factor: 6.87). 05/2008; 247(1):98-105. DOI: 10.1148/radiol.2471071080
Source: PubMed


To prospectively determine the radiation dose absorbed by the organs and tissues of the body during a dedicated breast computed tomography (CT) study by using Monte Carlo methods and a phantom.
By using the Geant4 Monte Carlo tool kit, the Cristy anthropomorphic phantom and the geometry of a dedicated breast CT prototype were simulated. The simulation was used to track x-rays emitted from the source until their complete absorption or exit from the simulation limits. The interactions of the x-rays with the 65 different volumes representing organs, bones, and other tissues of the phantom that resulted in energy deposition were recorded. These data were used to compute the radiation dose to the organs and tissues during a complete dedicated breast CT scan relative to the average glandular dose to the imaged breast (relative organ dose [ROD]), by using the x-ray spectra proposed for dedicated breast CT imaging. The effectiveness of a lead shield for reducing the dose to the organs was investigated.
The maximum ROD among the organs was for the ipsilateral lung with a maximum ROD of 3.25%, followed by ROD for the heart and the thymus. Of the skeletal tissues, the sternum received the highest dose with a maximum ROD to the bone marrow of 2.24% and to the bone surface of 7.74%. The maximum ROD to the uterus, representative of that of an early-stage fetus, was 0.026%. These maxima occurred for the highest-energy x-ray spectrum (80 kVp) that was analyzed. A lead shield does not substantially protect the organs that receive the highest dose from dedicated breast CT.
Although the dose to the organs from dedicated breast CT is substantially higher than that from planar mammography, it is comparable to or considerably lower than that reached by other radiographic procedures and much lower than that of other CT examinations.

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    • "Using limited angle reconstruction techniques, tomosynthesis provides some 3D information of the breast, and has been shown to deliver an increase in detection performance when used with mammography (Park et al 2007, Gur et al 2009, Rafferty et al 2013). Other researchers have pursued the development of dedicated computed tomography of the breast (breast CT); these systems use an acquisition geometry where the patient lies prone on a table, with a single pendant breast placed through a hole in the table (Boone et al 2001, Lindfors et al 2008, Sechopoulos et al 2008, Chen et al 2009, Madhav et al 2009, Yang et al 2009, Prionas et al 2010, Sechopoulos et al 2010, Shen et al 2011). The imaging hardware rotates 360° around the breast, capturing the data in 10–17 s. "
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