%0 Journal Article
%T Scan Quality and Entrance Skin Dose in Thoracic CT: A Comparison between Bismuth Breast Shield and Posteriorly Centered Partial CT Scans
%A Rafel Tappouni
%A Bradley Mathers
%J ISRN Radiology
%D 2013
%R 10.5402/2013/457396
%X Objectives. To compare the effectiveness of the bismuth breast shield and partial CT scan in reducing entrance skin dose and to evaluate the effect of the breast shield on image quality (IQ). Methods. Nanodots were placed on an adult anthropomorphic phantom. Standard chest CT, CT with shield, and partial CT were performed. Nanodot readings and effective doses were recorded. 50 patients with chest CTs obtained both with and without breast shields were reviewed. IQ was evaluated by two radiologists and by measuring Hounsfield units (HUs) and standard deviation (SD) of HU in anterior subcutaneous region. Results. Breast shield and the partial CT scans reduced radiation to the anterior chest by 38% and 16%, respectively. Partial CT increased dose to the posterior chest by 37% and effective dose by 8%. Change in IQ in shield CT was observed in the anterior chest wall. Significant change in IQ was observed in 5/50 cases. The shield caused an increase of 20£¿HU ( ) and a 1.86 reduction in SD of HU ( ) in the anterior compared to posterior subcutaneous regions. Summary. Bismuth breast shield is more effective than the partial CT in reducing entrance skin dose while maintaining image quality. 1. Introduction Computed tomography (CT) has emerged as an important diagnostic tool in clinical medicine. Its use has grown exponentially over the years, rising from 3 million in 1980 to 67 million in 2006, an equivalent of a 600% increase from 1980 to 2006 [1]. This significant rise in frequency also brings into question the level of radiation exposure to patients. The potential carcinogenic effect of this increased radiation dose on radiosensitive tissues has fostered much concern recently [2] and breast tissue exposure from chest CT is an area of particular concern in females. In 2008, the International Commission of Radiation Protection (ICRP) increased the tissue weighting factor for the breast from 0.05 to 0.12 [3]. The radiation exposure to the breast from a chest CT is estimated to be 2.0¨C3.5 rad, which is equivalent to 10 mammograms or 100 chest radiographs [4]. These doses far exceed the American College of Radiology recommendation of 0.3£¿rad or less for a standard 2-view mammography. The delivery of 1£¿rad to a woman younger than age 35 years old is estimated to increase her lifetime risk of breast cancer by 13.6% [4¨C7]. Due to this risk, several techniques have been developed to reduce the radiation exposure to the breast during a chest CT. The in-plane bismuth breast shield has been shown to be effective at reducing radiation dose to the breast. An early study
%U http://www.hindawi.com/journals/isrn.radiology/2013/457396/