Abstract
Recently, specific computed tomography (CT) scanners have been equipped with organ‐based tube current modulation (TCM) technology. It is possible that organ‐based TCM will replace the conventional dose‐reduction technique of reducing the effective milliampere‐second. The aim of this study was to determine if organ‐based TCM could reduce radiation exposure to the breasts without compromising the image uniformity and beam hardening effect in thoracic CT examinations. Breast and skin radiation doses and the absorbed radiation dose distribution within a single section were measured with an anthropomorphic phantom and radiophotoluminescent glass dosimeters using four approaches to thoracic CT (reference, organ‐based TCM, copper shielding, and the combination of the above two techniques, hereafter referred to as the combination technique). The CT value and noise level were measured using the same calibration phantom. Organ‐based TCM and copper shielding reduced radiation doses to the breast by 23.7% and 21.8%, respectively. However, the CT value increased, especially in the anterior region, using copper shielding. In contrast, the CT value and noise level barely increased using organ‐based TCM. The combination technique reduced the radiation dose to the breast by 38.2%, but greatly increased the absorbed radiation dose from the central to the posterior regions. Moreover, the CT value increased in the anterior region and the noise level increased by more than 10% in the entire region. Therefore, organ‐based TCM can reduce radiation doses to breasts with only small increases in noise levels, making it preferable for specific groups of patients, such as children and young women.PACS numbers: 87.53.Bn; 87.57.Q‐; 87.57.qp
Highlights
Computed tomography (CT) is a medical imaging technique that is very effective for detecting lung cancer at an early stage.[1,2] the increase in CT examination frequency and higher doses of radiation in CT examinations compared with other X-ray diagnostic procedures have raised concerns about radiation exposure to patients.[3]. According to the International Commission on Radiological Protection Publication 103, the tissue weighting factor for the breasts has been raised from 0.05 to 0.12,(4) implying that overexposure to the breasts should be avoided
These results indicated that the organ-based Tube current modulation (TCM) and copper shielding approaches reduced the radiation dose to the breasts almost and that the combination technique was the most effective
The three dose-reduction techniques to the breast reduced the frontal radiation dose to the skin; the organ-based TCM and combination techniques increased the lateral and dorsal radiation doses to the skin
Summary
Computed tomography (CT) is a medical imaging technique that is very effective for detecting lung cancer at an early stage.[1,2] the increase in CT examination frequency and higher doses of radiation in CT examinations compared with other X-ray diagnostic procedures have raised concerns about radiation exposure to patients.[3]. Tube current modulation (TCM) techniques adjust the tube current along the angular (xy-axis), longitudinal (z-axis), or both directions, to optimize radiation dose to patients.[9,10] Recently, specific CT scanners have been equipped with an organ-based TCM feature. The technique involves reduction of the X-ray tube output in real time when it is directly in front of breasts or other dose-sensitive organs, such as thyroid gland and eye lens. When it is used in combination with xy-axis and z-axis TCMs, the organ-based and z-axis TCMs function, while the xy-axis TCM does not function. We believe that the organ-based TCM technique may replace breast shielding as the preferred dose-reduction technique to breasts
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