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首页> 外文期刊>Medical Physics >A comprehensive analysis of DgN(CT) coefficients for pendant-geometry cone-beam breast computed tomography.
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A comprehensive analysis of DgN(CT) coefficients for pendant-geometry cone-beam breast computed tomography.

机译：DgN（CT）系数的悬垂几何锥束乳房计算机断层扫描的综合分析。

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The use of a computed tomography (CT) scanner specifically designed for breast imaging has been proposed by several investigators. In this study, the radiation dose due to breast CT was evaluated using Monte Carlo techniques over a range of parameters pertinent to the cone-beam pendant geometry thought to be most appropriate. Monte Carlo dose computations were validated by comparison with physical measurements made on a prototype breast CT scanner under development in our laboratory. The Monte Carlo results were then used to study the influence of cone angle, the use of a beam flattening ("bow-tie") filter, glandular fraction, breast length and source-to-isocenter distance. These parameters were studied over a range of breast diameters from 10 to 18 cm, and for both monoenergetic (8-140 keV by 1 keV intervals) and polyenergetic x-ray beams (30-100 kVp by 5 kVp intervals. Half value layer at 80 kVp = 5.3 mm Al). A parameter referring to the normalized glandular dose in CT (DgN(CT)) was defined which is the ratio of the glandular dose in the breast to the air kerma at isocenter. There was no significant difference (p = 0.743) between physically measured and Monte Carlo derived results. Fan angle, source-to-isocenter distance, and breast length have relatively small influences on the radiation dose in breast CT. Glandular fraction (0% versus 100%) for 10 cm breasts at 80 kVp had approximately a 10% effect on DgN(CT), and a 20% effect was observed for an 18 cm breast diameter. The use of a bow-tie filter had the potential to reduce breast dose by approximately 40%. X-ray beam energy and breast diameter had significant influence on the DgN(CT) parameters, with higher DgN(CT) values for higher energy beams and smaller breast diameters. DgN(CT) values (mGy/mGy) at 80 kVp ranged from 0.95 for an 8 cm diam 50% glandular breast to 0.78 for an 18 cm 50% glandular breast. The results of this investigation should be useful for those interested computing the glandular breast dose for geometries relevant to dedicated breast CT.
机译：几位研究者已经提出使用专门为乳房成像设计的计算机断层扫描（CT）扫描仪。在这项研究中，使用蒙特卡洛技术在与认为最合适的锥束悬挂器几何形状有关的一系列参数上评估了由于胸部CT引起的辐射剂量。蒙特卡洛剂量计算是通过与在我们实验室中开发的原型乳房CT扫描仪上进行的物理测量结果进行比较来验证的。然后将蒙特卡洛结果用于研究锥角的影响，使用光束展平（“领结”）滤镜，腺体比例，乳房长度以及源到等中心点的距离。这些参数是在10至18 cm的乳房直径范围内进行研究的，对于单能（8-140 keV，间隔为1 keV）和多能X射线束（30-100 kVp，间隔为5 kVp）进行了研究。 80 kVp = 5.3毫米铝）。定义了参考CT中标准化腺体剂量（DgN（CT））的参数，该参数是等中心点的乳房中腺体剂量与空气比释动能的比值。物理测量结果与蒙特卡洛得出的结果之间没有显着差异（p = 0.743）。扇形角度，源到等距距离和乳房长度对乳房CT辐射剂量的影响相对较小。对于80 kVp的10 cm乳房，腺体分数（0％对100％）对DgN（CT）的影响约为10％，对于18 cm的乳房直径，观察到的影响为20％。领结式过滤器的使用有可能将乳房剂量减少约40％。 X射线束能量和乳房直径对DgN（CT）参数有显着影响，对于较高能量束和较小的乳房直径，DgN（CT）值较高。 80 kVp时的DgN（CT）值（mGy / mGy）范围从直径为8 cm的50％腺体乳腺的0.95到直径为18 cm的50％腺体乳腺的0.78。这项研究的结果对于有兴趣计算与专用乳腺CT相关的几何形状的腺体乳房剂量的研究人员应该有用。

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