A comprehensive analysis of DgNCT coefficients for pendant-geometry cone-beam breast computed tomography
A comprehensive analysis of DgNCT coefficients for pendant-geometry cone-beam breast computed tomography
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DOI：
10.1118/1.1636571
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发表时间：
2004-02-01
期刊：
影响因子：
3.8
通讯作者：
Nelson, TR
中科院分区：
文献类型：
--
作者：
Boone, JM;Shah, N;Nelson, TR
一些研究者已经提出使用专门设计用于乳腺成像的计算机断层扫描（CT）扫描仪。在本研究中，使用Monte Carlo技术在与被认为最合适的锥束悬垂几何结构相关的一系列参数范围内评价了乳腺CT的辐射剂量。蒙特卡罗剂量计算进行了验证，通过比较与物理测量的原型乳房CT扫描仪在我们的实验室正在开发中。然后使用Monte Carlo结果来研究锥角的影响，使用束平坦（“蝴蝶结”）过滤器，腺体分数，乳房长度和源到等中心点距离。在10至18 cm的乳房直径范围内，对单能（8-140 keV × 1 keV间隔）和多能X射线束（30-100 kVp × 5 kVp间隔）的这些参数进行了研究。80 kVp下的半值层= 5.3 mm Al）。定义了一个涉及CT中标准化腺体剂量（DgN（CT））的参数，该参数是乳房中腺体剂量与等中心处空气比释动能的比率。物理测量结果与Monte Carlo推导结果之间无显著差异（p = 0.743）。扇形角、源到等中心距离和乳房长度对乳房CT中的辐射剂量的影响相对较小。在80 kVp下，10 cm乳房的腺体分数（0%与100%）对DgN（CT）的影响约为10%，对18 cm乳房直径的影响为20%。使用蝴蝶结过滤器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）参数有显著影响，较高能量束和较小乳房直径的DgN（CT）值较高。80 kVp时的DgN（CT）值（mGy/mGy）范围为0.95（直径为8 cm，50%腺体乳腺）至0.78（直径为18 cm，50%腺体乳腺）。这项调查的结果应该是有用的，对于那些有兴趣计算乳腺腺体剂量的几何形状相关的专用乳腺CT。(C)2004年美国医学物理学家协会。
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. (C) 2004 American Association of Physicists in Medicine.