Monte Carlo assessment of computed tomography dose to tissue adjacent to the scanned volume.
Monte Carlo assessment of computed tomography dose to tissue adjacent to the scanned volume.
复制标题
蒙特卡罗评估扫描体积附近组织的计算机断层扫描剂量。
DOI：
10.1118/1.1312809
复制
发表时间：
2000
期刊：
影响因子：
3.8
通讯作者：
Seibert,JA
中科院分区：
文献类型：
--
作者：
Boone,JM;Cooper3rd,VN;Nemzek,WR;McGahan,JP;Seibert,JA
有时需要对内部器官或胚胎或胎儿的辐射剂量进行评估，以进行风险评估或比较影像学研究。有限的资源阻碍了准确评估在计算机断层扫描（CT）中实际扫描的组织体积之外的位置所接受的辐射剂量的能力。本研究的目的是评估外周剂量，并为剂量评估提供表格数据。使用经过验证的蒙特卡罗模拟技术计算了沿直径为16和32 cm的水等效圆柱形幻影长度的剂量分布。为了进一步验证，在物理测量和蒙特卡罗导出的空气kerma剖面之间进行了比较，并显示出极好的一致性（1%至2%）。用波束整形滤波器研究了80,100,120和140kvp的多能x射线能谱。利用垂直于圆柱体长轴的模拟光子输入，确定了圆柱体中三个深度（中心、中深度和表面）剂量分布的线扩散函数（LSF）。然后用适当的数学方法计算LSF数据沿圆柱体长轴的剂量分布。螺旋扫描和轴向扫描得到的剂量分布近似相等。在距离CT扫描组织体积边缘约3cm处，辐射剂量呈指数衰减。在100毫安秒（mAs）标准下，生成了一系列表格，可以直接评估CT扫描体积内和周围的剂量。这些表格对医学物理学家和放射科医生在估计CT扫描体积边缘以外的部位的剂量时应该是有用的。
The assessment of the radiation dose to internal organs or to an embryo or fetus is required on occasion for risk assessment or for comparing imaging studies. Limited resources hinder the ability to accurately assess the radiation dose received to locations outside the tissue volume actually scanned during computed tomography (CT). The purpose of this study was to assess peripheral doses and provide tabular data for dose evaluation. Validated Monte Carlo simulation techniques were used to compute the dose distribution along the length of water‐equivalent cylindrical phantoms, 16 and 32 cm in diameter. For further validation, comparisons between physically measured and Monte Carlo‐derived air kerma profiles were performed and showed excellent (1% to 2%) agreement. Polyenergetic x‐ray spectra at 80, 100, 120, and 140 kVp with beam shaping filters were studied. Using simulated photons input to the cylinders perpendicular to their long axis, line spread functions (LSF) of the dose distribution were determined at three depths in the cylinders (center, mid‐depth, and surface). The LSF data were then used with appropriate mathematics to compute dose distributions along the long axis of the cylinder. The dose distributions resulting from helical scans and axial scans were approximately equivalent. Beyond about 3 cm from the edge of the CT scanned tissue volume, the fall‐off of radiation dose was exponential. A series of tables normalized at 100 milliampere seconds (mAs) were produced which allow the straightforward assessment of dose within and peripheral to the CT scanned volume. The tables should be useful for medical physicists and radiologists in the estimation of dose to sites beyond the edge of the CT scanned volume.