标题： 体组织质量密度、电子密度和元素组成的相互关系在放射治疗计划蒙特卡罗模拟中的应用 显示英文标题

标题： Relationship between mass density, electron density, and elemental composition of body tissues for Monte Carlo simulation in radiation treatment planning

摘要： 目的：对于放射治疗的蒙特卡罗模拟，每个系统的X射线CT数值都需要校准并转换为质量密度和元素组成。本研究旨在制定身体组织的材料特性，以实现从CT数值的实际两步转换。 方法：我们使用了构成参考成年男性和女性的身体组织的最新汇编。我们将质量、电子和元素密度之间的关系制定为折线，以连接代表性组织，在有限密度区域中对组织取质量加权平均值。我们比较了质量密度的折线函数与从先前研究中得出的电子密度的双线和元素密度的断线。 结果：在占身体质量1%的轻质骨小梁组织中，质量密度与其他密度之间通常具有高相关性，但不包括C、N和O。折线拟合到主要组织，并且通常与双线和断线一致。 结论：我们制定了身体组织的质量与电子密度之间的不变关系，以及从质量到元素密度的关系。该公式使得在治疗计划实践中进行蒙特卡罗模拟无需额外的CT数值校准负担。 显示英文摘要

摘要： Purpose: For Monte Carlo simulation of radiotherapy, x-ray CT number of every system needs to be calibrated and converted to mass density and elemental composition. This study aims to formulate material properties of body tissues for practical two-step conversion from CT number. Methods: We used the latest compilation on body tissues that constitute reference adult male and female. We formulated the relations among mass, electron, and elemental densities into polylines to connect representative tissues, for which we took mass-weighted mean for the tissues in limited density regions. We compared the polyline functions of mass density with a bi-line for electron density and broken lines for elemental densities, which were derived from preceding studies. Results: There was generally high correlation between mass density and the other densities except of C, N, and O for light spongiosa tissues occupying 1% of body mass. The polylines fitted to the dominant tissues and were generally consistent with the bi-line and the broken lines. Conclusions: We have formulated the invariant relations between mass and electron densities and from mass to elemental densities for body tissues. The formulation enables Monte Carlo simulation in treatment planning practice without additional burden with CT-number calibration.