A simple formulation for deriving effective atomic numbers via electron density calibration from dual-energy CT data in the human body
A simple formulation for deriving effective atomic numbers via electron density calibration from dual-energy CT data in the human body
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DOI：
10.1002/mp.12176
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发表时间：
2017-06-01
期刊：
影响因子：
3.8
通讯作者：
Sagara, Shota
中科院分区：
文献类型：
--
作者：
Saito, Masatoshi;Sagara, Shota
目的：本研究的主要目的是提出一个简单的公式（我们称之为DEEDZ），用于通过双能（DE）CT数据的电子密度（qe）校准来推导有效原子序数（Zeff）。我们使用可用的光子横截面数据库对具有已知元素组成和质量密度的多种材料进行了DEEDZ方法的数值分析。新的转换方法也适用于以前发表的实验DECT数据，以验证其实际可行性。方法：我们进行了数值分析的DEEDZ转换方法的组织替代品，具有相同的化学成分和质量密度的商业组织表征幻影，以确定必要的参数的QE和Zeff校准的DEEDZ转换。然后将这些参数应用于ICRU报告46的人体等效组织，作为qe和Zeff未知的目标对象。使用XCOM光子截面数据库计算这些材料的衰减系数。我们还将DEEDZ转换应用于文献中可用的实验DECT数据，该数据使用双源CT扫描仪在80 kV和140 kV/Sn下测量两种不同形状和尺寸的商业体模。模拟的Zeff与几乎所有ICRU-46人体组织的参考值在Zeff范围从5.83（胆结石-胆固醇）至16.11（骨矿物质-羟基磷灰石）。所有材料与参比Zeff的相对偏差均在0.3%以内，但一个离群值（即甲状腺）的偏差为3.1%。这种差异的原因是甲状腺含有少量的碘，一种原子序数较大的元素（Z = 53）。在实验的情况下，我们证实，具有较少的拟合参数的简单配方，使校准Zeff作为准确的现有calibration procedure.Conclusions：DEEDZ转换方法的基础上提出的简单配方，可以方便地建设的qe和Zeff图像从采集DECT数据。(C)2017年美国医学物理学家协会
Purpose: The main objective of this study is to propose a simple formulation (which we called DEEDZ) for deriving effective atomic numbers (Zeff) via electron density (qe) calibration from dualenergy (DE) CT data. We carried out numerical analysis of this DEEDZ method for a large variety of materials with known elemental compositions and mass densities using an available photon cross sections database. The new conversion approach was also applied to previously published experimental DECT data to validate its practical feasibility.Methods: We performed numerical analysis of the DEEDZ conversion method for tissue surrogates that have the same chemical compositions and mass densities as a commercial tissue-characterization phantom in order to determine the parameters necessary for the qe and Zeff calibrations in the DEEDZ conversion. These parameters were then applied to the human-body-equivalent tissues of ICRU Report 46 as objects of interest with unknown qe and Zeff. The attenuation coefficients of these materials were calculated using the XCOM photon cross sections database. We also applied the DEEDZ conversion to experimental DECT data available in the literature, which was measured for two commercial phantoms of different shapes and sizes using a dual-source CT scanner at 80 kV and 140 kV/Sn.Results: The simulated Zeff ' s were in excellent agreement with the reference values for almost all of the ICRU-46 human tissues over the Zeff range from 5.83 (gallstones-cholesterol) to 16.11 (bone mineral- hydroxyapatite). The relative deviations from the reference Zeff were within 0.3% for all materials, except for one outlier that presented a 3.1% deviation, namely, the thyroid. The reason for this discrepancy is that the thyroid contains a small amount of iodine, an element with a large atomic number (Z = 53). In the experimental case, we confirmed that the simple formulation with less fit parameters enable to calibrate Zeff as accurately as the existing calibration procedure.Conclusions: The DEEDZ conversion method based on the simple formulation proposed could facilitate the construction of qe and Zeff images from acquired DECT data. (C) 2017 American Association of Physicists in Medicine