Simulation of photon-counting detectors for conversion of dual-energy-subtracted computed tomography number to electron density
Simulation of photon-counting detectors for conversion of dual-energy-subtracted computed tomography number to electron density
复制标题
用于将双能减法计算机断层扫描数转换为电子密度的光子计数探测器的模拟
DOI：
10.1007/s12194-018-00497-0
复制
发表时间：
2019
影响因子：
1.6
通讯作者：
Saito Masatoshi
中科院分区：
文献类型：
--
作者：
渡辺信博;堀田晴美;Saito Masatoshi
为了在放射治疗计划中准确校正组织不均匀性，作者先前提出了能量减影计算机断层扫描（CT）数到电子密度的转换（ΔHU-ρ转换）。本研究的目的是通过对具有两个能量箱的光子计数探测器（PCD）系统进行双能量CT图像模拟，提供一种研究用于ΔHU-ρ转换的光子计数探测器（PCD）的准确性的方法。为了优化管电压和阈值能量，使用三种类型的虚拟体模评估了图像噪声和ρ校准误差：直径35厘米的纯水体模、配备16个插件的直径33厘米的固体水替代体模，以及另一个固体水替代体模直径为25厘米。第三个体模用于研究对象尺寸对PCD的ρ e校准精度的影响。考虑了PCD能量响应的两种不同情景，对应于理想和现实情况。此外，提出了一种简单的校正方法，用于改善实际PCD中双能量的光谱分离，以补偿其性能损失。在实际的PCD情况下，存在图像噪声和ρ e校准误差之间的折衷。此外，最弱的图像噪声几乎是理想情况下的两倍，并且ρ e校准误差对于任何阈值能量都没有达到实际水平。尽管如此，所提出的校正方法可能会将实际PCD的ρ e校准误差降低到理想情况的水平，从而产生更准确的ρ值，受物体尺寸变化的影响较小。
For accurate tissue-inhomogeneity correction in radiotherapy treatment planning, the author previously proposed a conversion of the energy-subtracted computed tomography (CT) number to electron density (ΔHU–ρeconversion). The purpose of the present study was to provide a method for investigating the accuracy of a photon-counting detector (PCD) used in the ΔHU–ρeconversion by performing dual-energy CT image simulations of a PCD system with two energy bins. To optimize the tube voltage and threshold energy, the image noise and errors inρecalibration were evaluated using three types of virtual phantoms: a 35-cm-diameter pure water phantom, 33-cm-diameter solid water surrogate phantom equipped with 16 inserts, and another solid water surrogate phantom with a 25-cm diameter. The third phantom was used to investigate the effect of the object’s size on theρe-calibration accuracy of PCDs. Two different scenarios for the PCD energy response were considered, corresponding to the ideal and realistic cases. In addition, a simple correction method for improving the spectral separation of the dual energies in a realistic PCD was proposed to compensate for its performance loss. In the realistic PCD case, there exists a trade-off between the image noise andρe-calibration errors. Furthermore, the weakest image noise was nearly twice that for the ideal case, and theρe-calibration error did not reach practical levels for any threshold energy. Nevertheless, the proposed correction method is likely to decrease theρe-calibration errors of a realistic PCD to the level of the ideal case, yielding more accurateρevalues that are less affected by object size variation.