Background

In diagnostic X-ray computed tomography (CT) imaging, some applications, such as dose measurement using the Monte Carlo method and material decomposition using dual/multi-energy approaches, rely on accurate knowledge of the energy spectrum of the X-ray beam. In this regard, X-ray detectors providing an accurate estimation of the X-ray spectrum could greatly impact the quality of dual/multi-energy CT imaging and patient-specific dosimetry.

Purpose

The aim of this study is to estimate the intrinsic efficiency and energy resolution of different types of solid-state gamma-ray detectors in order to generate a precise dual-energy X-ray beam from the conventional x-ray tube using external X-ray filters.

Materials and methods

The X-ray spectrum of a clinical X-ray tube was experimentally measured using a high purity Germanium detector (HPGe) and the obtained spectrum validated by Monte Carlo (MC) simulations. The obtained X-ray spectrum from the experiment was employed to assess the energy resolution and detection efficiency of different inorganic scintillators and semiconductor-based solid-state detectors, namely HPGe, BGO, NaI, and LYSO, using MC simulations. The best performing detector was employed to experimentally create and measure a dual-energy X-ray spectrum through applying attenuating filters to the original X-ray beam.

Results

The simulation results indicated 9.16% energy resolution for the HPGe detector wherein the full width-at-half-maximum (FWHM) of the energy resolution for the HPGe detector was about 1/3rd of the other inorganic detectors. The X-ray spectra estimated from the various source energies exhibited a good agreement between experimental and simulation results with a maximum difference of 6%. Owing to the high-energy discrimination power of the HPGe detector, a dual-energy X-ray spectrum was created and measured from the original X-ray spectrum using 0.5 and 4.5 mm Aluminum external filters, which involves 70 and 140 keV energy peaks with 8% overlap.

Conclusion

The experimental measurements and MC simulations of the HPGe detector exhibited close agreement in high-energy resolution estimation of the X-ray spectrum. Given the accurate measurement of the X-ray spectrum with the HPGe detector, a dual-energy X-ray spectrum was generated with minimal energy overlap using external X-ray filters.

中文翻译：

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在临床前微型 CT 扫描仪中使用 BGO、NaI、LYSO 和 HPGe 探测器进行 X 射线管光谱测量的比较：蒙特卡罗模拟和实际实验

背景

在诊断性 X 射线计算机断层扫描 (CT) 成像中，某些应用（例如使用蒙特卡罗方法的剂量测量和使用双/多能量方法的材料分解）依赖于对 X 射线束能谱的准确了解。在这方面，提供对 X 射线光谱的准确估计的 X 射线探测器可能会极大地影响双/多能 CT 成像和患者特定剂量测定的质量。

目的

本研究的目的是估计不同类型固态伽马射线探测器的固有效率和能量分辨率，以便使用外部 X 射线从传统 X 射线管中产生精确的双能 X 射线束。过滤器。

材料和方法

临床 X 射线管的 X 射线光谱使用高纯度锗探测器 (HPGe) 进行实验测量，获得的光谱通过蒙特卡罗 (MC) 模拟验证。从实验中获得的 X 射线光谱用于使用 MC 模拟评估不同无机闪烁体和基于半导体的固态探测器（即 HPGe、BGO、NaI 和 LYSO）的能量分辨率和探测效率。通过对原始 X 射线束应用衰减滤波器，采用性能最佳的探测器以实验方式创建和测量双能 X 射线光谱。

结果

模拟结果表明 HPGe 探测器的能量分辨率为 9.16%，其中 HPGe 探测器的能量分辨率的半高全宽 (FWHM) 约为其他无机探测器的 1/3。从各种源能量估计的 X 射线光谱在实验和模拟结果之间表现出良好的一致性，最大差异为 6%。由于 HPGe 探测器的高能量分辨能力，使用 0.5 和 4.5 毫米铝外部滤波器从原始 X 射线光谱创建和测量双能 X 射线光谱，其中涉及 70 和 140 keV 能量峰值， 8% 重叠。

结论

HPGe 探测器的实验测量和 MC 模拟在 X 射线光谱的高能量分辨率估计方面表现出非常一致的结果。鉴于使用 HPGe 探测器对 X 射线光谱的准确测量，使用外部 X 射线滤波器生成了具有最小能量重叠的双能 X 射线光谱。