Lab-based X-ray computed tomography (XCT) systems use X-ray sources that emit a polychromatic X-ray spectrum and detectors that do not detect all X-ray photons with the same efficiency. A consequence of using a polychromatic X-ray source is that beam hardening artefacts may be present in the reconstructed data, and the presence of such artefacts can degrade XCT image quality and affect quantitative analysis. If the product of the X-ray spectrum and the quantum detection efficiency (QDE) of the detector are known, alongside the material of the scanned object, then beam hardening artefacts can be corrected algorithmically. In this work, a method for estimating the product of the X-ray spectrum and the detector’s QDE is offered. The method approximates the product of the X-ray spectrum and the QDE as a Bézier curve, which requires only eight fitting parameters to be estimated. It is shown experimentally and through simulation that Bézier curves can be used to accurately simulate polychromatic attenuation and hence be used to correct beam hardening artefacts. The proposed method is tested using measured attenuation data and then used to calculate a beam hardening correction for an aluminium workpiece; the beam hardening correction leads to an increase in the contrast-to-noise ratio of the XCT data by 41% and the removal of cupping artefacts. Deriving beam hardening corrections in this manner is more versatile than using conventional material-specific step wedges.

中文翻译：

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CT系统X射线能谱与量子探测效率乘积的估计及其在射束硬化校正中的应用

基于实验室的 X 射线计算机断层扫描 (XCT) 系统使用发射多色 X 射线光谱的 X 射线源和不能以相同效率检测所有 X 射线光子的探测器。使用多色 X 射线源的结果是，重建数据中可能存在光束硬化伪影，并且此类伪影的存在会降低 XCT 图像质量并影响定量分析。如果 X 射线光谱和探测器的量子探测效率 (QDE) 的乘积以及被扫描物体的材料已知，则可以通过算法校正光束硬化伪影。在这项工作中，提供了一种估计 X 射线光谱和探测器 QDE 乘积的方法。该方法将X射线能谱和QDE的乘积近似为贝塞尔曲线，只需要估计8个拟合参数。实验和仿真表明，贝塞尔曲线可用于精确模拟多色衰减，从而可用于校正光束硬化伪影。使用测量的衰减数据对所提出的方法进行测试，然后用于计算铝工件的束硬化校正；束硬化校正使 XCT 数据的对比度噪声比提高了 41%，并消除了杯突伪影。以这种方式导出光束硬化校正比使用传统的特定材料阶梯楔块更通用。