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首页> 外文期刊>Physics in medicine and biology. >Beam hardening artefacts in computed tomography with photon counting, charge integrating and energy weighting detectors: a simulation study.
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Beam hardening artefacts in computed tomography with photon counting, charge integrating and energy weighting detectors: a simulation study.

机译：具有光子计数，电荷积分和能量加权检测器的计算机断层摄影术中的束硬化伪像：模拟研究。

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摘要

Photon counting x-ray imaging provides efficient rejection of the electronics noise, no pulse height (Swank) noise, less noise due to optimal photon energy weighting and the possibility of energy resolved image acquisition. These advantages apply also to CT when projection data are acquired using a photon counting detector. However, photon counting detectors assign a weighting factor of 1 to all detected photons whereas the weighting factor of a charge integrating detector is proportional to the energy of the detected photon. Therefore, data collected by photon counting and charge integrating detectors represent the 'hardening' of the photon beam passed through the object differently. This affects the beam hardening artefacts in the reconstructed CT images. This work represents the first comparative evaluation of the effect of photon counting, charge integrating and energy weighting photon detectors on beam hardening artefacts in CT. Beam hardening artefacts in CT images were evaluated for 20 cm and 14cm diameter water cylinders with bone and low contrast inserts, at 120 kVp and 90 kVp x-ray tube voltages, respectively. It was shown that charge integrating results in 1.8% less beam hardening artefacts from bone inserts (i.e., CT numbers in the 'shadow' of the bone are less by 1.8% as compared to CT numbers over the periphery of the image), as compared to photon counting. However, optimal photon energy weighting, which provides highest SNR, results in 7.7% higher beam hardening artefacts from bone inserts as compared to photon counting. The magnitude of the 'cupping' artefacts was lower by 1% for charge integrating and higher by 6.1% for energy weighting acquisitions as compared to photon counting. Only the photon counting systems provide an accurate representation of the beam hardening effect due to its flat energy weighting. Because of their energy dependent weighting factors, the charge integrating and energy weighting systems do not provide accurate representation of the beam hardening effect.
机译：光子计数X射线成像可有效抑制电子噪声，无脉冲高度（Swank）噪声，归因于最佳光子能量加权的噪声较小以及能量分辨图像采集的可能性。当使用光子计数检测器获取投影数据时，这些优势也适用于CT。但是，光子计数检测器为所有检测到的光子分配加权因子1，而电荷积分检测器的加权因子与检测到的光子的能量成比例。因此，由光子计数和电荷积分检测器收集的数据以不同方式表示通过物体的光子束的“硬化”。这会影响重建的CT图像中的光束硬化伪像。这项工作代表了对光子计数，电荷积分和能量加权光子探测器对CT中的束硬化伪像的影响的第一个比较评估。在分别具有120 kVp和90 kVp X射线管电压的情况下，对带有骨骼和低对比度插入物的20 cm和14cm直径水缸的CT图像中的束硬化伪像进行了评估。结果表明，电荷积分使来自骨插入物的束硬化伪影减少了1.8％（即，与图像外围的CT数相比，骨骼“阴影”中的CT数减少了1.8％）。光子计数。但是，与光子计数相比，提供最高SNR的最佳光子能量加权会导致来自骨骼插入物的光束硬化伪像增加7.7％。与光子计数相比，“积分”伪像的量级对于电荷积分而言降低了1％，对于能量加权采集而言，降低了6.1％。由于其平坦的能量加权，仅光子计数系统可提供光束硬化效果的准确表示。由于它们依赖于能量的加权因子，电荷积分和能量加权系统不能提供束硬化效应的准确表示。

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