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首页> 美国卫生研究院文献>Sensors (Basel Switzerland) >Calculation of Stopping-Power Ratio from Multiple CT Numbers Using Photon-Counting CT System: Two- and Three-Parameter-Fitting Method
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Calculation of Stopping-Power Ratio from Multiple CT Numbers Using Photon-Counting CT System: Two- and Three-Parameter-Fitting Method

机译：使用光子计数CT系统计算多CT号的停止功率比：双和三参数拟合方法

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The two-parameter-fitting method (PFM) is commonly used to calculate the stopping-power ratio (SPR). This study proposes a new formalism: a three-PFM, which can be used in multiple spectral computed tomography (CT). Using a photon-counting CT system, seven rod-shaped samples of aluminium, graphite, and poly(methyl methacrylate) (PMMA), and four types of biological phantom materials were placed in a water-filled sample holder. The X-ray tube voltage and current were set at 150 kV and 40 μA respectively, and four CT images were obtained at four threshold settings. A semi-empirical correction method that corrects the difference between the CT values from the photon-counting CT images and theoretical values in each spectral region was also introduced. Both the two- and three-PFMs were used to calculate the effective atomic number and electron density from multiple CT numbers. The mean excitation energy was calculated via parameterisation with the effective atomic number, and the SPR was then calculated from the calculated electron density and mean excitation energy. Then, the SPRs from both methods were compared with the theoretical values. To estimate the noise level of the CT numbers obtained from the photon-counting CT, CT numbers, including noise, were simulated to evaluate the robustness of the aforementioned PFMs. For the aluminium and graphite, the maximum relative errors for the SPRs calculated using the two-PFM and three-PFM were 17.1% and 7.1%, respectively. For the PMMA and biological phantom materials, the maximum relative errors for the SPRs calculated using the two-PFM and three-PFM were 5.5% and 2.0%, respectively. It was concluded that the three-PFM, compared with the two-PFM, can yield SPRs that are closer to the theoretical values and is less affected by noise.
机译：两参数拟合方法（PFM）通常用于计算停止功率比（SPR）。本研究提出了一种新的形式主义：三PFM，可用于多谱计算断层扫描（CT）。使用光子计数CT系统，将七种铝，石墨和聚（甲基丙烯酸甲酯）（PMMA）的杆状样品（PMMA）和四种类型的生物模体材料置于充水的样品架中。 X射线管电压和电流分别设定为150kV和40μA，在四个阈值设置下获得四个CT图像。还引入了校正来自光子计数CT图像中CT值与每个光谱区域中的理论值之间的差异的半经验校正方法。两种和三PFMS都用于从多个CT号计算有效原子数和电子密度。通过具有有效原子序数的参数化计算平均激发能量，然后从计算的电子密度和平均激发能量计算SPR。然后，将来自两种方法的SPS与理论值进行比较。为了估计从光子计数CT获得的CT号的噪声水平，模拟包括噪声的CT号，以评估上述PFM的鲁棒性。对于铝和石墨，使用双PFM和三-PFM计算的SPR的最大相对误差分别为17.1％和7.1％。对于PMMA和生物模体材料，使用双PFM和三-PFM计算的SPR的最大相对误差分别为5.5％和2.0％。结论是，与双PFM相比，三PFM可以产生更接近理论值并且受到噪声影响的SPR。

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