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Noise variance analysis using a flat panel x-ray detector: A method for additive noise assessment with application to breast CT applications

机译：使用平板X射线探测器进行噪声方差分析：一种用于乳房CT应用的附加噪声评估方法

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>Purpose: A simplified linear model approach was proposed to accurately model the response of a flat panel detector used for breast CT (bCT).>Methods: Individual detector pixel mean and variance were measured from bCT projection images acquired both in air and with a polyethylene cylinder, with the detector operating in both fixed low gain and dynamic gain mode. Once the coefficients of the linear model are determined, the fractional additive noise can be used as a quantitative metric to evaluate the system’s efficiency in utilizing x-ray photons, including the performance of different gain modes of the detector.>Results: Fractional additive noise increases as the object thickness increases or as the radiation dose to the detector decreases. For bCT scan techniques on the UC Davis prototype scanner (80 kVp, 500 views total, 30 frames∕s), in the low gain mode, additive noise contributes 21% of the total pixel noise variance for a 10 cm object and 44% for a 17 cm object. With the dynamic gain mode, additive noise only represents approximately 2.6% of the total pixel noise variance for a 10 cm object and 7.3% for a 17 cm object.>Conclusions: The existence of the signal-independent additive noise is the primary cause for a quadratic relationship between bCT noise variance and the inverse of radiation dose at the detector. With the knowledge of the additive noise contribution to experimentally acquired images, system modifications can be made to reduce the impact of additive noise and improve the quantum noise efficiency of the bCT system.
机译：>目的：提出了一种简化的线性模型方法，可以准确地对用于乳腺CT（bCT）的平板探测器的响应进行建模。>方法：从在空气中和使用聚乙烯圆柱体采集的bCT投影图像中测量，检测器以固定的低增益和动态增益模式运行。一旦确定了线性模型的系数，就可以将分数加性噪声用作量化指标，以评估系统利用X射线光子的效率，包括检测器的不同增益模式的性能。>结果：< / strong>随着物体厚度的增加或检测器的辐射剂量减少，分数累加噪声也会增加。对于UC Davis原型扫描仪上的bCT扫描技术（80 kVp，总共500个视图，30帧/秒），在低增益模式下，加性噪声对10 cm物体的总像素噪声方差贡献为21％，对于10 cm物体的贡献为44％一个17厘米的物体。在动态增益模式下，加性噪声仅代表10厘米对象的总像素噪声方差的2.6％，而17厘米对象为7.3％。>结论：存在与信号无关的加性噪声是bCT噪声方差与检测器辐射剂量的倒数之间呈二次关系的主要原因。有了附加噪声对实验获得的图像的贡献的知识，就可以进行系统修改，以减少附加噪声的影响并提高bCT系统的量子噪声效率。

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