Guo Peiyuan, Wang Zhentian, Wu Chengpeng, Zhu Xiaohua, Zhang Li
Department of Engineering Physics, Tsinghua University, Beijing, China.
Key Laboratory of Particle & Radiation Imaging (Tsinghua University) of Ministry of Education, Beijing, China.
J Xray Sci Technol. 2022;30(5):891-901. doi: 10.3233/XST-221162.
X-ray grating interferometry normally requires multiple steps and exposures, causing a prolonged imaging time. There is motivation to use fewer steps to reduce scanning time and complexity, while keeping fidelity of the retrieved signals.
We propose an iterative signal retrieval method, extracting attenuation, dark field contrast (DFC), and differential phase contrast (DPC) signals from two X-ray exposures.
Two shots were captured at G2 grating positions with difference of 1/4 grating period. The algorithm consists of two stages. At the first stage, amplitude of sample phase stepping curve retrieved by virtual phase stepping (VPS) method, visibility and local phase of background phase stepping curve are used to limit the results to the proximity of the ground truth. After the second stage, three high-quality parameters, amplitude, visibility, and local phase, are retrieved through finetuning, and three signals are calculated. Simulated and real-sample experiments were conducted to validate this method.
We used standard phase stepping result as benchmark and calculated structural similarity (SSIM) and peak signal-to-noise ratio (PSNR) between benchmark and parameters retrieved by our dual-shot method and virtual phase stepping (VPS) method. For both simulated and real-sample experiments, the SSIM and PSNR value of dual-shot method are higher than those of VPS method. For real-sample method, we also conducted a three-step PS, and the SSIM and PSNR value of dual-shot method are slightly lower than those of three-step PS.
Using our dual-shot method demonstrates higher performance than other single-shot method in retrieving high-quality signals, and it also reduces radiation dose and time.
X射线光栅干涉测量通常需要多个步骤和多次曝光，导致成像时间延长。因此，人们希望在保持所获取信号保真度的同时，减少步骤以缩短扫描时间并降低复杂性。
我们提出一种迭代信号检索方法，从两次X射线曝光中提取衰减、暗场对比度（DFC）和微分相衬度（DPC）信号。
在G2光栅位置拍摄两张相差1/4光栅周期的照片。该算法包括两个阶段。在第一阶段，通过虚拟相移（VPS）方法检索的样品相移曲线的振幅、背景相移曲线的可见度和局部相位用于将结果限制在接近真实值的范围内。在第二阶段之后，通过微调检索三个高质量参数，即振幅、可见度和局部相位，并计算三个信号。进行了模拟和实际样品实验以验证该方法。
我们以标准相移结果为基准，计算了基准与通过我们的双曝光方法和虚拟相移（VPS）方法检索的参数之间的结构相似性（SSIM）和峰值信噪比（PSNR）。对于模拟和实际样品实验，双曝光方法的SSIM和PSNR值均高于VPS方法。对于实际样品方法，我们还进行了三步相移（PS），双曝光方法的SSIM和PSNR值略低于三步相移（PS）。
使用我们的双曝光方法在检索高质量信号方面比其他单曝光方法具有更高的性能，并且还减少了辐射剂量和时间。
