Optimisation of image reconstruction for phase-contrast x-ray Talbot–Lau imaging with regard to mechanical robustness
Optimisation of image reconstruction for phase-contrast x-ray Talbot–Lau imaging with regard to mechanical robustness
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DOI：
10.1088/0031-9155/61/17/6441
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发表时间：
2016-08
影响因子：
3.5
通讯作者：
M. Seifert;S. Kaeppler;C. Hauke;F. Horn;G. Pelzer;J. Rieger;T. Michel;C. Riess;G. Anton
中科院分区：
文献类型：
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作者：
M. Seifert;S. Kaeppler;C. Hauke;F. Horn;G. Pelzer;J. Rieger;T. Michel;C. Riess;G. Anton
基于X射线光栅的相衬成像，阿利亚其他外，在医学成像和非破坏性测试方面开辟了新的机会。因为，关于衰减特性和关于物体的折射特性的信息同时获得。Talbot-Lau成像需要参考或自由场图像的知识。Talbot-Lau干涉仪的长期稳定性与被测参考图像的有效性的时间跨度有关。期望将参考图像的有效性保持一天或更长时间以提高Talbot-Lau成像的可行性。然而，例如热和其他长期外部影响导致相位图像的漂移效应。因此，相位随时间推移而偏移，并且参考图像对于长期测量无效。因此，在微分相位对比图像中出现伪影。我们开发了一种算法来确定微分相衬图像的帮助下，只有一个校准图像，这是有效的一个长的时间周期。在这种称为相平面拟合法的算法的帮助下，可以节省测量时间，因为每次测量都不需要拍摄参考图像。另外，将干涉仪技术从实验室设置转移到常规成像系统，难以实现系统的必要刚性。因此，系统的振动或失真等短期效应会导致相位步进过程中的缺陷。因此，在Talbot-Lau成像的所有三种图像模态（微分相位衬度图像、衰减图像和暗场图像）中都会出现伪影。这对于相位对比成像的预期用途（例如，在临床常规或非破坏性测试中）是一个问题。在该出版物中，应用并补充Vargas等人的算法，以在主成分分析（PCA）的帮助下校正不准确的相位步长位置。因此，可以计算无伪影图像。随后，整个算法被称为PCA最小化算法。
X-ray grating-based phase-contrast imaging opens new opportunities, inter alia, in medical imaging and non-destructive testing. Because, information about the attenuation properties and about the refractive properties of an object are gained simultaneously. Talbot–Lau imaging requires the knowledge of a reference or free-field image. The long-term stability of a Talbot–Lau interferometer is related to the time span of the validity of a measured reference image. It would be desirable to keep the validity of the reference image for a day or longer to improve feasibility of Talbot–Lau imaging. However, for example thermal and other long-term external influences result in drifting effects of the phase images. Therefore, phases are shifting over time and the reference image is not valid for long-term measurements. Thus, artifacts occur in differential phase-contrast images. We developed an algorithm to determine the differential phase-contrast image with the help of just one calibration image, which is valid for a long time-period. With the help of this algorithm, called phase-plane-fit method, it is possible to save measurement-time, as it is not necessary to take a reference image for each measurement. Additionally, transferring the interferometer technique from laboratory setups to conventional imaging systems the necessary rigidity of the system is difficult to achieve. Therefore, short-term effects like vibrations or distortions of the system lead to imperfections within the phase-stepping procedure. Consequently, artifacts occur in all three image modalities (differential phase-contrast image, attenuation image and dark-field image) of Talbot–Lau imaging. This is a problem with regard to the intended use of phase-contrast imaging for example in clinical routine or non-destructive testing. In this publication an algorithm of Vargas et al is applied and complemented to correct inaccurate phase-step positions with the help of a principal component analysis (PCA). Thus, it is possible to calculate the artifact free images. Subsequently, the whole algorithm is called PCA minimization algorithm.