Department of Physics, University at Albany, Albany, New York, USA.
Nuclear Science and Technology, Beijing Normal University, Beijing, China.
Med Phys. 2021 Nov;48(11):6642-6657. doi: 10.1002/mp.15247. Epub 2021 Oct 11.
X-ray phase and dark-field (DF) imaging have been shown to improve the diagnostic capabilities of X-ray systems. However, these methods have found limited clinical use due to the need for multiple precision gratings with limited field of view or requirements on X-ray coherence that may not be easily translated to clinical practice. This work aims to develop a practicable X-ray phase and DF imaging system that could be translated and practiced in the clinic.
This work employs a conventional source to create structured illumination with a simple wire mesh. A mesh-shifting algorithm is used to allow wider Fourier windowing to enhance resolution. Deconvolution of the source spot width and camera resolution improves accuracy. Polycapillary optics are employed to enhance coherence. The effects of incorporating optics with two different focal lengths are compared. Information apparent in enhanced absorption images, phase images, and DF images of fat embedded phantoms were compared and subjected to a limited receiver operator characteristic (ROC) study. The DF images of the moist and dry porous object (sponges) were compared.
The mesh-based phase and DF imaging system constructs images with three different information types: scatter-free absorption images, differential phase images, and scatter magnitude/DF images, simultaneously from the same original image. The polycapillary optic enhances the coherence of the beam. The deblurring technique corrects the phase signal error due to geometrical blur and the limitation of the camera modulation transfer function (MTF) and removes image artifacts to improve the resolution in a single shot. The mesh-shifting method allows the use of a wider Fourier processing window, which gives even higher resolution, at the expense of an increased dose. The limited ROC study confirms the efficacy of the system over the conventional system. DF images of moist and dry porous object show the significance of the system in the imaging of lung infections.
The mesh-based X-ray phase and DF imaging system is an inexpensive and easy setup in terms of alignment and data acquisition and can produce phase and DF images in a single shot with wide field of view. The system shows significant potential for use in diagnostic imaging in a clinical setting.
X 射线相位和暗场（DF）成像是提高 X 射线系统诊断能力的有效方法。然而，由于需要具有有限视场的多个精密光栅或对 X 射线相干性的要求，这些方法在临床上的应用受到限制，这些要求可能不容易转化为临床实践。本工作旨在开发一种可行的 X 射线相位和 DF 成像系统，可以在临床上进行转化和应用。
本工作采用传统光源，利用简单的金属网栅产生结构照明。采用网格移动算法，允许更宽的傅里叶窗口化以提高分辨率。通过对源光斑宽度和相机分辨率进行反卷积，提高了准确性。采用聚光镜来增强相干性。比较了两种不同焦距的光学元件的效果。比较了嵌入脂肪的体模的增强吸收图像、相位图像和 DF 图像中的信息，并进行了有限的接收者操作特征（ROC）研究。比较了湿润和干燥多孔物体（海绵）的 DF 图像。
基于网格的相位和 DF 成像系统构建了三种不同信息类型的图像：无散射吸收图像、差分相位图像和散射幅度/DF 图像，这些图像都来自同一原始图像。聚光镜增强了光束的相干性。去模糊技术可以纠正由于几何模糊和相机调制传递函数（MTF）的限制而导致的相位信号误差，并消除图像伪影，从而在单次拍摄中提高分辨率。网格移动方法允许使用更宽的傅里叶处理窗口，这在牺牲剂量的情况下可以获得更高的分辨率。有限的 ROC 研究证实了该系统相对于传统系统的有效性。湿润和干燥多孔物体的 DF 图像显示了该系统在肺部感染成像中的重要性。
基于网格的 X 射线相位和 DF 成像系统在对准和数据采集方面具有成本效益，并且可以在单次拍摄中产生具有宽视场的相位和 DF 图像。该系统在临床诊断成像中具有很大的应用潜力。
