X 射線相位對(duì)比成像提供了一種區(qū)分具有相似密度和有效原子序數(shù)的材料的方法,使用傳統(tǒng)的 X 射線吸收對(duì)比很難做到這一點(diǎn)。近年來,已經(jīng)開發(fā)了多種方法來使用非相干實(shí)驗(yàn)室源獲取 X 射線相位對(duì)比圖像。單掩模邊緣照明設(shè)置已被證明能應(yīng)用于很多應(yīng)用,它對(duì)縱向相干性和掩模對(duì)準(zhǔn)的限制較寬松,并且能夠在單個(gè)樣本曝光中進(jìn)行雙向相位對(duì)比圖像。不幸的是,單掩模邊緣照明裝置的折射靈敏度以及因此的信噪比受到探測器偽影的限制。此外,它需要多次曝光才能進(jìn)行暗場成像 - 一種能夠?qū)π∮趫D像分辨率的微結(jié)構(gòu)進(jìn)行成像的方法。文章建議在單個(gè)掩模成像設(shè)置中使用帶有 Timepix3 像素讀出芯片的 Advapix 探測器,以提高相位對(duì)比圖像中的信噪比。這是利用 Timepix3 芯片同時(shí)獲取單光子事件的快速到達(dá)時(shí)間和超閾值測量的能力來實(shí)現(xiàn)的,這使得單個(gè)光子的子像素識(shí)別成為可能。在本文中,我們證明與傳統(tǒng)采集方法相比,使用單光子的亞像素識(shí)別可以將信噪比提高至少 67±5%。從而可以顯著減少所需的樣品劑量。這表明使用 Timepix3 芯片改進(jìn) X 射線相襯成像具有很大的潛力。此外結(jié)果證明了,在單個(gè)掩模邊緣照明設(shè)置中,使用Timepix3在單個(gè)樣本曝光中進(jìn)行暗場成像的可能性。
X-ray phase contrast imaging provides a method to distinguish materials with similar density and effective atomic number, which otherwise would be difficult using conventional X-ray absorption contrast. In recent years, multiple methods have been developed to acquire X-ray phase contrast images using incoherent laboratory sources. The single mask edge illumination setup has been demonstrated as a possible candidate for large scale applications due to its relaxed restrictions on longitudinal coherence and mask alignment, and for its ability to do bi-directional phase contrast images in a single sample exposure. Unfortunately, the single mask edge illumination setup’s refraction sensitivity, and thereby signal to noise, is limited by detector artifacts. Furthermore, it requires multiple exposures to perform dark-field imaging, a method that enables imaging of micro-structures smaller than the image resolution. We propose using an Advapix detector with Timepix3 pixel-readout chip in a single mask imaging setup to improve signal to noise ratio in phase contrast images. This is achieved using the Timepix3 chip’s ability to simultaneously acquire fast time of arrival and time over threshold measurement of single photon events, which enables sub-pixel identification of individual photons. In this paper, we demonstrate that signal to noise ratio can be improved by at least 67± 5 % using subpixel identification of single photons compared to conventional acquisitions methods. Thereby the required sample dose can be reduced considerably. This shows that there is a great potential in using Timepix3 chip to improve x-ray phase contrast imaging. Further, the results indicate the possibility for dark field imaging in a single sample exposure using Timepix3 in a single mask edge illumination setup.
原文鏈接:
文中使用的是來自捷克Advacam公司的光子計(jì)數(shù)、混合像素X射線探測器。