基于级联光栅的X射线相衬成像实验研究

Experimental Study of X-ray Phase Contrast Imaging Based on Cascaded Grating

为避免小周期高宽比吸收光栅的制作,提出了由泰伯-劳干涉仪和逆泰伯-劳干涉仪组成的级联光栅X射线相衬成像装置,该装置利用泰伯-劳干涉仪的自成像作为逆泰伯-劳干涉仪的源.通过实验验证了该方法的有效性,得到了成像系统的莫尔条纹和强度振荡曲线.条纹最高对比度为17.4%,随着吸收光栅偏离零点位置,条纹对比度逐渐降低,但是在其位置跨越从-17mm到12mm的范围内,条纹对比度仍保持在10%以上.实验讨论了样品位置对成像灵敏度的影响,结果表明当样品位置靠近相位光栅两侧时,其成像灵敏度最高.本文的研究可应用于生物医学成像的大视场X射线相衬成像系统的设计.

A cascade interferometer for X-ray phase-contrast imaging composed by a Talbot-Lau interferometer and an inverse Talbot-Lau interferometer was implemented,which the self-image of Talbot-Lau interferometer being used as the source of the inverse Talbot-Lau interferometer,with the purpose to avoid the fabrication of small-period high aspect-ratio absorption gratings.Experiments validated the method,while moire fringes and intensity oscillation curves of the imaging system are obtained.The maximum visibility of the fringes was17.4%.With the absorption grating deviating from the zero position,the visibility of the fringes decreased gradually.But it remained above10%,when the position of the absorption grating spaned from-17mm to12mm.And the angular sensitivity as a function of the sample position was discussed.Results show that the highest sensitivity is obtained,when the investigated object is close to the phase grating.This will be useful for designing an X-ray phase-contrast imaging system for applications of biomedical imaging in large field of view.