Background: Chronic obstructive pulmonary disease (COPD) is one of the leading\ncauses of morbidity and mortality worldwide, and emphysema is a common\ncomponent of COPD. Currently, it is very difficult to detect early stage emphysema\nusing conventional radiographic imaging without contrast agents, because the change\nin X-ray attenuation is not detectable with absorption-based radiography. Compared\nwith the absorption-based CT, phase contrast imaging has more advantages in soft\ntissue imaging, because of its high spatial resolution and contrast.\nMethods: In this article, we used diffraction enhanced imaging (DEI) method to get\nthe images of early stage emphysematous and healthy samples, then extract X-ray\nabsorption, refraction, and ultra-small-angle X-ray scattering (USAXS) information from\nDEI images using multiple image radiography (MIR). We combined the absorption\nimage with the USAXS image by a scatter plot. The critical threshold in the scatter plot\nwas calibrated using the linear discriminant function in the pattern recognition.\nResults: USAXS image was sensitive to the change of tissue micro-structure, it could\nshow the lesions which were invisible in the absorption image. Combined with the\nabsorption-based image, the USAXS information enabled better discrimination between\nhealthy and emphysematous lung tissue in a mouse model. The false-color images\ndemonstrated that our method was capable of classifying healthy and emphysematous\ntissues.\nConclusion: Here we present USAXS images of early stage emphysematous and\nhealthy samples, where the dependence of the USAXS signal on micro-structures of\nbiomedical samples leads to improved diagnosis of emphysema in lung radiographs.
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