“…The study of optical imaging is a subject of fundamental and technological importance in many research fields. − Of particular interest is that X-ray imaging becomes one of the most important analytical approaches that has been extensively used for medical diagnosis since the discovery of X-rays by Wilhelm Roentgen in 1895. , Owing to the high penetrating ability of X-rays and the various X-ray absorption in different tissues, medical X-ray imaging offers a powerful tool to visualize the internal biological tissues and structures of patients for disease detection and diagnosis. , This X-ray imaging technique relies on the inherent contrast from different X-ray attenuations in tissues to provide useful information on the structural changes for noninvasive monitoring of the disease process. To date, anatomical organs such as skeleton and lungs are easily detected by X-ray imaging due to their large differences in X-ray absorption among bone, tissue, and air. , However, it is often challenging to identify subtle changes in soft tissues, especially for tiny tumors and blood vessels.…”