X-ray phase imaging reaching clinical uses

•Drawback of conventional X-ray radiography overcome by using X-ray phase contrast.•Effective for materials consisting of low-Z element, such as polymers and biological soft tissues.•Quantitative images mapping refraction and scattering in addition to attenuation.•Development initially at synchrotron radiation facilities expanding at hospitals.•Apparatus using grating interferometry in operation for clinical studies with patients in hospitals. X-ray phase imaging that uses the phenomena of X-ray refraction and scattering to generate image contrast has the potential to overcome the drawback of conventional X-ray radiography in observing biological soft tissues. After its dawn at synchrotron radiation facilities 30 years ago, the development of X-ray phase imaging is expanding to hospitals by grating-based phase-imaging approaches available with a conventional X-ray tube. In this review, after introducing the physical advantages and methodological details of X-ray phase imaging, recent trials of instrumentation in hospitals for diagnoses of rheumatoid arthritis and chronic obstructive pulmonary disease are introduced.