<title>Diffraction-enhanced imaging: improved contrast and lower dose x-ray imaging</title>

Abstract

Conventional x-ray imaging relies almost entirely on differences in the absorption of x-rays between tissues to produce contrast. While these differences are substantial between bone and soft tissue, they are very small between different soft tissue types resulting in poor visualization of soft tissues. Diffraction enhanced imaging (DEI) is currently in development by several groups as a new imaging modality that exploits information contained within the x- ray scattering distribution at low angles. We have used the SYRMEP beam line at the Elettra Synchrotron facility in Trieste, Italy to image a variety of tissue specimens, together with several phantoms. Mono-energetic photons in the range 17 keV to 25 keV were used with an analyzer crystal which diffracted the x-rays onto a detector. We have obtained some spectacular images which display remarkable contrast and resolution. The images can be processed to separate the pure absorption and pure refraction effects in a quantitative manner. These images demonstrate that DEI provides tissue morphology information not accessible with conventional radiographic imaging. The contrast caused primarily by refraction as the x-ray passes from one tissue type to another in the specimen is evident. Since x-ray refraction is much less energy dependent than absorption there is considerable potential for extremely low dose imaging. We believe that the potential of this technique is considerable and we present dat to illustrate the quality of the images.