Feasibility study of x-ray diffraction computed tomography for medical imaging.

A feasibility study of soft-tissue imaging based on x-ray wide-angle diffraction contrast has been performed at the medical beamline of the European Synchrotron Radiation Facility (ESRF). The technique employs computed-tomography algorithms to reconstruct from one data set the spatial distribution of several tissues differentiated by their diffraction properties. Radial diffraction profiles are measured in parallel projections from the sample and decomposed into material-selective weighting factors, which form the sinograms for the reconstructions. Attenuation effects--inherent in imaging techniques using scattered radiation--are efficiently corrected for by a ray-tracing method applied to the corresponding absorption image. Images of 7 cm diameter samples composed of fat, bone and muscle were generated at 60 and 80 keV x-ray energy. The highest surface-absorbed dose was 24 mGy, but substantial contrast could still be obtained at 7 mGy, indicating potential applicability in medical imaging. The dominant noise contribution in the images stems from the detection system, pointing to a possible decrease in the surface-absorbed dose for an optimized system of more than a factor of 2.