Medical phase contrast x-ray imaging: current status and future prospects.

The exploitation of phase contrast appears to offer the tantalising possibility of creating the biggest change in medical x-ray imaging since the invention of computed tomography. A considerable number of experiments performed by researchers across four continents have produced some extraordinary images. These images have demonstrated greatly enhanced contrast over conventional methods revealing soft tissue discrimination at micron scale resolutions. Contrast improvements can be achieved at doses rather less than those required by conventional x-ray imaging. The use of synchrotrons has revealed the possibilities offered by these techniques but unfortunately the application of these ideas in a clinical context requires that technology be pushed to its limits in a number of areas including x-ray sources, optics and detectors. The current state of the art is reviewed.