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Phase contrast enhancement of x-ray mammography: a design study

Lookup NU author(s): Dr Colin Kotre, Ian Birch


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This paper explores the application to mammography of phase contrast produced by variations in x-ray refractive index. As a spatially coherent x-ray beam propagates through an x-ray transparent medium, the phase of the incident wavefront becomes modified in a manner related to the electron density of the medium. The resulting phase gradient across the wavefront is equivalent to a small change in direction of the propagation of the wave. For a general object, the change in propagation direction will vary from point to point depending on the structures within the object. The net effect can be recorded in a radiographic image using an appropriate geometry to produce the visual appearance of edge enhancement at interfaces between materials with differing x-ray refractive indices. Normally these materials will also have differences in attenuation coefficient, so the overall effect is to increase the visibility of interfaces between materials. It is proposed that mammographic images can be subtly enhanced by the use of phase contrast information to overcome some of the known limitations of the imaging process whilst leaving the gross radiological appearance of the images substantially unchanged. The design trade-offs required to utilize phase contrast information were investigated using a conventional mammographic x-ray generator and film-screen system. The Leeds TORMAM mammographic image quality test object was then used to demonstrate a considerable improvement in image quality for the phase contrast enhanced images over those produced in the conventional geometry with no increase in radiation dose to the patient. The results are discussed in terms of their possible practical application.

Publication metadata

Author(s): Kotre CJ, Birch IP

Publication type: Article

Publication status: Published

Journal: Physics in Medicine and Biology

Year: 1999

Volume: 44

Issue: 11

Pages: 2853-2866

Print publication date: 01/11/1999

ISSN (print): 0031-9155

ISSN (electronic): 1361-6560

Publisher: Institute of Physics Publishing Ltd.