Dr. L. Dean Chapman BSc, PhD

Medical and Biological Applications of Synchrotron Radiation

My research involves the use of synchrotron radiation and x-ray optics directed to medical and biological problems; specifically in the area of x-ray imaging.

Diffraction Enhanced Imaging.

Diffraction enhanced x-ray imaging is a new technology that makes use of x-ray refraction and scattering as well as absorption in developing image contrast. The new sources of contrast are particularly well suited for soft tissue imaging ­ one of the present difficulties with x-ray imaging. In breast cancer specimens, this method has developed image contrast up to a factor of 33 TIMES higher than conventional x-ray radiography. Present research is directed toward a fundamental understanding of the contrast mechanisms, methods to independently extract the mechanisms into images and computer modeling of tissue systems. Other research involves efforts to develop laboratory based DEI systems with the possible extensions to clinical systems. Some examples of the types of images that can be obtained are shown.

Contrast mechanisms

An area of active research involves measuring and modeling the DEI contrast sources (absorption, refraction and scattering). This involves both a program of theoretical modeling of the contrast and imaging system as well as experimental measurements of contrast from model and tissue systems. In addition, methods of image analysis are being researched. A system that will be dedicated to determining the absorption, refraction and scattering properties of specimens is being developed in the laboratory. In addition this system will be used to explore some of the details of the DEI process that are not possible at the synchrotron.

Applications of DEI

The method was originally developed as part of a synchrotron mammography research program. One area of active research is finding other applications of the technology to soft tissue imaging.

Laboratory DEI

The DEI method makes use of x-ray crystal optics to prepare and analyze the beam that traverses the subject being imaged. The optics severely limit the x-ray fluence from conventional x-ray sources. One area of applied research is the development of a laboratory prototype system that will yield useful information about the possible clinical development of a DEI system. A prototype system has been built at Illinois Institute of Technology; a second unit is planned here that will extend the concepts developed thus far and push the technology close to the needs of a clinical environment in terms of imaging time and image quality.

Application to other types of imaging

The DEI method is a radiographic method that can be extended to other types of existing x-ray imaging. For example, it has been applied to computed tomography in which the reconstructed images are of the object's refraction and absorption properties. The methods that extract scattering are being applied to CT as well (MIR-CT). In addition, the use of DEI with K-edge subtraction imaging is presently being explored as well as other combinations.

X-ray Optics

Most of my background is in x-ray optics for synchrotron radiation research. I, along with Dr. Zhong Zhong , Dr. Cahit Karanfil , and Professor Grant Bunker have developed bent Laue (transmission) crystal devices for fluorescence EXAFS (extended x-ray absorption fine structure) detection. In addition, a number of other applied x-ray optics devices are presently under development primarily for x-ray synchrotron radiation research applications.