New Frontiers in X-ray Imaging
M. Wernick, J. Brankov, M.A. Anastasio, Y. Yang, D. Chapman (U. Saskatchewan, C. Muehleman (Rush Med. Coll.), E. Pisano (UNC-Chapel Hill), C. Parham (UNC-Chapel Hill), Z. Zhong (Brookhaven Natl. Lab.), M. Yaffe (U. Toronto)
Conventional x-ray imaging (radiography) is the most widely used diagnostic imaging technique in medicine, but it has serious and well-known shortcomings, which are driving the development of innovative alternatives for mammography and other soft-tissue imaging applications, such as cartilage imaging. Our group has been developing an x-ray imaging approach called multiple-image radiography (MIR), which shows promise as a potential alternative to conventional x-ray imaging (radiography). Whereas conventional radiography produces just one image, depicting absorption effects, MIR simultaneously produces three images, showing separately the effects of absorption, refraction, and ultra-small-angle x-ray scattering. The latter two effects are caused by refractive-index variations in the object, which yield fine image details not seen in standard radiographs. MIR has the added benefits of dramatically lessening radiation dose, virtually eliminating scatter degradation, and lessening the importance of compressing the breast during imaging. Like computed tomography (CT), MIR is a computed imaging technique, in which the images are not directly observed, but rather computed algorithmically. This project is sponsored by NIH/NCI.
In the past decade, radiation therapy has undergone a revolution. Advances in treatment delivery equipment, imaging systems, and treatment planning capabilities, have resulted in treatment fields becoming smaller and more tightly conformed to the tumor. These new treatments have become much more susceptible to errors in patient positioning, caused either by set-up errors or organ motion. Thus, there is an increasing need for imaging methods to identify the tumor volume within the patient before the treatment delivery. We are developing and investigating dose-efficient tomographic imaging methods based on the local tomography paradigm that will facilitate patient positioning verification in conformal radiation therapy treatments. We are collaborating with clinical and basic science faculty at The University of Chicago Medical Center on this project. This project is sponsored by NIH/NCI and the Whitaker Foundation.
Characterizing angiogenesis and microvascular architecture in biological systems is of tremendous value in a wide range of biological fields such as tissue engineering, cancer, rehumatoid arthritis, and ischemic heart disease research. The ability to perform such characterizations efficiently and effectively is hindered, in large part, by the available imaging modalities. We are currently developing and investigating reconstruction algorithms for X-ray phase-contrast microtomography, and evaluating their use for reconstructing the microvascular structure of biological tissues and tumors. This project is sponsored by NIH/NIBIB.
Diffraction tomography (DT) is an imaging technique for reconstructing the complex-valued refractive index distribution of an object. An undesirable characteristic of DT is that it requires measurement of the amplitude and phase of the transmitted wavefield. Phase measurements generally present considerable difficulties in optical and X-ray applications. Recently, a new theory of intensity DT (I-DT) has been proposed that circumvents the need to make explicit wavefield phase measurements. We are analytically and numerically investigating the I-DT reconstruction theory and generalizing it to accommodate scanning geometries that are of practical importance. Applications of I-DT to optical microscopy and coherent X-ray imaging are being explored actively.