MRI provides the capability for in vivo measurement of a variety of physiological properties, such as NMR relaxation times, diffusion constants, and blood flow. In our group, new MRI methods are being developed in order to obtain more accurate measurements and to estimate quantities not probed by existing techniques.

A major part of our effort has been to establish improved mathematical models for the effect of microscopic magnetic field inhomogeneities on NMR signal decay. Microscopic field inhomogeneities are, for example, generated by iron-rich oligodendrocytes in the brain, hemosiderin clusters in the liver, and extracellular paramagnetic contrast agents. By applying these models to data obtained with specialized pulse sequences, new approaches for quantifying iron in the brain and the liver are being explored. These may be important for assessing neurological disorders, including Alzheimer?s and Parkinson?s diseases, and iron overload pathologies, such as hereditary hemochromatosis and thalassemia major.

One particular method, known as magnetic field correlation (MFC) imaging, utilizes asymmetric spin echo pulse sequences to estimate a correlation function that characterizes the field inhomogeneities within a tissue. This technique is currently being exploited to study the pattern of iron deposition in normal and diseased brain using 3 T scanners.

Other active projects include the quantifying of non-Gaussian water diffusion and microvessel densities by means of MRI. Quantification of water diffusion is useful for evaluating stroke, and quantification of microvessel density is useful for the study of tumor angiogenesis.