Magnetic Resonance Line Shape of Water as a Probe of the Structure of Biological Tissue

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The NMR line shape of water in magnetically heterogeneous tissues is known to deviate from the Lorentzian shape. A novel description was proposed recently using the effective medium theory, which has been originally developed within condensed matter physics to describe transport in disordered media. The central quantity in this description is the self-energy part of the medium- averaged propagator. In the present MRI context, it can be interpreted as a transverse relaxation rate that depends on the frequency in the spectral domain. This dependence can be used as a probe of tissue structure yielding its characteristic correlation length and a measure of the dis- order strength. The first application to blood water spectroscopy demonstrated the potential of the method. The present project aims at using this potential to develop and verify methods for investigating cell-related heterogeneous magnetic structure in vivo. The method will be developed and optimized in blood as a relative simple and well studied system. The method will then be extended for measurements in suspensions of other cell species. First pilot applications of the method would be characterisation of tumour cellular structure in animal model and detection of parameters of the ferritin distribution in the normal human brain. These applications are aimed at exploiting the method potential and motivating future studies.