Quantitation of intrinsic magnetic susceptibility-related effects in a tissue matrix. Phantom study

A theoretical background and experimental method that allows a separation of intrinsic, tissue-matrix-specific magnetic-field inhomogeneity effects from both macroscopic (large compared with voxel dimensions) and microscopic (on the order of molecular dimensions) inhomogeneities is proposed. Such separation allows one to take full advantage of these tissue-matrix-specific magnetic field inhomogeneity effects to extract information about tissue structure. A method to measure the volume fraction occupied by the susceptibility-perturbing component in a tissue matrix, the R2' relaxation rate constant, and the susceptibility difference between the bulk component and the susceptibility-perturbing component in a tissue matrix has been developed and tested on phantoms. This method offers the potential to assess a variety of tissue parameters, including cerebral blood volume, blood volume and blood oxygenation-level changes in functional MRI, the structure of trabecular bone, and other physiologically important issues.