METHOD FOR R^*₂ QUANTIFICATION WITH MRI USING CORRECTION FOR MACROSCOPIC MAGNETIC FIELD INHOMOGENEITIES

摘要

A method for measuring transverse relaxation rate, R^*₂, corrected for the presence of macroscopic magnetic field inhomogeneities with a magnetic resonance imaging (MRI) system is provided. The method accounts for additional signal decay that occurs as a result of macroscopic variations in the main magnetic field, B₀, of the MRI system, and also mitigates susceptibility-based errors and introduction of increased noise in the R^*₂ measurements. Image data are acquired by sampling multiple different echo signals occurring at respectively different echo times. A B₀ field inhomogeneity map is estimated by fitting the acquired image data to an initial signal model. Using the estimated field map, a revised signal model that accounts for signal from multiple different chemical species and for signal decay resulting from macroscopic variations in the B₀ field is formed. Corrected R^*₂ values for the different chemical species are then estimated by fitting the acquired image data to the revised signal model.