B0 and B1 inhomogeneities in the liver at 1.5 T and 3.0 T

Purpose The purpose of this work is to characterize the magnitude and variability of B-0 and B-1 inhomogeneities in the liver in large cohorts of patients at both 1.5 T and 3.0 T. Methods Volumetric B-0 and B-1 maps were acquired over the liver of patients presenting for routine abdominal MRI. Regions of interest were drawn in the nine Couinaud segments of the liver, and the average value was recorded. Magnitude and variation of measured averages in each segment were reported across all patients. Results A total of 316 B-0 maps and 314 B-1 maps, acquired at 1.5 T and 3.0 T on a variety of GE Healthcare MRI systems in 630 unique exams, were identified, analyzed, and, in the interest of reproducible research, de-identified and made public. Measured B-0 inhomogeneities ranged (5th-95th percentiles) from -31.7 Hz to 164.0 Hz for 3.0 T (-14.5 Hz to 81.3 Hz at 1.5 T), while measured B-1 inhomogeneities (ratio of actual over prescribed flip angle) ranged from 0.59 to 1.13 for 3.0 T (0.83 to 1.11 at 1.5 T). Conclusion This study provides robust characterization of B-0 and B-1 inhomogeneities in the liver to guide the development of imaging applications and protocols. Field strength, bore diameter, and sex were determined to be statistically significant effects for both B-0 and B-1 uniformity. Typical clinical liver imaging at 3.0 T should expect B-0 inhomogeneities ranging from approximately -100 Hz to 250 Hz (-50 Hz to 150 Hz at 1.5 T) and B-1 inhomogeneities ranging from approximately 0.4 to 1.3 (0.7 to 1.2 at 1.5 T).