Ek T. Tan1, Seung-Kyun Lee1, Jean-Baptiste Mathieu1, Venkata Veerendranadh Chebrolu2, Dattesh D. Shanbhag2, Matthew A. Bernstein3, John Huston III3, Luca Marinelli1, John F. Schenck1
1Diagnostics and Biomedical Technologies, GE Global Research, Niskayuna, NY, United States; 2Diagnostics and Biomedical Technologies, GE Global Research, Bangalore, India; 3Radiology, Mayo Clinic, Rochester, MN, United States
A head-only MRI system can have cost and performance advantages, especially in diffusion imaging. However, a dedicated head-only gradient coil tends to have a greater gradient field nonlinearity (GN) compared to a conventional whole-body gradient coil optimized for body imaging. This nonlinearity results in a larger spatial variation of the diffusion-encoding b-value. Diffusion imaging using a dedicated, head-only gradient coil without nonlinearity correction was found to produce significant, spatially-varying b-values that would result in highly inaccurate diffusion-weighted images, ADC and FA. However, the inaccuracies were correctable with GN correction employing 5th-order spherical harmonics. These results will be of interest in quantitative stroke and oncology imaging.