Optimized contrast-to-noise ratio efficiency of Magnetization Transfer brain imaging at 0.55T

Motivation: Magnetization Transfer (MT) is an important contrast in neuroimaging that is typically limited by specific absorption rate (SAR) safety limits. Goal(s): Improve contrast-to-noise ratio (CNR) efficiency of MT ratio (MTR) mapping in the brain at 0.55T where SAR constraints are less restrictive and longer, more efficient readouts are feasible. Approach: Sequence parameters were fully constrained by hardware limits and optimized for maximum CNR efficiency of MTR between white and gray matter. A range of repetition times (TR) were explored. Results: In-vivo 3D MTR maps showed improved CNR efficiency with longer TR, with optimized sequence parameters operating at the limits of the system. Impact: Efficient acquisitions at lower field resolves the two greatest difficulties of deploying Magnetization Transfer Ratio images in the clinic, namely scan time and SAR concerns.