Accurate MRF T2 in structured materials at 0.55T using MT-suppressed excitations

Motivation: Magnetization transfer (MT) effects are known to cause underestimation of T2 in structured materials when using magnetic resonance fingerprinting (MRF). This effect and resulting T2 bias is exacerbated at lower field strength. Goal(s): To improve the accuracy of 0.55T FISP MRF T2 maps in structured material (e.g. white matter) without compromising precision. Approach: We replaced slab-selective RF excitations with non-selective RF excitations in FISP-MRF. We evaluated the approach with two pulse durations on 1 healthy volunteer against (slow) reference measurements. Results: The use of non-selective RF excitations reduced white matter T2 bias from ~40% to <10%. Impact: The use of non-selective RF excitations substantially reduces MT effects, which mitigates biases in T2 maps estimated using FISP-MRF. This is essential for the application of MRF at low field strengths in structured materials such as white matter.