Ultra-low-field Magnetization Transfer Imaging with Low SAR

At high field, magnetization transfer (MT) imaging suffers from the high specific absorption ratio (SAR) issue due to the usage of high power off-resonance MT RF pulses, and on-resonance saturation caused by B0 field inhomogeneity. At ultra-low-field (ULF), the low SAR and low absolute B0 inhomogeneity (in Hz) greatly facilitates the application of strong and versatile MT pulses without the confounding on-resonance saturation in practice. We demonstrate brain MT imaging at ULF first the first time using a 0.055 Tesla MRI platform with an extremely low SAR.