Magnetization Transfer Contrast

Magnetization transfer techniques use an off resonance RF pulse to saturate protons in macromolecules and water molecules that are bound to macromolecules and are normally not visible due to their very short T2* relaxation times (See Figure). During the pulse sequence, the saturated protons may enter the free pool of protons, primarily water, or may transfer their magnetization to free water protons. The effect of this is to cause a decrease in the MR visible signal in areas of macromolecules effected by magnetization transfer. This provides an additional source of tissue contrast for imaging, particularly of the brain. One use of magnetization transfer is to reduce the signal from brain tissue during MR angiography, thereby improving vessel delineation. Areas of demyelinaton on T2-weighted images and areas on enhancement with gadolinium contrast agents on T1-weighted images way be more visible with magnetization transfer techniques.