Magnetization transfer contrast: Experimental sequence optimization for studies on cerebral white matter

Purpose: A new application for magnetization transfer (MT) MR imaging is the investigation of cerebral white matter. For that a pure Mi effect is desirable. Our purpose was the optimization and testing of an MT sequence for investigations of cerebral white matter. Material and methods: Experimental investigations were performed in phantom material and in 5 wistar rats using various frequency offsets (FO) (200 Hz-30 000 Hz). Relative signal suppression (rSS) for the phantom material and for callosal white matter of the rat was calculated. The optimized sequence was tested in 25 healthy volunteers. Results: A relatively pure MT effect was achieved with FO > 4000 Hz. rSS for cerebral white matter structures was generally higher than rSS Mr cerebral gray matter structures. rSS for cerebral white matter structures ranged from 45-50%. Conclusion: We present a fast MT sequence with high rSS for cerebral white matter and a relatively pure MT effect. Owing to the high rSS-values we expect that this sequence improves differentiation of cerebral white matter lesions. Because of the confusing variety of MT sequence currently described in the literature we believe that standard parameters should be defined to make published results comparable.