Different magnetization transfer effects exhibited by the short and long T2 components in human brain

Magnetization transfer ratios (MTRs) were measured separately for the two T2 components in white matter. For both binomial and off‐resonance sinc MT pulses, the MTR was larger for the short T2 component than for the long T2 component. This differential MT effect disappeared for delays between the MT pulse and the multi‐echo pulse sequence longer than 200 msec, indicating exchange between the two components. When using the sinc MT pulse, the MTR for the short T2 component was similar for different white matter structures, whereas it varied for different white matter structures when using the binomial pulse—a phenomenon attributed to direct saturation. When the sinc pulse frequency was brought closer to resonance, MTRs in white matter and doped water phantoms increased for both components but more so for the shorter T2 component. This behavior was consistent with a Bloch equation model of direct saturation. Magn Reson Med 44:860–866, 2000. © 2000 Wiley‐Liss, Inc.

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