Analysis of on‐ and off‐resonance magnetization transfer techniques

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Abstract
Three methods of performing magnetization transfer (MT) MR imaging ere emlyzed: (a) off‐resonance continuous wave, (b) off‐rceonance shaped pulses, end (c) on‐resonance binomial pulses. With two‐pool Bloch‐model simulations., signal levels from “MT active” spin systems were calculated. with reference to direct saturation of “MT inactive” systems. allowing calculation of contrast due to MT. Simulations demonstrate several trends with variation of excitation amplitude and Offret fiequency for the off‐resoname methods and with variation of excitation emplitude end pulse shape „order”︁ for binomial pulses. The simulations show that nominally optimized versions of each of these approaches provide essentially equivalent contrast at a given level of applied MT power, contrary to previous claims. Experiments with an MT‐inactive phentom, with a whole‐body syetem, show results with off‐ rewnence pulses to be in good agreement with simulations. whereas binomiel‐ pulse experiments show anomalously large direct saturation.