Adiabatic Inversion Pulses for Myocardial T1 Mapping

PurposeTo evaluate the error in T1 estimates using inversion-recovery-based T1 mapping due to imperfect inversion and to perform a systematic study of adiabatic inversion pulse designs in order to maximize inversion efficiency for values of transverse relaxation (T2) in the myocardium subject to a peak power constraint. MethodsThe inversion factor for hyperbolic secant and tangent/hyperbolic tangent adiabatic full passage waveforms was calculated using Bloch equations. A brute-force search was conducted for design parameters: pulse duration, frequency range, shape parameters, and peak amplitude. A design was selected that maximized the inversion factor over a specified range of amplitude and off-resonance and validated using phantom measurements. Empirical correction for imperfect inversion was performed. ResultsThe tangent/hyperbolic tangent adiabatic pulse was found to outperform hyperbolic secant designs and achieve an inversion factor of 0.96 within 150 Hz over 25% amplitude range with 14.7 mu T peak amplitude. T1 mapping errors of the selected design due to imperfect inversion was approximate to 4% and could be corrected to <1%. ConclusionsNonideal inversion leads to significant errors in inversion-recovery-based T1 mapping. The inversion efficiency of adiabatic pulses is sensitive to transverse relaxation. The tangent/hyperbolic tangent design achieved the best performance subject to the peak amplitude constraint. Magn Reson Med 71:1428-1434, 2014. (c) 2013 Wiley Periodicals, Inc.