Saturation pulse design for quantitative myocardial T(1) mapping

BACKGROUND: Quantitative saturation-recovery based T(1) mapping sequences are less sensitive to systematic errors than the Modified Look-Locker Inversion recovery (MOLLI) technique but require high performance saturation pulses. We propose to optimize adiabatic and pulse train saturation pulses for quantitative T(1) mapping to have <1 % absolute residual longitudinal magnetization (|M(Z)/M(0)|) over ranges of B(0) and [Formula: see text] (B(1) scale factor) inhomogeneity found at 1.5 T and 3 T. METHODS: Design parameters for an adiabatic BIR4-90 pulse were optimized for improved performance within 1.5 T B(0) (±120 Hz) and [Formula: see text] (0.7–1.0) ranges. Flip angles in hard pulse trains of 3–6 pulses were optimized for 1.5 T and 3 T, with consideration of T(1) values, field inhomogeneities (B(0) = ±240 Hz and [Formula: see text] =0.4–1.2 at 3 T), and maximum achievable B(1) field strength. Residual M(Z)/M(0) was simulated and measured experimentally for current standard and optimized saturation pulses in phantoms and in-vivo human studies. T(1) maps were acquired at 3 T in human subjects and a swine using a SAturation recovery single-SHot Acquisition (SASHA) technique with a standard 90°-90°-90° and an optimized 6-pulse train. RESULTS: Measured residual M(Z)/M(0) in phantoms had excellent agreement with simulations over a wide range of B(0) and [Formula: see text] . The optimized BIR4-90 reduced the maximum residual |M(Z)/M(0)| to <1 %, a 5.8× reduction compared to a reference BIR4-90. An optimized 3-pulse train achieved a maximum residual |M(Z)/M(0)| <1 % for the 1.5 T optimization range compared to 11.3 % for a standard 90°-90°-90° pulse train, while a 6-pulse train met this target for the wider 3 T ranges of B(0) and [Formula: see text] . The 6-pulse train demonstrated more uniform saturation across both the myocardium and entire field of view than other saturation pulses in human studies. T(1) maps were more spatially homogeneous with 6-pulse train SASHA than the reference 90°-90°-90° SASHA in both human and animal studies. CONCLUSIONS: Adiabatic and pulse train saturation pulses optimized for different constraints found at 1.5 T and 3 T achieved <1 % residual |M(Z)/M(0)| in phantom experiments, enabling greater accuracy in quantitative saturation recovery T(1) imaging. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12968-015-0187-0) contains supplementary material, which is available to authorized users.