Slice-selective adiabatic magnetization T₂ -preparation (SAMPA) for efficient T₂ -weighted imaging at ultrahigh field...

At high field, T₂ -weighted (T₂ w) imaging is limited by transmit field inhomogeneity and increased radiofrequency power deposition. In this work, we introduce SAMPA (Slice-selective Adiabatic Magnetization T₂ PrepAration) and demonstrate its use for efficient brain T₂ w imaging at 7 Tesla (T).

SAMPA was designed by subsampling an optimized B₁ insensitive rotation (BIR4) waveform with small tip angle linear subpulses. To perform T₂ w imaging, SAMPA was inserted before a fast gradient echo acquisition. The off-resonance behavior, B₁ robustness, and slice selectivity of the novel T₂ preparation module were analyzed using Bloch simulations. The performance of SAMPA for T₂ w imaging was demonstrated in phantom experiments as well as in the brains of healthy volunteers at 7T.

Based on simulations, the proposed design operates at peak B₁ of 15 μT and higher, within a 400 Hz bandwidth. T₂ values were in strong agreement with spin echo-based T₂ mapping in phantom experiments. Whole brain, interleaved multislab three-dimensional imaging could be acquired with 0.8 mm³ isotropic resolution in 5:36 min per T₂ weighting.

Compared with previous adiabatic T₂ preparation techniques, SAMPA allows for slice-selectivity, which can lead to efficient and robust acquisitions for T₂ w imaging at high field. Magn Reson Med 76:1741-1749, 2016. © 2015 International Society for Magnetic Resonance in Medicine.