Half-Fourier single-shot STEAM MRI.

As a high-speed imaging technique based on stimulated echoes single-shot STEAM MRI is insensitive to chemical shift artifacts and magnetic susceptibility differences. The achievable signal-to-noise ratio (SNR) is limited by the fact that high flip angles of the read-out excitation pulses cause a steep decay of the stimulated echo train and therefore degrade the point-spread function of the resulting image. The present work investigates the use of half-Fourier phase encoding which weakens the flip angle constraint by reducing the number of necessary excitations. Single-shot STEAM MRI of the normal human brain at 2.0 T demonstrates that half-Fourier versions either reduce the measurement time by almost a factor of two without sacrificing the SNR or increase the SNR by about 40% while keeping the measurement time constant.