Multiband echo-shifted echo planar imaging.

Abstract

To propose the technique multiband echo-shifted (MESH) echo planar imaging (EPI), which combines the principles of echo-shifted acquisition for two-dimensional multislice EPI, with both in-plane and multiband acceleration by means of partial parallel imaging techniques. MESH EPI is suitable for functional MRI (fMRI) in situations where there is sufficient time to insert an additional EPI readout in the dead time between slice selection and the standard EPI readout. In such situations, MESH EPI can further accelerate data acquisition compared with standard multiband techniques. The method is particularly well suited for low static magnetic field strengths and lower spatial resolutions. We compared MESH with multiband and standard EPI with temporal signal-to-noise ratio (tSNR) measurements and resting state fMRI data. Results obtained at 1.5 T from healthy subjects revealed that the additional gradient switching did not additionally affect time course SNR over and above the reduction inherent to multiband imaging. Functional results were qualitatively similar between methods. MESH was not affected by the tSNR reduction and echo shifting gradients. The MESH data were acquired at a factor 2 or 3 faster than corresponding multiband acquisitions for echo shift factors of 1 and 2, respectively. MESH can offer further acceleration of image acquisition for fMRI at no loss in sensitivity. Magn Reson Med 77:1981-1986, 2017. © 2016 International Society for Magnetic Resonance in Medicine.