Feasibility of k-t BLAST For BOLD fMRI With a Spin-Echo Based Acquisition at 3 T and 7 T

Objectives:This study tested the feasibility of applying k-t BLAST to blood oxygen level dependent functional MRI of the brain at 3 Tesla (T) and at 7 T. Shorter echo train lengths, achieved through the application of k-t BLAST, are expected to counteract increased sensitivity to inhomogeneities in B0 at higher magnetic field strengths, especially in echo planar images, and reduce the relatively long acquisition times and high RF power deposition in spin-echo based methods. Materials and Methods:k-t BLAST was combined with displaced UFLARE at 3 T and 7 T. Temporal and spatial fidelity of k-t BLAST were investigated using a test object, in which localized variations in signal intensity mimic activation-induced signal changes. fMRI was performed using typical box-car design finger tapping. In a separate analysis full k-space data were decimated to simulate k-t BLAST acquisitions and compare results with the fully sampled data, thereby avoiding physiological and noise differences between acquisitions. Results:Activation can be detected at under-sampling factors as high as 16, whereas appropriately reconstructed data, under-sampled at factors below 8 entail insignificant loss of sensitivity and considerable reductions in acquisition times and RF power deposition. Conclusions:k-t BLAST is compatible with fMRI acquisitions and opens up possibilities including distortion-free T2*-weighted blood oxygen level dependent fMRI with displaced UFLARE at high magnetic field strengths.