Enhancement of functional MRI signal at high-susceptibility regions of brain using simultaneous multiecho multithin-slice summation imaging technique

Abstract

Purpose: To increase temporal-signal-to-noise ratio (tSNR) and blood oxygen level-dependent (BOLD) sensitivity at high-susceptibility regions of the brain by means of a simultaneous multiecho multithin-slice summation imaging technique. Materials and Methods: The simultaneous multislice (SMS) technique was implemented with multiecho (SMSME) and multiecho with thin-slice summation (SMSME-thin) at 3T. Multiecho data were summated based on the local apparent T*2 weighting factor. Ten healthy subjects were studied for the whole brain activation by breath-holding. The tSNR values and the number of activated pixels acquired with SMSME and SMSME-thin were compared with those acquired with the conventional gradient-echo EPI in multiple brain regions. Results: SMS methods accelerated imaging time by 5-fold as compared with the conventional method, resulting in the acquisition of three echoes and four thin-slices during the same TR of 2.5 seconds. At high-susceptibility regions, including the amygdala, inferior and middle temporal, and anterior frontal lobes, SMSME increased tSNR values by up to ∼80% and BOLD activation by up to ∼20% (paired t-test, P < 0.05). SMSME-thin further increased values as compared with SMSME (∼45% for tSNR and ∼20% for activation, P < 0.05). Conclusion: The SMSME-thin imaging technique enhanced the temporal-signal-to-noise ratio and functional activation at high susceptibility regions of the brain. J. Magn. Reson. Imaging 2016;44:478–485.