CNR improvement of MP2RAGE from slice encoding directional acceleration

Abstract

Purpose: While MP2RAGE shows the potential to generate B-1 insensitive T-1 contrast, the long TR of MP2RAGE (>= 6 s at 7 T) is essential to provide the large dynamic range of apparent T-1 relaxation for dual inversion time acquisitions. We present a 2 direction (2D) accelerated MP2RAGE, which provides an increased flip angle while maintaining similar dynamic recovery as 1D accelerated MP2RAGE. Method: Simulations were conducted to optimize 2D accelerated MP2RAGE parameters and healthy subjects were scanned with 1D and 2D accelerated MP2RAGE at 7 T. Images were compared visually and contrast to noise (CNR) between brain tissues was measured. Result: Simulations showed that CNR is primarly determined by the TR, followed by the number of the first partition encoding steps in MP2RAGE. Keeping TR constant, a smaller number of partition encoding steps increases the achievable maximal CNR. In-vivo 2D MP2RAGE improves CNR between white and gray matters by 9% when compared to 1D accelerated MP2RAGE with identical voxel size. Conclusion: We presented 2D accelated MP2RAGE at 7 T with the increased flip angle. We show that this leads to CNR improvement, and consequently a reduction of scan time to be compared to 1D accelerated MP2RAGE. (C) 2016 Elsevier Inc. All rights reserved.