Accelerated 1 H MRSI using randomly undersampled spiral‐based k‐space trajectories

Purpose To develop and evaluate the performance of an acquisition and reconstruction method for accelerated MR spectroscopic imaging (MRSI) through undersampling of spiral trajectories. Theory and Methods A randomly undersampled spiral acquisition and sensitivity encoding (SENSE) with total variation (TV) regularization, random SENSE+TV, is developed and evaluated on single‐slice numerical phantom, in vivo single‐slice MRSI, and in vivo three‐dimensional (3D)‐MRSI at 3 Tesla. Random SENSE+TV was compared with five alternative methods for accelerated MRSI. Results For the in vivo single‐slice MRSI, random SENSE+TV yields up to 2.7 and 2 times reduction in root‐mean‐square error (RMSE) of reconstructed N‐acetyl aspartate (NAA), creatine, and choline maps, compared with the denoised fully sampled and uniformly undersampled SENSE+TV methods with the same acquisition time, respectively. For the in vivo 3D‐MRSI, random SENSE+TV yields up to 1.6 times reduction in RMSE, compared with uniform SENSE+TV. Furthermore, by using random SENSE+TV, we have demonstrated on the in vivo single‐slice and 3D‐MRSI that acceleration factors of 4.5 and 4 are achievable with the same quality as the fully sampled data, as measured by RMSE of reconstructed NAA map, respectively. Conclusion With the same scan time, random SENSE+TV yields lower RMSEs of metabolite maps than other methods evaluated. Random SENSE+TV achieves up to 4.5‐fold acceleration with comparable data quality as the fully sampled acquisition. Magn Reson Med 74:13–24, 2015. © 2014 Wiley Periodicals, Inc.