Exploiting Sparsity in the Difference Images to Achieve Higher Acceleration Factors in Non-Contrast MRA

Pippa Storey¹, Ricardo Otazo¹, Lazar Fleysher¹, Niels Oesingmann², Ruth P. Lim¹, Vivian S. Lee¹, Daniel K. Sodickson¹

Non-contrast techniques for peripheral MRA exploit the pulsatility of arterial blood flow and involve subtraction of dark-blood images, acquired during fast flow, from bright-blood images, acquired during slow flow. The difference images, which depict the arteries, are sparse, although the source images are not. We show that higher acceleration factors can be achieved by performing subtraction on the raw data, before calculation of the GRAPPA weights, rather than on the final magnitude images. Depiction of large arteries is similar to that achieved with low acceleration factors and standard reconstruction, but depiction of small arteries and fine branch vessels is compromised.