A technique for improving tag contrast persistence in SSFP MRI imaging using adaptive flip angle

Steady state free precession (SSFP) proved to be an efficient fast MR imaging technique due to its short acquisition time and high SNR. Myocardium tagging can be combined with SSFP, so that the deformation of tag lines allows for measurement of myocardial wall motion. However, at later imaging time, the tagging contrast deteriorates, which makes it harder to track the tag lines. We introduce a new technique that adaptively adjusts the flip angle at each RF pulse in order to keep the tagging contrast constant, and hence maintain the tag contrast to noise ratio (Tag-CNR) throughout the imaging period. A computer simulation was done to validate and compare between the tagging contrast with SSFP and that of spoiled gradient echo (SPGR), where the tagging contrast is made constant during the cine sequences in both methods. Preliminary results show potential superiority of SSFP in yielding higher contrast than SPGR.