PURPOSE: To optimize and validate a fully-integrated version of modified 
Look-Locker inversion-recovery (MOLLI) for clinical single-breathhold cardiac T1 
mapping.
MATERIALS AND METHODS: A MOLLI variant allowing direct access to all pulse 
sequence parameters was implemented on a 1.5T MR system. Varying four critical 
sequence parameters, MOLLI was performed in eight gadolinium-doped agarose gel 
phantoms at different simulated heart rates. T1 values were derived for each 
variant and compared to nominal T1 values. Based on the results, MOLLI was 
performed in midcavity short-axis views of 20 healthy volunteers pre- and 
post-Gd-DTPA.
RESULTS: In phantoms, a readout flip angle of 35 degrees , minimum TI of 100 
msec, TI increment of 80 msec, and use of three pausing heart cycles allowed for 
most accurate and least heart rate-dependent T1 measurements. Using this pulse 
sequence scheme in humans, T1 relaxation times in normal myocardium were 
comparable to data from previous studies, and showed narrow ranges both pre- and 
postcontrast without heart rate dependency.
CONCLUSION: We present an optimized implementation of MOLLI for fast T1 mapping 
with high spatial resolution, which can be integrated into routine imaging 
protocols. T1 accuracy is superior to the original set of pulse sequence 
parameters and heart rate dependency is avoided.