Abstract
PURPOSE: To validate single reference variable flip angle (SR-VFA) dynamic T(1) mapping with and without T(2) * correction against inversion recovery (IR) T(1) measurements. METHODS: A custom cylindrical phantom with three concentric compartments was filled with variably doped agar to produce a smooth spatial gradient of the T(1) relaxation rate as a function of angle across each compartment. IR T(1) , VFA T(1) , and B(1) (+) measurements were made on the phantom before rotation, and multi-echo stack-of-radial dynamic images were acquired during rotation via an MRI-compatible motor. B(1) (+) -corrected SR-VFA and SR-VFA-T(2) * T(1) maps were computed from the sliding window reconstructed images and compared against rotationally registered IR and VFA T(1) maps to determine the percentage error. RESULTS: Both VFA and SR-VFA-T(2) * T(1) maps fell within 10% of IR T(1) measurements for a low rotational speed, with a mean accuracy of 2.3% ± 2.6% and 2.8% ± 2.6%, respectively. Increasing rotational speed was found to decrease the accuracy due to increasing temporal smoothing over ranges where the T(1) change had a nonconstant slope. SR-VFA T(1) mapping was found to have similar accuracy as the SR-VFA-T(2) * and VFA methods at low TEs (˜<2 ms), whereas accuracy degraded strongly with later TEs. T(2) * correction of the SR-VFA T(1) maps was found to consistently improve accuracy and precision, especially at later TEs. CONCLUSION: SR-VFA-T(2) * dynamic T(1) mapping was found to be accurate against reference IR T(1) measurements within 10% in an agar phantom. Further validation is needed in mixed fat-water phantoms and in vivo.