LAUSR

The purpose of the current study was to develop and validate a three‐dimensional (3D) free‐breathing cardiac T1‐mapping sequence using SAturation‐recovery and Variable‐flip‐Angle (SAVA). SAVA sequentially acquires multiple electrocardiogram‐triggered volumes using a multishot spoiled gradient‐echo sequence. The first volume samples the equilibrium signal of the longitudinal magnetization, where a flip angle of 2° is used to reduce the time for the magnetization to return to equilibrium. The succeeding three volumes are saturation prepared with variable delays, and are acquired using a 15° flip angle to maintain the signal‐to‐noise ratio. A diaphragmatic navigator is used to compensate the respiratory motion. T1 is calculated using a saturation‐recovery model that accounts for the flip angle. We validated SAVA by simulations, phantom, and human subject experiments at 3 T. SAVA was compared with modified Look‐Locker inversion recovery (MOLLI) and saturation‐recovery single‐shot acquisition (SASHA) in vivo. In phantoms, T1 by SAVA had good agreement with the reference (R2 = 0.99). In vivo 3D T1 mapping by SAVA could achieve an imaging resolution of 1.25 × 1.25 × 8 mm3. Both global and septal T1 values by SAVA (1347 ± 37 and 1332 ± 42 ms) were in between those by SASHA (1612 ± 63 and 1618 ± 51 ms) and MOLLI (1143 ± 59 and 1188 ± 65 ms). According to the standard deviation (SD) and coefficient of variation (CV), T1 precision measured by SAVA (SD: 99 ± 14 and 60 ± 8 ms; CV: 7.4% ± 0.9% and 4.5% ± 0.6%) was comparable with MOLLI (SD: 99 ± 25 and 46 ± 12 ms; CV: 8.8% ± 2.5% and 3.9% ± 1.1%) and superior to SASHA (SD: 222 ± 89 and 132 ± 33 ms; CV: 13.8% ± 5.5% and 8.1% ± 2.0%). It was concluded that the proposed free‐breathing SAVA sequence enables more efficient 3D whole‐heart T1 estimation with good accuracy and precision.