Free-breathing myocardial T1 mapping using magnetization-prepared slice interleaved spoiled gradient echo imaging
Journal of Cardiovascular Magnetic Resonance volume 17, Article number: W7 (2015)
Quantitative myocardial T1 mapping and extracellular volume fraction (ECV) show promise for non-invasive assessment of cardiomyopathies. Most available T1 mapping sequences use a single slice breath-hold acquisition with balanced steady state free precession (b-SSFP) readout . However, b-SSFP readout is sensitive to B0 field inhomogeneity and is potentially T2 dependent . In this study, we sought to investigate the feasibility of a free breathing multi-slice T1 mapping sequence using slice-interleaved spoiled gradient echo (GRE) imaging.
The proposed sequence used multiple inversion recovery (IR) experiments. In each IR experiment, a non-selective inversion pulse is applied and followed by the acquisition of 5 slices over the next 5 heart beats, and 3 rest cycles . This IR experiment is repeated 5 times using different slice orders to obtain signal samples at TI, TI + 1 RR, TI + 2 RR, TI + 3 RR, TI + 4 RR. This block of 5 IR experiments is finally repeated using a different TI value. The fully recovered longitudinal magnetization is also initially acquired for each slice without any IR pulse (∞ image). Respiratory motion was corrected using prospective slice tracking and retrospective image registration. ECG-triggered single shot acquisitions were used with GRE readout (TR/TE/α=4.3/2.1ms/10˚, FOV=280×272 mm2, voxel size=2×2 mm2, slice thickness=8 mm, 5 slices, 43 phase-encoding lines, linear ordering, 10 linear ramp-up pulses, SENSE factor=2.5, half Fourier=0.75, bandwidth=382Hz/pixel). For comparison, MOLLI  was acquired with a b-SSFP readout and similar parameters (except TR/TE/α=2.6/1.3ms/70°, 1 slice, bandwidth=1785 Hz/pixel). Imaging was performed on a 1.5 T Philips scanner. T1 accuracy, precision, and reproducibility were evaluated in simulations and phantom. In-vivo spatial variability and reproducibility of native T1 mapping was measured in 11 healthy adult subjects (35±21y, 4 m), imaged 5 times with each sequence. Three of these subjects were also imaged at ~15min after contrast injection to demonstrate the feasibility of ECV mapping.
The proposed sequence provided improved accuracy and similar precision than MOLLI in both simulation and phantom experiments (accuracy: p=0.01; precision: p=0.16). MOLLI was more reproducible in phantom (p<0.001). In-vivo, the proposed sequence yielded higher native T1 times than MOLLI (1094±24ms vs. 1010±27ms, p<0.001) with similar spatial variability (58±7ms vs. 61±9ms, p=0.44) and reproducibility (25±9ms vs. 17±8ms, p=0.15). ECV measurements were 0.21±0.01 using the proposed sequence.
Free breathing multi-slice T1 mapping using a magnetization-prepared slice interleaved spoiled GRE imaging is feasible and yields similar in-vivo precision/reproducibility as MOLLI but with improved accuracy. In addition, the proposed sequence allows simultaneous imaging of 5 slices within free-breathing in 100 sec.
Kelmann : JCMR. 2014
Weingärtner : MRM. 2014
Messroghli : MRM. 2004
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Roujol, S., Jang, J., Basha, T.A. et al. Free-breathing myocardial T1 mapping using magnetization-prepared slice interleaved spoiled gradient echo imaging. J Cardiovasc Magn Reson 17 (Suppl 1), W7 (2015). https://doi.org/10.1186/1532-429X-17-S1-W7