Motion correction for free breathing quantitative myocardial t2 mapping: impact on reproducibility and spatial variability
Journal of Cardiovascular Magnetic Resonance volume 17, Article number: W5 (2015)
Quantitative myocardial T2 mapping is a promising technique for in-vivo assessment of inflammation and edema . Free breathing T2 mapping sequences increase the flexibility in the choice of the number of T2prep echoes times (TET2P), but should be combined with respiratory motion correction technique . In this study, we sought to evaluate the performance of the Adaptive Registration of varying Contrast-weighted images for improved TIssue Characterization (ARCTIC) algorithm  for in-plane motion correction in T2 mapping data and its impact on in-vivo reproducibility and spatial variability of myocardial T2 estimates.
Seven healthy adult subjects (30±17y, 3male) were imaged using a 1.5 T Phillips scanner. T2 mapping was performed using either 1) a "T2P4TE" sequence (4 T2prep echo times=[0, 25, 50, ∞]), or 2) a "T2P20TE" sequence (20 T2prep echo times=[0, 25, 30, 35, …, 95, 100, ∞, ∞, ∞]) . TET2P=∞ was simulated by acquiring an image immediately after a saturation pulse . Each subject was imaged using eight T2 mapping scans in the following order: 1) breath-held T2P4TE (BH), 2) free breathing T2P4TE without respiratory navigator (FB), 3) free breathing T2P4TE with respiratory navigator (FB+NAV), and 4) free breathing T2P20TE with respiratory navigator (5 repetitions). The same 2D short axis slice was acquired with all scans using single-shot ECG-triggered acquisitions with balanced SSFP imaging readout (TR/TE/α=2.7ms/1.35ms/85°, FOV=240×240mm2, resolution=2.5×2.5×8mm3, 10 linear ramp-up pulses, SENSE rate=2, 51 phase encoding lines, linear ordering). Accuracy of in-plane motion correction was evaluated in the first three scans by measurements of the DICE similarity coefficients (DSC) (1: ideal registration, 0: none) and the myocardial boundary error (MBE) with and without using ARCTIC. T2 mapping reproducibility and spatial variability with and without using ARCTIC was evaluated over the entire myocardium using the 5 repetitions of the T2P20TE sequence and 1) a subset of 4 T2prep echo times=[0ms, 25ms, 50ms, ∞] (referred to as 4TE ) and 2) all 20 T2prep echo times (referred to as 20TE).
ARCTIC increased DSC in BH data (0.90±0.02 vs. 0.87±0.05, p=0.09), FB data (0.91±0.02 vs. 0.79±0.15, p=0.009), and FB+NAV data (0.90±0.02 vs. 0.86±0.08, p=0.039), and reduced MBE in BH data (0.63±0.09 vs. 0.74±0.12, p=0.049), FB data (0.60±0.12 vs. 1.16±0.71, p=0.007), and FB+NAV data (0.61±0.13 vs. 0.83±0.28, p=0.025). ARCTIC improved the reproducibility (4TE: 5.0±2.3ms vs. 5.9±3.1ms, p=0.011; 20TE: 2.4±1.0ms vs. 4.3±3.9ms, p=0.002) and reduced spatial variability (4TE: 11.1±3.6ms vs. 13.7±4.3ms, p<0.001; 20TE: 7.9±1.8ms vs. 10.6±5.3ms, p=0.001) of in-vivo T2 mapping.
The ARCTIC technique substantially reduces spatial mis-alignment among T2-weighted images and improves both the reproducibility and the spatial variability of in-vivo T2 mapping.
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Roujol : MRM. 2014
Akçakaya : MRM. 2014
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Roujol, S., Basha, T.A., Weingartner, S. et al. Motion correction for free breathing quantitative myocardial t2 mapping: impact on reproducibility and spatial variability. J Cardiovasc Magn Reson 17 (Suppl 1), W5 (2015). https://doi.org/10.1186/1532-429X-17-S1-W5