Impact of motion correction on reproducibility and spatial variability of quantitative myocardial T2 mapping

Background: To evaluate and quantify the impact of a novel image-based motion correction technique in myocardial T-2 mapping in terms of measurement reproducibility and spatial variability. Methods: Twelve healthy adult subjects were imaged using breath-hold (BH), free breathing (FB), and free breathing with respiratory navigator gating (FB + NAV) myocardial T-2 mapping sequences. Fifty patients referred for clinical CMR were imaged using the FB + NAV sequence. All sequences used a T-2 prepared (T(2)prep) steady-state free precession acquisition. In-plane myocardial motion was corrected using an adaptive registration of varying contrast-weighted images for improved tissue characterization (ARCTIC). DICE similarity coefficient (DSC) and myocardial boundary errors (MBE) were measured to quantify the motion estimation accuracy in healthy subjects. T-2 mapping reproducibility and spatial variability were evaluated in healthy subjects using 5 repetitions of the FB + NAV sequence with either 4 or 20 T(2)prep echo times (TE). Subjective T-2 map quality was assessed in patients by an experienced reader using a 4-point scale (1-non diagnostic, 4-excellent). Results: ARCTIC led to increased DSC in BH data (0.85 +/- 0.08 vs. 0.90 +/- 0.02, p = 0.007), FB data (0.78 +/- 0.13 vs. 0.90 +/- 0.21, p < 0.001), and FB + NAV data (0.86 +/- 0.05 vs. 0.90 +/- 0.02, p = 0.002), and reduced MBE in BH data (0.90 +/- 0.40 vs. 0.64 +/- 0.19 mm, p = 0.005), FB data (1.21 +/- 0.65 vs. 0.63 +/- 0.10 mm, p < 0.001), and FB + NAV data (0.81 +/- 0.21 vs. 0.63 +/- 0.08 mm, p < 0.001). Improved reproducibility (4TE: 5.3 +/- 2.5 ms vs. 4.0 +/- 1.5 ms, p = 0.016; 20TE: 3.9 +/- 2.3 ms vs. 2.2 +/- 0.5 ms, p = 0.002), reduced spatial variability (4TE: 12.8 +/- 3.5 ms vs. 10.3 +/- 2.5 ms, p < 0.001; 20TE: 9.7 +/- 3.5 ms vs. 7.5 +/- 1.4 ms) and improved subjective score of T-2 map quality (3.43 +/- 0.79 vs. 3.69 +/- 0.55, p < 0.001) were obtained using ARCTIC. Conclusions: The ARCTIC technique substantially reduces spatial mis-alignment among T-2-weighted images and improves the reproducibility and spatial variability of in-vivo T-2 mapping.