Quantifying precision in cardiac diffusion tensor imaging with second‐order motion‐compensated convex optimized diffusion encoding

Purpose To quantify the precision of in vivo cardiac DTI (cDTI) acquired with a spin echo, first‐ and second‐order motion‐compensated (M 1 M 2 ), convex optimized diffusion encoding (CODE) sequence. Methods Free‐breathing CODE‐M 1 M 2 cDTI were acquired in healthy volunteers (N = 10) at midsystole and diastole with 10 repeated acquisitions per phase. 95% confidence intervals of uncertainty in reconstructed diffusion tensor eigenvectors (E → 1 ,E → 2 ,E → 3 ), mean diffusivity (MD), fractional anisotropy (FA), and tensor Mode were measured using a bootstrapping approach. Trends in observed tensor metric uncertainty were evaluated as a function of scan duration, image SNR, cardiac phase, and bulk motion artifacts. Results For midsystolic scans including 5 signal averages (scan time: ∼5 min), the median myocardial 95% confidence intervals of uncertainties were:E → 1 : 15.5 ± 1.2°,E → 2 : 31.2 ± 3.5°,E → 3 : 21.8 ± 3.1°, MD: 0.38 ± 0.02 × 10 −3 mm 2 /s, FA: 0.20 ± 0.01, and Mode: 1.10 ± 0.08. Uncertainty in all parameters increased for diastolic scans:E → 1 : 31.9 ± 7.1°,E → 2 : 59.6 ± 6.8°,E → 3  : 40.5 ± 6.4°, MD: 0.52 ± 0.09 × 10 −3 mm 2 /s, FA: 0.23 ± 0.01, and Mode: 1.57 ± 0.11. Diastolic cDTI also reported higher MD (MD DIA  = 1.91 ± 0.34 × 10 −3 mm 2 /s vs. MD SYS  = 1.58 ± 0.09 × 10 −3 mm 2 /s, P  = 8 × 10 −3 ) and lower FA values (FA DIA  = 0.32 ± 0.06 vs. FA SYS  = 0.37 ± 0.03, P  = 0.03) . Conclusion cDTI precision improved with increasing nondiffusion‐weighted ( b  = 0) image SNR, but gains were minimal for SNR ≥ 25 (∼10 averages). cDTI precision was also sensitive to intershot bulk motion artifacts, which led to better precision for midsystolic imaging.