Abstract
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 (E⃗(1), E⃗(2), E⃗(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: ~5min), the median myocardial 95% confidence intervals of uncertainties were: E⃗(1): 15.5 ± 1.2°, E⃗(2): 31.2 ± 3.5°, E⃗(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: E⃗(1): 31.9 ± 7.1°, E⃗(2): 59.6 ± 6.8°, E⃗(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.