Microstructurally Anchored Cardiac Kinematics by Combining In Vivo DENSE MRI and cDTI

Abstract

Metrics of regional myocardial function can detect the onset of cardiovascular disease, evaluate the response to therapy, and provide mechanistic insight into cardiac dysfunction. Knowledge of local myocardial microstructure is necessary to distinguish between isotropic and anisotropic contributions of local deformation and to quantify myofiber kinematics, a microstructurally anchored measure of cardiac function. Using a computational model we combine in vivo cardiac displacement and diffusion tensor data to evaluate pointwise the deformation gradient tensor and isotropic and anisotropic deformation invariants. In discussing the imaging methods and the model construction, we identify potential improvements to increase measurement accuracy. We conclude by demonstrating the applicability of our method to compute myofiber strain in five healthy volunteers.

Keywords: Cardiac deformation invariants; Cardiac kinematics; Diffusion tensor imaging; Myofiber strain.

Fig. 1

(A) LV short-axis single-slice (B) including myofiber preferential orientations (principal eigenvectors) from cDTI and (C) Lagrangian displacement vectors from beginning to end systole. (D) Interpolated myofiber preferential orientations at FE quadrature points after cDTI-DENSE registration and (E) FE-based mesh deformation through systole driven by the DENSE measured displacement field.

Fig. 2

Isotropic (I₁) and anisotropic (I₄) deformation invariants: analytic invariants (A and C) and pointwise % error between analytical and numerical values (B, D) computed in Test 2.

Fig. 3

Pointwise comparison and Bland-Altman plot for I₁ (A, B) and I₄ (C, D) computed analytically and using the single slice model with DENSE simulated data (Test 3). The biases in the Bland-Altman plots are 0.125 for I₁ (B) and −0.020 for I₄ (D).

Fig. 4

(A) Displacement vectors from beginning to end systole in a healthy volunteer. (B) cDTI myofiber vectors f acquired at mid-systole. (C, D) Peak systolic deformation invariants I₁ and I₄.

Fig. 5

Time evolution of averaged I₁ (isotropic) and I₄ (anisotropic) deformation invariants in healthy volunteers (N = 5) together with intersubject mean (red line) and standard deviation (blue shaded region).