Investigation of intravoxel incoherent motion tensor imaging for the characterization of the in vivo human heart

Purpose To investigate intravoxel incoherent motion (IVIM) tensor imaging of the in vivo human heart and elucidate whether the estimation of IVIM tensors is affected by the complexity of pseudo-diffusion components in myocardium. Methods The cardiac IVIM data of 10 healthy subjects were acquired using a diffusion weighted spin-echo echo-planar imaging sequence along 6 gradient directions with 10 b values (0 similar to 400 s/mm(2)). The IVIM data of left ventricle myocardium were fitted to the IVIM tensor model. The complexity of myocardial pseudo-diffusion components was reduced through exclusion of lowbvalues (0 and 5 s/mm(2)) from the IVIM curve-fitting analysis. The fractional anisotropy, mean fraction/mean diffusivity, and Westin measurements of pseudo-diffusion tensors (f(p) and D*) and self-diffusion tensor (D), as well as the angle between the main eigenvector of f(p)(or D*) and that of D, were computed and compared before and after excluding low b values. Results The fractional anisotropy values of f(p) and D* without lowbvalue participation were significantly higher (P< .001) than those with lowbvalue participation, but an opposite trend was found for the mean fraction/diffusivity values. Besides, after removing lowbvalues, the angle between the main eigenvector of f(p)(or D*) and that of D became small, and both f(p) and D* tensors presented significant decrease of spherical components and significant increase of linear components. Conclusion The presence of multiple pseudo-diffusion components in myocardium indeed influences the estimation of IVIM tensors. The IVIM tensor model needs to be further improved to account for the complexity of myocardial microcirculatory network and blood flow.