Full 3D anisotropic estimation of tissue in ultrasound imaging

In cardiac diseases or after myocardial infarction, the fibrous layout in the heart can be modified. To determine the local fiber orientation and to characterize the lesion, an imaging method is required. The fiber orientation can be determined by diffusion MRI, but various factors limit its use in a beating heart. It has been demonstrated that ultrafast ultrasound imaging can measure the local fiber orientation of an in vivo heart based on the ultrasound spatial coherence. This method only returns the fiber orientations in planes parallel to the probe surface. We propose a method called 3D coherence function to improve this initial strategy to extract the full 3D local anisotropy. To validate this approach, 3D ultrasound datasets were acquired on a phantom constituted of several wire layers mimicking different fiber layers. The acquisitions were conducted with different angles between the probe surface and the wire layers. For each dataset, the conventional approach and our 3D coherence function were computed to compare the improvement in the fiber angle evaluation. We have demonstrated that when the out-of-plane angle increases, the 3D coherence function allows a better extraction of the angle.