Three-Dimensional Tissue Strain Measurement Using a Row–Column Array During Biaxial Testing of Excised Ventricular Porcine Myocardium

This technical note introduces and validates a three-dimensional (3D) strain measurement technique that combines volumetric ultrasound imaging with biaxial mechanical testing to assess the anisotropic mechanical response of porcine ventricular myocardium. Samples from right and left ventricles were stretched biaxially using a dual-loading protocol on a BioTester 5000 while imaged with a row–column addressed ultrasound array. Synthetic aperture beamforming reconstructed full 3D volumes, allowing correlation-based 3D speckle tracking to estimate deformation throughout the entire tissue thickness. Ultrasound-derived 3D strains closely matched optical camera–derived surface strains (RMSE 1.6%), confirming volumetric accuracy. This method provides improved insight into myocardial mechanics under realistic 3D deformation states beyond the plane-stress assumption.