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

Objective: To implement and validate a 3D volume imaging sequence and 3D strain estimation procedure for enhanced biaxial mechanical testing of excised ventricular myocardium.

Methods: One specimen of right and one of left ventricular excised porcine myocardium were tested using dual-loading protocol quasistatic biaxial mechanical testing. During biaxial testing, volume ultrasound (US) images were acquired using a row-column addressed array probe using a synthetic aperture imaging sequence. Volume US images were used to compute tissue deformation using 3D correlation-based US speckle tracking. US-derived tissue strains were validated against repeated measurements using conventional optical camera imaging of the specimen surface deformation.

Results: Speckle tracking yielded high-fidelity maps of tissue deformation in 3D throughout the entire sample volume. US-derived tissue strain is in good agreement with ground-truth camera-derived surface strain measurements (root mean square error is 1.6% strain).

Conclusion: The 3D full-thickness strain measurement with US imaging is accurate and can enhance biomechanical insights from biaxial experimentation, especially in large tissues such as porcine and human myocardium where assumptions of plane stress and incompressibility may not apply.