Three-dimensional tissue strain measurement using a row-column array during biaxial testing of excised ventricular myocardium

ObjectiveTo implement and validate a 3D volume imaging sequence and 3D strain estimation procedure for enhanced biaxial mechanical testing of excised ventricular myocardium. MethodsOne right- and one left-ventricular excised porcine myocardium specimens were tested using dual-loading protocol quasi-static biaxial mechanical testing. During biaxial testing, volume ultrasound images were acquired using a row-column addressed array probe using a synthetic aperture imaging sequence. Volume ultrasound images were used to compute tissue deformation using 3D correlation-based ultrasound speckle tracking. Ultrasound-derived tissue strains were validated against repeated measurements using typical standard optical camera imaging of the surface deformation of the specimen. ResultsSynthetic aperture imaging with the RCA yielded artifact-free and uniform ultrasound speckle for high-fidely speckle tracking of tissue deformation. Ultrasound-derived tissue strain is in good agreement with ground-truth camera-derived surface strain measurements (root-mean-square error is 1.6% strain). ConclusionHigh-fidelity 3D strain measurement with ultrasound 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.