The quantitative assessment of cardiac strain is increasingly performed to provide valuable insights on heart function. Currently, the most frequently used technique in the clinic is ultrasound-based speckle tracking echocardiography (STE). However, verification and validation of this modality are still under investigation and further reference measurements are required to support this activity.

The aim of this work was to enable these reference measurements using a dynamic beating heart simulator to ensure reproducible, controlled, and realistic haemodynamic conditions and to validate the reliability of optical-based three-dimensional digital image correlation (3D-DIC) for a dynamic full-field analysis of epicardial strain.

Specifically, performance assessment of 3D-DIC was carried out by evaluating the accuracy and repeatability of the strain measurements across multiple cardiac cycles in a single heart and between five hearts. Moreover, the ability of this optical method to differentiate strain variations when different haemodynamic conditions were imposed in the same heart was examined.

Strain measurements were successfully accomplished in a region of the lateral left ventricle surface. Results were highly repeatable over heartbeats and across hearts (intraclass correlation coefficient = 0.99), whilst strain magnitude was significantly different between hearts, due to change in anatomy and wall thickness. Within an individual heart, strain variations between different haemodynamic scenarios were greater than the estimated error of the measurement technique.

This study demonstrated the feasibility of applying 3D-DIC in a dynamic passive heart simulator. Most importantly, non-contact measurements were obtained at a high spatial resolution ($~$ 1.5 mm) allowing resolution of local variation of strain on the epicardial surface during ventricular filling. The experimental framework developed in this paper provides detailed measurement of cardiac strains under controlled conditions, as a reference for validation of clinical cardiac strain imaging modalities.

越来越多地进行心脏应变的定量评估，以提供有关心脏功能的宝贵见解。当前，临床上最常用的技术是基于超声的斑点跟踪超声心动图（STE）。但是，这种方式的验证和确认仍在研究中，并且需要进一步的参考测量来支持此活动。

这项工作的目的是使用动态心脏跳动模拟器来进行这些参考测量，以确保可再现，受控和现实的血液动力学状况，并验证基于光学的三维数字图像相关性（3D-DIC）的可靠性。心外膜应变的全视野分析。

具体而言，通过评估单个心脏中和五个心脏之间的多个心脏周期中的应变测量结果的准确性和可重复性，来进行3D-DIC的性能评估。此外，还研究了这种光学方法在同一心脏中施加不同血液动力学条件时区分应变变化的能力。

在左心室侧面的区域成功完成了应变测量。结果在心跳和整个心脏上均具有高度可重复性（类内相关系数= 0.99），而由于解剖结构和壁厚的变化，心脏之间的应变幅度也存在显着差异。在单个心脏内，不同血液动力学情况之间的应变变化大于测量技术的估计误差。

这项研究证明了在动态被动心脏模拟器中应用3D-DIC的可行性。最重要的是，非接触式测量是在高空间分辨率下获得的（$〜$1.5 mm）可以解决心室充盈期间心外膜表面应变的局部变化。本文开发的实验框架提供了在受控条件下对心脏应变的详细测量，作为临床心脏应变成像模式验证的参考。