A new method for two-dimensional myocardial strain estimation by ultrasound: an in-vivo comparison with sonomicrometry

At present, ultrasonic strain and strain rate imaging only give information on the deformation occurring along the image line. As a result, the techniques have been shown to be angle dependent. As a first step to overcome this problem, fully resolved two-dimensional (2D) strain estimates are required. We have developed a new methodology for the estimation of 2D strain based on in-silico and in-vitro experiments. The paper reports a study which further develops and validates this methodology in an in-vivo setting. Ultrasound RF data were acquired in a parasternal long axis view. Myocardial radial and longitudinal strain components were simultaneously estimated in the inferolateral wall using the new methodology from single RF data sets. After baseline acquisitions, the deformation was altered. Ultrasonically estimated peak systolic radial and longitudinal strain were validated against sonomicrometry by means of linear regression and Bland-Altman analysis. For both strain components, good agreement was found between the ultrasound and the sonomicrometry measurements. Simultaneous estimation of both in-plane myocardial strain components using our methodology gave accurate information on myocardial deformation in the in-vivo setting. Myocardial strain can thus be assessed in-plane, independent of insonation angle. This could potentially accelerate the clinical acceptance of deformation imaging in cardiology.