Regional Strain and Strain Rate Measurements by Cardiac Ultrasound: Principles, Implementation and Limitations

Abstract

The non-invasive quantification of regional myocardial function is an important goal in clinical cardiology. Myocardial thickening/thinning indices is one method of attempting to define regional myocardial function. A new ultrasonic method of quantifying regional deformation has been introduced based on the principles of 'strain' and 'strain rate' imaging. These new imaging modes introduce concepts derived from mechanical engineering which most echocardiographers are not familiar with. In order to maximally exploit these new techniques, an understanding of what they measure is indispensable. This paper will define each of these modalities in terms of physical principles and will give an introduction to the principles of data acquisition and processing required to implement ultrasonic strain and strain rate imaging. In addition, the current status of development of the technique and its limitations will be discussed, together with examples of potential clinical applications.

Medical ultrasound: imaging of soft tissue strain and elasticity

“…Regional ultrasonic myocardial strain and strain rate measurements have been in clinical use for more than 10 years [193]. During this time, the technique has evolved from being based on simple continuous one-dimensional measurements of the thickness of the myocardium over the cardiac cycle, through two-dimensional [194] to three-dimensional [195] approaches, providing increasingly complete pictures of cardiac function.…”

The development of, and future for, fetal functional cardiac imaging techniques

“…Speckle tracking involves tracking bright points of myocardium that are generated by natural acoustic reflections. When these individual points are followed, it is possible to evaluate the overall deformation of the myocardium, and when a time integral is introduced this generates velocity vectors, that can be used to calculate displacement, velocity, deformation (strain) and velocity of deformation (strain rate) in the cardiac wall 9 . Readers are directed to a number of extensive reviews of techniques for evaluating fetal cardiac function, 2 , 10 one of which was contained within a focussed fetal cardiac function edition of the journal Fetal Diagnosis and Therapy from 2012 that can be accessed at the following location: http://www.karger.com/Book/Home/257215.…”

Assessment of the Left Ventricle Wall Motion Using Tagged Magnetic Resonance Imaging Data (tMRI)

“…This is nothing but Lagrangian strain with the (fixed) end-diastolic wall thickness. The rate at which the myocardial wall contract and expand is the one dimension SR [8]. The Heart coordinate system: Figure 2(a), shows the local heart coordinate system which be defined as follows: For each point to be interrogated in any myocardial wall, three mutually perpendicular axes can be defined: The radial (R), The longitudinal (Lo) and The circumferential (C) axis.…”