Boiko K.K.

National Technical University of Ukraine “Kiev Polytechnic Institute”

Comparison of MRI Tagging and Speckle Tracking Echocardiography Technologies for Assessment of Mechanical Cardiac Function

Mechanical cardiac function is a major determinant of the cardiac health. Deviations in the mechanical function and dyssynchronies indicate heart problems and its failure depending on the magnitude of such deflections. There are many parameters that may assess normal functionality of mechanical cardiac function: ejection fraction, stroke volume, ventricular function and variety of indexes. Assessment of these parameters and calculation of indexes requires precise cardiac imaging, and the most advanced nowadays methods used in clinical practice are MRI tagging and Speckle tracking.

Tagged MRI provides a potentially powerful new way to non-invasively assess the regional function of the heart. Although its potential has not yet been fully realized, due to remaining technical limitations in image acquisition and analysis, good progress is being made to overcome these limitations. Current research focuses on improving imaging methods to obtain high resolution 3D spatially registered tagged images, designing more efficient methods to extract the heart wall contours and tag positions within the wall from the tagged images, and implementing efficient ways to reconstruct the 3D motion of the heart from this data. In addition to the new regional motion and deformation data that tagged MRI can provide on normal and abnormal cardiac function, we can potentially use this motion data to model the corresponding forces within the heart wall [1]. Magnetic resonance imaging (MRI) of the heart with magnetization tagging provides a potentially useful new way to assess cardiac mechanical function, through revealing the local motion of otherwise indistinguishable portions of the heart wall. While still an evolving area, tagged cardiac MRI is already able to provide novel quantitative information on cardiac function. Exploiting this potential requires developing tailored methods for both imaging and image analysis [2].

Speckle-tracking echocardiography has recently emerged as a quantitative ultrasound technique for accurately evaluating myocardial function by analyzing the motion of speckles identified on routine 2-dimensional sonograms. It provides non-Doppler, angle-independent, and objective quantification of myocardial deformation and left ventricular systolic and diastolic dynamics. By tracking the displacement of the speckles during the cardiac cycle, strain and the strain rate can be rapidly measured offline after adequate image acquisition. Data regarding the feasibility, accuracy, and clinical applications of speckle-tracking echocardiography are rapidly accumulating [3].

MRI tagging is an expensive procedure that requires a specialized equipment and presence on advanced software tools. This heart examination takes several hours while Speckle tracking is a cheaper and faster technology that is considered to be less accurate. However, recent studies [4] prove its efficiency in clinic.

Both technologies are widely used for assessment of left ventricular function. And recent study revealed that although 3DSTE-derived LV volumes are underestimated in most patients compared with MRI, measurement of the LVEF revealed excellent accuracy. Measurements of CS were systematically greater with 3DSTE than with MRI, which likely reflects various inter-technique differences that preclude direct comparability of their measurements. With the understanding of these intertechnique differences, further studies should establish normal reference values of 3DSTE-derived strain measurements in a larger healthy population and determine their added usefulness over current clinical standards of LV function assessment in different clinical scenarios [4].

Another study also provides rationale for using Speckle tracking technology for accurate cardiac function assessment as an alternative to MRI tagging. Amundsen states that speckle tracking echocardiography provides accurate and angle-independent measurements of LV dimensions and strains and has potential to become a clinical bedside tool for quantifying myocardial strain [5].

In conclusion, we should admit that MRI tagging and Speckle tracking methods can be effectively used in clinic, and despite significantly less cost of STE, this method can be used as an accurate measurement of mechanical cardiac function.

References

1. Axel L. Tagged MRI-Based Studies of Cardiac Function, In Functional Imaging and Modeling of the Heart, Lecture Notes in Computer Science. Volume 2674, 2003, pp 1-7

2. Axel L., Montillo A., Kim D. Tagged magnetic resonance imaging of the heart: a survey, In Med Image Anal. 2005 Aug;9(4):376-93

3. Mondillo S., et al. Speckle-tracking echocardiography: a new technique for assessing myocardial function, In J Ultrasound Med. 2011 Jan;30(1):71-83.

4. Kleijn S., et al. Comparison between three-dimensional speckle-tracking echocardiography and cardiac magnetic resonance imaging for quantification of left ventricular volumes and function, In European Heart Journal - Cardiovascular Imaging. 2012 Feb

5. Amundsen B., et al. Noninvasive Myocardial Strain Measurement by Speckle Tracking Echocardiography: Validation Against Sonomicrometry and Tagged Magnetic Resonance Imaging, In Journal of the American College of Cardiology. Volume 47, Issue 4, 21 2006 Feb, pp 789–793