The rapid adoption of aggressive treatments for heart failure, including resynchronization pacing, has renewed interest in the fundamental electromechanical properties of the left ventricle. Related to MRI, this has resulted in research efforts aimed at the development and application of methods to assess left ventricular mechanics, including magnetic resonance tissue tagging, phase velocity myocardial mapping and cine DENSE displacement mapping in 3D space. By comparison, there have been fewer efforts to study right ventricular mechanics, even though in certain conditions such as congenital heart diseases, pulmonary hypertension and cor pulmonale, RV function can be more important than LV function. In echocardiography, the development of tissue Doppler strain rate methods have been by now followed by newer speckle tracking methods capable of showing multiple types of strain deformation without angle dependency, including circumferential shortening strain, radial thickening strain in systole and twisting and untwisting. Two-dimensional methods can define, to some extent, segmental motion in cross-sectional views, but are compounded by through-plane motion. For both echo and MRI, it will likely require a robust 3D method to comprehensively define regional ventricular wall motion and deformation. This proposal is aimed at development and validation of a method to obtain spatially-dense displacement fields of both left and right ventricular deformation maps from ultrasound scans performed on an advanced 3D echocardiographic system;a method that should be capable of showing strain displacement fields and torsional deformation for both ventricles. This proposal is aimed at further developing the techniques we have pioneered and validating them in a unique dynamic cardiac phantom and in open-chest pigs using sonomicrometry as a gold standard. We will also evaluate the efficacy of our new approach and translate it to the clinical setting by studying patients with congenital heart disease and compare our results from our method MRI tagging, and wall velocity encoded strain measurements.
Much interest exists in Cardiology in the recently developed 4D ultrasound technologies for imaging the heart. We believe that as informative as these dynamic qualitative anatomical diagnostic images are, the quantitative aspects of these 4D methods for defining cardiac mechanics are likely more important. The spatially-dense 4D speckle tracking method which we have developed and hope to further refine and test in this proposal could provide a method for study of the dynamic biventricular function of the heart, which could, in turn, improve therapeutic approaches to treatment of heart disease.
|Zhang, Zhijun; Ashraf, Muhammad; Sahn, David J et al. (2014) Temporally diffeomorphic cardiac motion estimation from three-dimensional echocardiography by minimization of intensity consistency error. Med Phys 41:052902|
|Ashraf, Muhammad; Zhou, Zhiwen; Nguyen, Thuan et al. (2012) Apex to base left ventricular twist mechanics computed from high frame rate two-dimensional and three-dimensional echocardiography: a comparison study. J Am Soc Echocardiogr 25:121-8|