Transthoracic Cardiac Strain Imaging with Electromagnetic Six Degrees-of-Freedom Tracking for 3D Coregistration

An electromagnetic tracking system was used to track the position and orientation of an ultrasound imaging probe for the coregistration of multiple 2D left-ventricular strain images, which were computed via myocardial elastography. High frame-rate radiofrequency data were acquired from a healthy human volunteer in standard short-axis and apical views, and cross-correlation searches in the axial and lateral dimensions estimated the displacement and strain of the myocardial wall throughout ventricular systole. Positional coordinates and quarterions outputted by the electromagnetic sensor were then used to automatically translate and rotate each strain image for coregistration and simultaneous visualization of all acquisitions in a 3D grid. The final result is a patient-specific, anatomically accurate representation of systolic myocardial strain throughout the left ventricle.