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Model-based respiratory motion correction using 3-D echocardiography

In this paper we investigate the use of 3-D echocardiography (echo) data for respiratory motion correction of MRI-derived roadmaps in image-guided interventions. By a combination of system calibration and tracking the MRI and echo coordinate systems are aligned. 3-D echo images at different respiratory positions are registered to an end-exhale 3-D echo image using a registration algorithm that uses a similarity measure based on local orientation and phase differences. We first assess the use of the echo-echo registration alone to perform motion-correction in the MRI coordinate system. Next, we investigate combining the echo-echo similarity measure with a MRI-derived motion model. Using experiments with cardiac MRI and 3-D echo data acquired from 2 volunteers, we demonstrate that significantly faster and more robust performance can be obtained using the motion model.