Abstract 10424: Prospective Motion Correction for Intra-cardiac MRI Using a Tetrahedron-shaped Array of MR-tracking Coils
Introduction: We previously showed that Intra-cardiac MRI (ICMRI) probes, providing superior signal-to-noise, can guide electrophysiology radiofrequency ablations. However, since both the heart and the coil move, blurring and image distortions may occur. We hypothesized that these motion artifacts can be corrected with prospective motion correction using MR-tracking coils on an ICMRI catheter.
Methods: A nylon mesh, carrying an imaging coil and 4 tracking coils, was mounted on a 9 fr sheath (Fig.1a). When the mesh is expanded (Fig1b), the 4 tracking coils (circles) achieve a Tetrahedron shape and the imaging coil reaches 3 cm diameter, suitable for pulmonary vein imaging. By capturing the 3D position of each tracking coil, six-degrees-of-freedom motion could be delineated at 30Hz. A segmented gradient-echo sequence was modified to allow for prospective correction of each imaging segment, using the tracking data, so that the entire image was acquired in a static frame of reference. Four ex-vivo swine hearts were imaged during 10mm translational (in-plane and through-plane) and 5° rotational motion, simulating respiratory and cardiac motion. A surface coil moving with the device was also used in these experiments.
Results: Compare 0.6*0.6mm2 images taken (1c) without motion, (1d) with translational+rotational motion, but without correction, and (1e) with motion and with correction. Motion correction restored moving image quality (IQ) to approximately the non-moving IQ; the 1D correlation along the red line between moving+corrected and static is 0.97, vs. only 0.87 between moving+uncorrected and static. The largest improvement was observed during through-plane motion.
Conclusion: Prospective motion correction using Tetrahedron-shaped tracking coils effectively removes motion artifacts from high-resolution MR imaging performed during large-amplitude intra-cardiac motion, while the expandable array allows for vascular deployment into the heart.
- © 2010 by American Heart Association, Inc.