Application of XMR 2D-3D registration to cardiac interventional guidance

We describe a registration and tracking technique to integrate cardiac x-ray images and cardiac magnetic resonance (MR) images acquired from a combined x-ray and MR interventional suite (XMR). Optical tracking is used to determine the transformation matrices relating MR and x-ray image coordinates. Calibration and tracking enable us to combine x-ray projection images with registered projection MR images from a volume acquisition, and to display 3D reconstructions of catheters within the MR volume. Registration errors were assessed using phantom experiments. Errors in the combined projection images (2D root mean square target registration error - RMS TRE) were found to be 2.4 - 4.2 mm, and the errors in the integrated volume representation (3D RMS TRE) were found to be 4.6 - 5.1 mm. These errors are clinically acceptable for alignment of images of the heart and the great vessels. We demonstrate that our technique can be used to guide catheters and to combine electrical and mechanical information in the context of the patient-specific anatomy for a patient undergoing cardiac radio-frequency (RF) ablation.