Intra-cardiac 2D US to 3D CT image registration

Intra-cardiac echocardiography (ICE) is commonly used to guide intra-cardiac procedures, such as the treatment of atrial fibrillation (AF). However, effective surgical navigation based on ICE images is not trivial, due to the low signal-tonoise ratio (SNR) and limited field of view of ultrasound (US) images. The interpretation of ICE can be significantly improved if correctly placed in the context of three-dimensional magnetic resonance (MR) or computed tomography (CT) images by simultaneously presenting the complementary anatomical information from the two modalities. The purpose of this research is to demonstrate the feasibility of multimodality image registration of 2D intra-cardiac US images with 3D computed tomography (CT) images. In our previous work, a two-step registration procedure has been proposed to register US images with NM images and was validated on a patient dataset. In this work, we extend the two-step method to intra-cardiac procedures and provide a detailed assessment of registration accuracy by determining the target registration errors (TRE) on a heart phantom, which had fiducial markers affixed to the surface to facilitate evaluation of registration accuracy. The resultant TRE on the heart phantom was 3.7 mm. This result is considered to be acceptable for guiding a probe in the heart during ablative therapy for atrial fibrillation. To our knowledge, there is no previous report describing multimodality registration of 2D intra-cardiac US to high-resolution 3D CT.