Towards CT Enhanced Ultrasound Guidance for Off-pump Beating Heart Mitral Valve Repair

Off-pump beating heart interventions require a good guidance system to show both cardiac anatomy and motion. Over the years, echocardiography has become a popular solution for such a purpose because of its real-time imaging capability, flexibility, non-invasiveness, and low cost. However, it can be difficult for surgeons to appreciate the position and orientation of 2D images and to keep surgical tools and targets both shown in the image plane with only ultrasound guidance. In this paper, we propose to use CT images as high-quality 3D context to enhance ultrasound images through image registration to provide a better guidance system with very few changes to standard workflow. We have also developed a method to generate synthetic 4D CT images through non-rigid registration, when dynamic pre-operative CT images are not available. The validation of synthetic CT images was performed by comparing them to real dynamic CT images and the validation of CT-ultrasound registration was performed with static, dynamic, and synthetic CT images.