Surgical Simulation and Surgical Guidance

During 2008 a new emphasis was placed on registration applications in model-based surgical guidance, in addition to the continuance of research in surgery simulation.

 
Patient-specific High-Resolution Ear Model for Surgical Guidance

Image guidance of ear surgery would enable an ENT surgeon to navigate about the components of the middle and inner ear, but the elaboration of anatomical models for this application is limited by the resolution of CT and its inability to distinguish among soft tissues.We proposed a method for producing a patient-specific description of the middle and inner ear on the basis of the minimally supervised registration of a high resolution model elaborated from microMR to patient CT, where the transformation between the model and the patient data is determined in a component-wise coarse-to-fine strategy.
Figure 11 shows the results of the registration process: the micorMR model is overlaid on the CT at the correct position allowing for accurate navigation of the middle and inner ear.

3D-2D Registration of Cardiac Images for Transapical Aortic Stent Replacement

In aortic stent placement there is a safe zone where the stent must be placed to avoid adverse effects to the patient. Finding this area is not easy for the surgeon, using intraoperative fluoroscopic images, and requires help from a cardiologist. On-going work focused on determining the projective pose of the fluoroscopic image in relation to preoperative CT. Digital reconstructed radiographs (DRR) for registering CT to fluoroscopic images are first computed. The DRRs and fluoroscopic images are then registered with the mutual information (MI) and gradient difference (GD) metrics.

Currently, we find the out-of-plane transformation for the DRR by hand-registering it. We then finally find the in-plane registration by using MI or GD together with a multiresolution approach. Figure 2 shows the overlaid DRR and fluoroscopy images after the registration process. The vertebras align up well indicating that the registration was successful.