Towards navigation on the heart surface during coronary arterty bypass grafting

Coronary artery bypass grafting (CABG) is the standard treatment for advanced coronary artery diseases. In a preoperative MSCT, both wall plaque formations and resulting optimal anastomotic site are visible to the surgeon. During surgery, the identification of this position on the surface of the heart is of utmost importance for an effective revascularisation procedure. To assist the surgeon in this matter, a surgical navigation system for the open heart is desirable. This work focusses on an appropriate method for registration of a patient-specific map of the coronaries extracted from preoperative MSCT data with optical tracking data recorded intraoperatively at the ischaemic heart.

The proposed registration process is based on mutually shared anatomical point landmarks and vessel paths on the heart surface utilised in an enhanced weighted ICP algorithm. Bypass grafting predominantly takes place at the ischaemic heart which is significantly distorted compared to its preoperative shape. To account for that, the method includes corrections for the effects of muscle relaxation and torsion of the ischaemic heart.

The registration process was tested retrospectively on real patient data recorded at the ischaemic heart during bypass grafting. After registration, the vessel paths and point landmarks recorded intraoperatively by the surgeon showed good accordance with the preoperative map of the coronaries.

The registration method presented here is capable of matching the relevant parts of a preoperatively extracted map of the coronaries with intraoperatively recorded optical tracking data. Thus, it can be used as a basis for a surgical navigation system intended to assist the surgeon in the localisation of the optimal anastomotic site during CABG.