A 2D ultrasound enhanced virtual reality surgical guidance system has been developed in our laboratory. The system was tested in both the laboratory and the clinic. Recently, we studied the accuracy of two the ultrasound calibration methods with five different ultrasound transducers using a spherical object as the test platform. In this paper, we extend that work to use the superior vena cava and right atrium of a beating heart phantom as the metrological test artefact. The right atrium was imaged using the tracked ultrasound and the expected cross-sectional outline was determined using the intersection of the ultrasound plane and the surface model in the surgical guidance system. The expected and observed outlines are compared. The results show that the ultrasound calibration methods were sufficiently accurate in the spatial domain, but that temporal calibration is required to ensure accuracy throughout a given procedure.

OBJECTIVE:: Optimal atrial septal defect (ASD) closure should combine off-pump techniques with the effectiveness and versatility of open-heart techniques. We report our experience with off-pump ASD closure using the Universal Cardiac Introducer (UCI) in a porcine model. The goal was to create an ASD over the fossa ovale (FO) and position a patch over the ASD under ultrasound (US) imaging and augmented virtual reality guidance.METHODS:: An US probe (tracked with a magnetic tracking system) was positioned into the esophagus (transesophageal echocardiographic probe) for real-time image-guidance. The right atrium (RA) of six pigs was exposed via a right lateral thoracotomy or medial sternotomy. The UCI was attached to the RA wall. A punching tool was introduced via the UCI, navigated and positioned, under US guidance, to create an ASD into the FO. A patch with its holder and a stapling device were introduced into the RA via the UCI. The patch was positioned on the ASD. Occlusion of the ASD was determined using US and Doppler imaging.RESULTS:: The FO membrane was excised successfully in all animals. US image-guidance provided excellent visualization. The patch was positioned in all cases with complete occlusion of the ASD. The stapling device proved too bulky, impeding circumferential positioning.CONCLUSIONS:: Using the UCI, ASD closure was safe and feasible. US imaging, combined with virtual and augmented reality provided accurate navigating and positioning. This study also provided valuable information on the future design of anchoring devices for intracardiac procedures.