In this paper, we present a filtering method for estimating the shape and end effector pose of a highly articulated surgical snake robot. Our algorithm introduces new kinematic models that are used in the prediction step of an extended Kalman filter whose update step incorporates measurements from a 5-DOF electromagnetic tracking sensor situated at the distal end of the robot. A single tracking sensor is sufficient for estimating the shape of the system because the robot is inherently a follow-the-leader mechanism with well defined motion characteristics. We therefore show that, with appropriate steering motion, the state of the filter is fully observable. The goal of our shape estimation algorithm is to create a more accurate and representative 3D rendered visualization for image-guided surgery. We demonstrate the feasibility of our method with results from an animal experiment in which our shape and pose estimate was used as feedback in a control scheme that semi-autonomously drove the robot along the epicardial surface of a porcine heart.

Heart failure resulting from myocardial infarct, oxygen-deprived tissue death, is a serious disease that affects over 20 million patients in the world. The precise injection of tissue-engineered materials into the infarct site is emerging as a treatment strategy to improve cardiac function for patients with heart failure. We have developed a novel miniature robotic device (HeartLander) that can act as a manipulator for precise and stable interaction with the epicardial surface of the beating heart by mounting directly to the organ. The robot can be delivered to and operate within the intrapericardial space with the chest closed, through a single small incision below the sternum. The tethered crawling device uses vacuum pressure to maintain prehension of the epicardium, and a drive wire transmission motors for actuation. An onboard electromagnetic tracking sensor enables the display of the robot location on the heart surface to the surgeon, and closed-loop control of the robot positioning to targets. In a closed-chest animal study with the pericardium intact, HeartLander demonstrated the ability to acquire a pattern of targets located on the posterior surface of the beating heart within an average of 1.7 ± 1.0 mm. Dye injections were performed following the target acquisitions to simulate injection therapy for heart failure. HeartLander may prove useful in the delivery of intrapericardial treatments, like myocardial injection therapy, in a precise and stable manner, which could be performed on an outpatient basis.

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