Aleksandra Popovic

Robust feature tracking on the beating heart for a robotic-guided endoscope

Visualization during minimally invasive bypass surgery on the beating heart can be enhanced by using a robotic‐guided endoscope and visual servoing from the endoscopic images. In order to achieve these objectives, this work has focused on developing and testing algorithms for accurate, robust and real‐time motion tracking of features on the beating heart, using marker‐less approaches and an uncalibrated endoscope.

Tracking and characterization of fragments in a beating heart using 3d ultrasound for interventional guidance

Fragments generated by explosions and similar incidents can become trapped in a patients heart chambers, potentially causing disruption of cardiac function. The conventional approach to removing such foreign bodies is through open heart surgery, which comes with high perioperative risk and long recovery times. We thus advocate a minimally invasive surgical approach through the use of 3D transesophageal echocardiography (TEE) and a flexible robotic end effector. In a phantom study, we use 3D TEE to track a foreign body in a beating heart, and propose a modified normalized cross-correlation method for improved accuracy and robustness of the tracking, with mean RMS errors of 2.3 mm. Motion analysis of the foreign body trajectory indicates very high speeds and accelerations, which render unfeasible a robotic retrieval method based on following the tracked trajectory. Instead, a probability map of the locus of the foreign body shows that the fragment tends to occupy only a small sub-volume of the ventricle, suggesting a retrieval strategy based on moving the robot end effector to the position with the highest spatial probability in order to maximize the possibility of capture.

Guidance of a high dexterity robot under 3D ultrasound for minimally invasive retrieval of foreign bodies from a beating heart

Particles such as thrombi, bullet fragments, and shrapnel can become trapped in a persons heart after migrating through the venous system, or by direct penetration. These cardiac foreign bodies pose a serious health risk as they can interfere with cardiovascular function. Conventional treatment often requires open heart surgery, cardiopulmonary bypass, and a long incision of the heart muscle, which come with significant risk and recovery time. To circumvent these disadvantages, we propose a minimally invasive surgical approach using 3D ultrasound to guide a dexterous robotic capture device. Analysis of the foreign body trajectory indicates highly erratic motion, rendering a robotic retrieval strategy based on direct pursuit of the tracked target infeasible. To provide a relatively slow robot with the ability to retrieve such a target, we propose alternative strategies based on guiding a robot to a salient capture location, and ambushing the target upon its reappearance. In this paper, we demonstrate the use of 3D transesophageal echocardiography (TEE) in tracking a foreign body in a beating heart phantom, computing a suitable capture location, and guiding a high dexterity robot to secure the target.

Multiple capture locations for 3D ultrasound-guided robotic retrieval of moving bodies from a beating heart

Free moving bodies in the heart pose a serious health risk as they may be released in the arteries causing blood flow disruption. These bodies may be the result of various medical conditions and trauma. The conventional approach to removing these objects involves open surgery with sternotomy, the use of cardiopulmonary bypass, and a wide resection of the heart muscle. We advocate a minimally invasive surgical approach using a flexible robotic end effector guided by 3D transesophageal echocardiography. In a phantom study, we track a moving body in a beating heart using a modified normalized cross-correlation method, with mean RMS errors of 2.3 mm. We previously found the foreign body motion to be fast and abrupt, rendering infeasible a retrieval method based on direct tracking. We proposed a strategy based on guiding a robot to the most spatially probable location of the fragment and securing it upon its reentry to said location. To improve efficacy in the context of a robotic retrieval system, we extend this approach by exploring multiple candidate capture locations. Salient locations are identified based on spatial probability, dwell time, and visit frequency; secondary locations are also examined. Aggregate results indicate that the location of highest spatial probability (50% occupancy) is distinct from the longest-dwelled location (0.84 seconds). Such metrics are vital in informing the design of a retrieval system and capture strategies, and they can be computed intraoperatively to select the best capture location based on constraints such as workspace, time, and device manipulability. Given the complex nature of fragment motion, the ability to analyze multiple capture locations is a desirable capability in an interventional system.