Catheter navigation support for mechanical thrombectomy guidance: 3D/2D multimodal catheter-based registration with no contrast dye fluoroscopy.

PURPOSE: The fusion of pre-operative imaging and intra-operative fluoroscopy may support physicians during mechanical thrombectomy for catheter navigation from the aortic arch to carotids. Nevertheless, the aortic arch volume is too important for intra-operative contrast dye injection leading to a lack of common anatomical structure of interest that results in a challenging 3D/2D registration. The objective of this work is to propose a registration method between pre-operative 3D image and no contrast dye intra-operative fluoroscopy. METHODS: The registration method exploits successive 2D fluoroscopic images of the catheter navigating in the aortic arch. The similarity measure is defined as the normalized cross-correlation between a binary combination of catheter images and a pseudo-DRR resulting from the 2D binary projection of the pre-operative 3D image (MRA or CTA). The 3D/2D transformation is decomposed in out-plane and in-plane transformations to reduce computational complexity. The 3D/2D transformation is then obtained by maximizing the similarity measure through multiresolution exhaustive search. RESULTS: We evaluated the registration performance through dice score and mean landmark error. We evaluated the influence of parameters setting, aortic arch type and 2D navigation sequence duration. Results on a physical phantom and data from a patient who underwent a mechanical thrombectomy showed good registration accuracy with a dice score higher than 92% and a mean landmark error lower than the quarter of a carotid diameter (8-10 mm). CONCLUSION: A new registration method compatible with no contrast dye fluoroscopy has been proposed to guide the crossing from aortic arch to a carotid in mechanical thrombectomy. First evaluation showed the feasibility and accuracy of the method as well as its compatibility with clinical routine practice.

ERCP 2.0: Biliary 3D-reconstruction in patients with malignant hilar stricture.

BACKGROUND: Endoscopic retrograde cholangiopancreatography (ERCP) for malignant hilar strictures is challenging. The correlation between Magnetic resonance cholangiopancreatography (MRCP) and per ERCP 2D fluoroscopic images is not obvious. The aim of this study was to evaluate the feasibility and potential usefulness of MRCP-based handmade biliary 3D reconstruction in this setting. METHODS: Methods Patients who underwent MRCP followed by ERCP for biliary drainage of a malignant hilar stricture at our institution between 2018 and 2020 were reviewed. A handmade 3D segmentation using 3D slicer© (Kitware, France) was fashioned and reviewed with an expert radiologist. The primary outcome was the feasibility of biliary segmentation. RESULTS: A total of 16 patients were included. The mean age was 70.1 (+/- 8.6) years-old and 68.8% had hilar cholangiocarcinoma. Handmade segmentation was successful in all cases. The agreement between the MRCP interpretation and the 3D reconstruction was 37.5%, as per the Bismuth classification. 3D reconstruction available prior to ERCP could have helped guide for better stent placement in 11 cases (68.8%). CONCLUSIONS: MRCP-based biliary 3D segmentation-reconstruction, in patients with malignant hilar stricture is feasible and seems to provide a better anatomical understanding compared to MRCP and could help improve endoscopic management.

Simulation of multi-curve active catheterization for endovascular navigation to complex targets.

The recent development of endovascular therapies has been accompanied by increasingly accurate navigation simulations to assist surgeons in decision making processes or to produce training tools. However, they have been focused mostly on targets within the aortic vasculature. In order to reach complex targets such as cerebral arteries by endovascular navigation, an active guidewire made of a Shape Memory Alloy (SMA) was recently proposed. The active part becomes deformed by the Joule effect and this deformation induces a bending of the guidewire. This setup is particularly suited for facilitating the access to Supra-Aortic Trunks (SATs) and, in our case, especially the left carotid artery. A complete characterization of the endovascular active navigation was conducted. In this framework, a test bench was developed to obtain an order of magnitude of the velocities applied on the guidewire as well as on the passive catheter going along with it in endovascular navigation. A numerical model was developed and validated in the case of navigation in a complex phantom aorta. We succeeded in representing crucial phenomena observed experimentally: snapping, active curvatures, interactions between the tools. In the last part of this study, it was demonstrated that adapting the guidewire design made it possible to hook the left carotid on three complex aortas.

Instruments Segmentation in X-ray Fluoroscopic Images for Endoscopic Retrograde Cholangio Pancreatography.

In this work, we propose a method to segment endoscope and guidewire from 2D X-ray fluoroscopic images of an endoscopic retrograde cholangiopancreatography (ERCP). We used an improved U-Net model. We obtained a Dice score of 0.94±0.05 for endoscope segmentation and a Hausdorff distance of 24.26 pixels for the guidewire segmentation. These preliminary results pave the way for further applications aiming at aiding the medical procedure.

Shared Control Schemes for Middle Ear Surgery.

This paper deals with the control of a redundant cobot arm to accomplish peg-in-hole insertion tasks in the context of middle ear surgery. It mainly focuses on the development of two shared control laws that combine local measurements provided by position or force sensors with the globally observed visual information. We first investigate the two classical and well-established control modes, i.e., a position-based end-frame tele-operation controller and a comanipulation controller. Based on these two control architectures, we then propose a combination of visual feedback and position/force-based inputs in the same control scheme. In contrast to the conventional control designs where all degrees of freedom (DoF) are equally controlled, the proposed shared controllers allow teleoperation of linear/translational DoFs while the rotational ones are simultaneously handled by a vision-based controller. Such controllers reduce the task complexity, e.g., a complex peg-in-hole task is simplified for the operator to basic translations in the space where tool orientations are automatically controlled. Various experiments are conducted, using a 7-DoF robot arm equipped with a force/torque sensor and a camera, validating the proposed controllers in the context of simulating a minimally invasive surgical procedure. The obtained results in terms of accuracy, ergonomics and rapidity are discussed in this paper.

Statistical shape model of vessel centerline for endovascular paths comparison in mechanical thrombectomy.

Endovascular interventions are experiencing an important development. Despite many advantages of this type of intervention, catheter navigation is still a cause of difficulties or failure. Mechanical thrombectomy is one of these interventions where navigation difficulties are related to the ability to navigate the aortic arch and access the carotid. These difficulties are due to the selection of adequate catheters and guides for a specific anatomy and to the technical gesture to operate. The objective of this work is to propose a method to find similar endovascular navigation paths from pre-existing patients to support intervention in mechanical thrombectomy. For each patient, iso-centerlines of the aortic arch and supra-aortic trunks are extracted from pre-operative magnetic resonance angiography volume. A statistical shape model is computed from these vascular structure iso-centerlines. Euclidean distance between vectors of statistical shape model modes is used to compare endovascular navigation paths. A set of 6 patient cases was used to compute the statistical shape model. For validation, an additional set of 5 patient cases was considered to generate new iso-centerlines.Retrieval of closest iso-centerlines were correct in more than 95% of cases with the proposed method while this percentage goes down to 43% with Euclidean distance between 3D points of iso-centerlines.Clinical relevance-The presented method allows physicians to retrieve past navigation paths similar to a new one. Used in planning, this could allow to anticipate navigation difficulties in mechanical thrombectomy.

Understanding soft-tissue behavior for application to microlaparoscopic surface scan.

This paper presents an approach for understanding the soft-tissue behavior in surface contact with a probe scanning the tissue. The application domain is confocal microlaparoscopy, mostly used for imaging the outer surface of the organs in the abdominal cavity. The probe is swept over the tissue to collect sequential images to obtain a large field of view with mosaicking. The problem we address is that the tissue also moves with the probe due to its softness; therefore, the resulting mosaic is not in the same shape and dimension as traversed by the probe. Our approach is inspired by the finger slip studies and adapts the idea of load-slip phenomenon that explains the movement of the soft part of the finger when dragged on a hard surface. We propose the concept of loading-distance and perform measurements on beef liver and chicken breast tissues. We propose a protocol to determine the loading-distance prior to an automated scan and introduce an approach to compensate the tissue movement in raster scans. Our implementation and experiments show that we can have an image mosaic of the tissue surface in a desired rectangular shape with this approach.

Building large mosaics of confocal edomicroscopic images using visual servoing.

Probe-based confocal laser endomicroscopy provides real-time microscopic images of tissues contacted by a small probe that can be inserted in vivo through a minimally invasive access. Mosaicking consists in sweeping the probe in contact with a tissue to be imaged while collecting the video stream, and process the images to assemble them in a large mosaic. While most of the literature in this field has focused on image processing, little attention has been paid so far to the way the probe motion can be controlled. This is a crucial issue since the precision of the probe trajectory control drastically influences the quality of the final mosaic. Robotically controlled motion has the potential of providing enough precision to perform mosaicking. In this paper, we emphasize the difficulties of implementing such an approach. First, probe-tissue contacts generate deformations that prevent from properly controlling the image trajectory. Second, in the context of minimally invasive procedures targeted by our research, robotic devices are likely to exhibit limited quality of the distal probe motion control at the microscopic scale. To cope with these problems visual servoing from real-time endomicroscopic images is proposed in this paper. It is implemented on two different devices (a high-accuracy industrial robot and a prototype minimally invasive device). Experiments on different kinds of environments (printed paper and ex vivo tissues) show that the quality of the visually servoed probe motion is sufficient to build mosaics with minimal distortion in spite of disturbances.

Design, kinematic optimization, and evaluation of a teleoperated system for middle ear microsurgery.

Middle ear surgery involves the smallest and the most fragile bones of the human body. Since microsurgical gestures and a submillimetric precision are required in these procedures, the outcome can be potentially improved by robotic assistance. Today, there is no commercially available device in this field. Here, we describe a method to design a teleoperated assistance robotic system dedicated to the middle ear surgery. Determination of design specifications, the kinematic structure, and its optimization are detailed. The robot-surgeon interface and the command modes are provided. Finally, the system is evaluated by realistic tasks in experimental dedicated settings and in human temporal bone specimens.

An algorithm for calculi segmentation on ureteroscopic images.

PURPOSE: The purpose of the study is to develop an algorithm for the segmentation of renal calculi on ureteroscopic images. In fact, renal calculi are common source of urological obstruction, and laser lithotripsy during ureteroscopy is a possible therapy. A laser-based system to sweep the calculus surface and vaporize it was developed to automate a very tedious manual task. The distal tip of the ureteroscope is directed using image guidance, and this operation is not possible without an efficient segmentation of renal calculi on the ureteroscopic images. METHODS: We proposed and developed a region growing algorithm to segment renal calculi on ureteroscopic images. Using real video images to compute ground truth and compare our segmentation with a reference segmentation, we computed statistics on different image metrics, such as Precision, Recall, and Yasnoff Measure, for comparison with ground truth. RESULTS: The algorithm and its parameters were established for the most likely clinical scenarii. The segmentation results are encouraging: the developed algorithm was able to correctly detect more than 90% of the surface of the calculi, according to an expert observer. CONCLUSION: Implementation of an algorithm for the segmentation of calculi on ureteroscopic images is feasible. The next step is the integration of our algorithm in the command scheme of a motorized system to build a complete operating prototype.

Thermal and hydrodynamic modelling of active catheters for interventional radiology.

Interventional radiologists desire to improve their operating tools such as catheters. Active catheters in which the tip is moved using shape memory alloy actuators activated using the Joule effect present a promising approach for easier navigation in the small vessels. However, the increase in temperature caused by this Joule effect must be controlled in order to prevent damage to blood cells and tissues. This paper is devoted to the simulation and experimental validation of a fluid-thermal model of an active catheter prototype. Comparisons between computer-predicted and experimentally measured temperatures are presented for both experiments in air and water at 37°C. Good agreement between the computational and experimental results is found, demonstrating the validity of the developed computer model. These comparisons enable us to highlight some important issues in the modelling process and to determine the optimal current for the activation of the catheter.

Robotic hand-held surgical device: evaluation of end-effector's kinematics and development of proof-of-concept prototypes.

We are working towards the development of a robotic hand-held surgical device for laparoscopic interventions that enhances the surgeons' dexterity. In this paper, the kinematics of the end effector is studied. Different choices of kinematics are compared during an evaluation campaign using a virtual reality simulator to find the optimal one: the Yaw-Roll (YR) kinematics. A proof of concept prototype is made based on the results.

Simulation for optimal design of hand-held surgical robots.

Hand-held surgical robots are manipulators with dexterous effectors to be used by surgeons in minimally invasive surgery and especially in laparoscopy. Mechanical manipulators for laparoscopy have appeared on the markets in recent years with various interfaces and dexterities. 2 examples are RealHand and Laparo-Angle. The question of which interface and control mode is the best has not been answered yet. Also, the effector kinematics has not been studied much. We have made a simulator to study the robot's interface, control mode and kinematics to design a hand-held surgical robot for laparoscopic surgery. We asked test subjects to use the simulator and try to make sutures in a virtual environment. Users opinion is that a joystick as interface is easier to use, compared to a jointed interface translating hand's orientation to that of the effector. It appears that a 6 DOF effector coupled to the shaft is necessary and dexterous enough to make sutures in different angles.