Task Autonomy of a Flexible Endoscopic System for Laser-Assisted Surgery

Laser beam steering has been widely studied for the automation of surgery. Currently, flexible instruments for laser surgery are operated entirely by surgeons, which keeps the automation of endoluminal surgery at the initial level. This paper introduces the design of a new workflow that enables the task autonomy of laser-assisted surgery in constrained environments such as the gastrointestinal (GI) tract with a flexible continuum robotic system. Unlike current, laser steering systems driven by piezoelectric require the use of high voltage and are risky. This paper describes a tendon-driven 2 mm diameter flexible manipulator integrated with an endoscope to steer the laser beam. By separating its motion from the total endoscopic system, the designed flexible manipulator can automatically manipulate the laser beam. After the surgical site is searched by the surgeon with a master/slave control, a population-based model-free control method is applied for the flexible manipulator to achieve accurate laser beam steering while overcoming the noise from the visual feedback and disturbances from environment during operation. Simulations and experiments are performed with the system and control methods to demonstrate the proposed framework in a simulated constrained environment.

Deep learning-based monocular placental pose estimation: towards collaborative robotics in fetoscopy

PURPOSE

Twin-to-twin transfusion syndrome (TTTS) is a placental defect occurring in monochorionic twin pregnancies. It is associated with high risks of fetal loss and perinatal death. Fetoscopic elective laser ablation (ELA) of placental anastomoses has been established as the most effective therapy for TTTS. Current tools and techniques face limitations in case of more complex ELA cases. Visualization of the entire placental surface and vascular equator; maintaining an adequate distance and a close to perpendicular angle between laser fiber and placental surface are central for the effectiveness of laser ablation and procedural success. Robot-assisted technology could address these challenges, offer enhanced dexterity and ultimately improve the safety and effectiveness of the therapeutic procedures.

METHODS

This work proposes a 'minimal' robotic TTTS approach whereby rather than deploying a massive and expensive robotic system, a compact instrument is 'robotised' and endowed with 'robotic' skills so that operators can quickly and efficiently use it. The work reports on automatic placental pose estimation in fetoscopic images. This estimator forms a key building block of a proposed shared-control approach for semi-autonomous fetoscopy. A convolutional neural network (CNN) is trained to predict the relative orientation of the placental surface from a single monocular fetoscope camera image. To overcome the absence of real-life ground-truth placenta pose data, similar to other works in literature (Handa et al. in: Proceedings of the IEEE conference on computer vision and pattern recognition, 2016; Gaidon et al. in: Proceedings of the IEEE conference on computer vision and pattern recognition, 2016; Vercauteren et al. in: Proceedings of the IEEE, 2019) the network is trained with data generated in a simulated environment and an in-silico phantom model. A limited set of coarsely manually labeled samples from real interventions are added to the training dataset to improve domain adaptation.

RESULTS

The trained network shows promising results on unseen samples from synthetic, phantom and in vivo patient data. The performance of the network for collaborative control purposes was evaluated in a virtual reality simulator in which the virtual flexible distal tip was autonomously controlled by the neural network.

CONCLUSION

Improved alignment was established compared to manual operation for this setting, demonstrating the feasibility to incorporate a CNN-based estimator in a real-time shared control scheme for fetoscopic applications.

Steerable catheters for minimally invasive surgery: a review and future directions

The steerable catheter refers to the catheter that is manipulated by a mechanism which may be driven by operators or by actuators. The steerable catheter for minimally invasive surgery has rapidly become a rich and diverse area of research. Many important achievements in design, application and analysis of the steerable catheter have been made in the past decade. This paper aims to provide an overview of the state of arts of steerable catheters. Steerable catheters are classified into four main groups based on the actuation principle: (1) tendon driven catheters, (2) magnetic navigation catheters, (3) soft material driven catheters (shape memory effect catheters, steerable needles, concentric tubes, conducting polymer driven catheters and hydraulic pressure driven catheters), and (4) hybrid actuation catheters. The advantages and limitations of each of them are commented and discussed in this paper. The future directions of research are summarized.

From a Disposable Ureteroscope to an Active Lightweight Fetoscope-Characterization and Usability Evaluation

The twin-to-twin transfusion syndrome is a severe fetal anomaly appearing in up to 15% of identical twin pregnancies. This anomaly occurs when twins share blood vessels from a common placenta. The complication leads to an unbalanced blood transfusion between both fetuses. A current surgical treatment consists in coagulating the shared vessels using a fetoscope with an embedded laser. Such treatment is very delicate and constraining due to limited vision and size of the insertion area. The rigidity and lack of controllability of the current used instruments add an additional difficulty and limit the choice in insertion site. This letter proposes an improved flexible fetoscope, offering an enhanced laser controllability and higher versatility regarding the location of the insertion site. A better approach angle can therefore be realized. Also, tissue damage may be further reduced. This single-handed controllable active fetoscope is obtained after adaptation of a LithoVue (Boston Scientific, Natick, MA, USA), a commercially available passive flexible ureteroscope. The LithoVue is fitted with a unique lightweight add-on actuation module foreseen of an artificial muscle and a dedicated control system. Experiments in a mixed reality trainer suggested that the proposed fetoscope is compact, ergonomic, and intuitive in use, allowing an adequate control of the flexible end.

Design, Modelling and Teleoperation of a 2 mm Diameter Compliant Instrument for the da Vinci Platform

This work explores the feasibility of creating and accurately controlling an instrument for robotic surgery with a 2 mm diameter and a three degree-of-freedom (DoF) wrist which is compatible with the da Vinci platform. The instrument's wrist is composed of a two DoF bending notched-nitinol tube pattern, for which a kinematic model has been developed. A base mechanism for controlling the wrist is designed for integration with the da Vinci Research Kit. A basic teleoperation task is successfully performed using two of the miniature instruments. The performance and accuracy of the instrument suggest that creating and accurately controlling a 2 mm diameter instrument is feasible and the design and modelling proposed in this work provide a basis for future miniature instrument development.

Evaluation of fetal tissue viscoelastic characteristics for robotic fetal surgery

PURPOSE

Minimally invasive fetal surgery is expected to improve therapeutic outcomes, and surgical robots are expected to aid the dexterous manipulation of fragile fetal tissues. Although robots are currently used for surgery on soft tissues, practical information concerning the viscoelastic characteristics of fetal tissues is lacking. Hence, the mechanical properties of fetal tissues should be quantified to design robotic devices that facilitate computer-assisted fetal surgery.

METHODS

Shear creep tests were performed on abdominal wall tissues of rat fetuses, aged 16-20 days, and on the brain, lung, and liver tissues of adult rats. Viscoelastic properties of these tissues were evaluated using a rheometer. Histological sections of fetal rat tissues were stained with hematoxylin and eosin.

RESULTS

The viscoelastic properties of fetal tissues were quantified using models. Fetal tissues displayed 2 distinct phases of fragility, i.e., gelatinous characteristics with a markedly lower viscoelasticity before day 18 than after day 19. Concomitantly, skin morphology matured remarkably after day 19. As judged by the morphology, the gestation age of 19 days in rats corresponds to that of 23 weeks in human fetuses. From our data, we prepared artificial phantoms; phantoms made from 1.0% gelatin showed mechanical properties very similar to those of the fetuses before day 18.

CONCLUSION

We observed unique mechanical characteristics in fetal tissue, a previously unknown target for surgical robots. From the data obtained, we produced phantoms that have similar viscoelastic properties, aiming at designing surgical robots capable of handling early fetuses.