Continuum robots provide inherent structural compliance with high dexterity to access the surgical target sites along tortuous anatomical paths under constrained environments and enable to perform complex and delicate operations through small incisions in minimally invasive surgery These advantages enable their broad applications with minimal trauma and make challenging clinical procedures possible with miniaturized instrumentation and high curvilinear access capabilities However, their inherent deformable designs make it difficult to realize 3-D intraoperative real-time shape sensing to accurately model their shape Solutions to this limitation can lead themselves to further develop closely associated techniques of closed-loop control, path planning, human–robot interaction, and surgical manipulation safety concerns in minimally invasive surgery Although extensive model-based research that relies on kinematics and mechanics has been performed, accurate shape sensing of continuum robots remains challenging, particularly in cases of unknown and dynamic payloads This survey investigates the recent advances in alternative emerging techniques for 3-D shape sensing in this field and focuses on the following categories: fiber-optic-sensor-based, electromagnetic-tracking-based, and intraoperative imaging modality-based shape-reconstruction methods The limitations of existing technologies and prospects of new technologies are also discussed

Shape Sensing Techniques for Continuum Robots in Minimally Invasive Surgery: A Survey

Background

Remote-controlled catheter navigation systems have recently been introduced into minimally invasive vascular surgery and some of them have already been applied in clinical practice. Steerable catheters with improved manoeuvrability play an important role in these innovations for conventional catheterization.



Methods

This review details the development of various steerable catheters, both in use clinically and under investigation. Comprehensive comparison and analysis in several key aspects are followed to reveal both the advantages and limitations of these catheters, as well as the requirements for relevant techniques.



Results

Steerable catheters are able to select direction in the distal end, and superior to conventional counterparts in many aspects. Differences between magnetic and active catheters mainly lie in function, safety, configuration of operating room and cost. They have similar requirements for miniaturization and slave insertion mechanisms.



Conclusions

Steerable catheters are rapidly evolving and still require technological refinements to extend current capabilities. Copyright © 2009 John Wiley & Sons, Ltd.

Steerable catheters in minimally invasive vascular surgery.

Remote-controlled vascular interventional robots (RVIRs) are being developed to increase the overall accuracy of surgical operations and reduce the occupational risks of intervening physicians, such as radiation exposure and chronic neck/back pain. Several RVIRs have been used to operate catheters or guidewires accurately. However, a lack of cooperation between the catheters and guidewires results in the surgeon being unable to complete complex surgery by propelling the catheter/guidewire to the target position. Furthermore, it is a significant challenge to operate the catheter/guidewire accurately and detect their proximal force without damaging their surfaces. In this study, we introduce a novel method that allows catheters and guidewires to be operated simultaneously in complex surgery. Our method accurately captures force measurements and enables precisely controlled catheter and guidewire operation. A prototype is validated through various experiments. The results demonstrate the feasibility of the proposed RVIR to operate a catheter and guidewire accurately, detect the resistance forces, and complete complex surgical operations in a cooperative manner.

A cooperation of catheters and guidewires-based novel remote-controlled vascular interventional robot

This paper proposes a master-slave catheterisation system including a steerable catheter with positioning function and an insertion mechanism with force feedback. The steerable catheter is integrated with two magnetic tracking sensors for positioning. The distal shape of catheter is displayed with virtual vascular model to generate 3D guiding image to provide the relative relationship between the catheter and its surrounding vessels. The master-slave insertion mechanism with differential gear structure is designed with force feedback to assist surgeons to manipulate the catheter. It can implement pulling/pushing, rotating and bending/recovering the catheter. Based on this system, surgeons in the control room can utilise the master handle to operate the insertion mechanism for positioning the distal end of catheter with the assistance of 3D guiding image. The stability and accuracy of the system is validated in-vitro.

The master-slave catheterisation system for positioning the steerable catheter

This paper presents a robotic catheter system with force sensors, monitor and a master-slave remote control system. We developed micro force sensors and applied them in the system to guarantee the operation safety in intravascular neurosurgery applications, and employed a camera to monitor the operation. Two kinds of force information are obtained through force sensors when the catheter contacted the blood vessel. The experiment shows that the proposed force sensors-based catheter system works well through force feedback and remote control. The system can facilitates the operation and avoid potential damages.

A robotic catheter system with real-time force feedback and monitor.

Background

The emergence of the active catheter has prompted the development of catheterization in minimally invasive surgery. However, it is still operated using only the physician's vision; information supplied by the guiding image and tracking sensors has not been fully utilized.



Methods

In order to supply the active catheter with more useful information for automatic navigation, we extract the skeleton of blood vessels by means of an improved distance transform method, and then present the crucial geometric information determining navigation. With the help of tracking sensors' position and pose information, two operations, advancement in the proximal end and direction selection in the distal end, are alternately implemented to insert the active catheter into a target blood vessel.



Results

The skeleton of the aortic arch reconstructed from slice images is extracted fast and automatically. A navigation path is generated on the skeleton by manually selecting the start and target points, and smoothed with the cubic cardinal spline curve. Crucial geometric information determining navigation is presented, as well as requirements for the catheter entering the target blood vessel. Using a shape memory alloy active catheter integrated with magnetic sensors, an experiment is carried out in a vascular model, in which the catheter is successfully inserted from the ascending aorta, via the aortic arch, into the brachiocephalic trunk.



Conclusions

The navigation strategy proposed in this paper is feasible and has the advantage of increasing the automation of catheterization, enhancing the manoeuvrability of the active catheter and providing the guiding image with desirable interactivity. Copyright © 2009 John Wiley & Sons, Ltd.

Wei Deng

Papers

Skeleton-based active catheter navigation.