In this paper, we describe the state of the art in continuum robot manipulators and systems intended for application to interventional medicine. Inspired by biological trunks, tentacles, and snakes, continuum robot designs can traverse confined spaces, manipulate objects in complex environments, and conform to curvilinear paths in space. In addition, many designs offer inherent structural compliance and ease of miniaturization. After decades of pioneering research, a host of designs have now been investigated and have demonstrated capabilities beyond the scope of conventional rigid-link robots. Recently, we have seen increasing efforts aimed at leveraging these qualities to improve the frontiers of minimally invasive surgical interventions. Several concepts have now been commercialized, which are inspiring and enabling a current paradigm shift in surgical approaches toward flexible access routes, e.g., through natural orifices such as the nose. In this paper, we provide an overview of the current state of this field from the perspectives of both robotics science and medical applications. We discuss relevant research in design, modeling, control, and sensing for continuum manipulators, and we highlight how this work is being used to build robotic systems for specific surgical procedures. We provide perspective for the future by discussing current limitations, open questions, and challenges.

Continuum Robots for Medical Applications: A Survey

Small-scale soft continuum robots capable of active steering and navigation in a remotely controllable manner hold great promise in diverse areas, particularly in medical applications. Existing continuum robots, however, are often limited to millimeter or centimeter scales due to miniaturization challenges inherent in conventional actuation mechanisms, such as pulling mechanical wires, inflating pneumatic or hydraulic chambers, or embedding rigid magnets for manipulation. In addition, the friction experienced by the continuum robots during navigation poses another challenge for their applications. Here, we present a submillimeter-scale, self-lubricating soft continuum robot with omnidirectional steering and navigating capabilities based on magnetic actuation, which are enabled by programming ferromagnetic domains in its soft body while growing hydrogel skin on its surface. The robot's body, composed of a homogeneous continuum of a soft polymer matrix with uniformly dispersed ferromagnetic microparticles, can be miniaturized below a few hundreds of micrometers in diameter, and the hydrogel skin reduces the friction by more than 10 times. We demonstrate the capability of navigating through complex and constrained environments, such as a tortuous cerebrovascular phantom with multiple aneurysms. We further demonstrate additional functionalities, such as steerable laser delivery through a functional core incorporated in the robot's body. Given their compact, self-contained actuation and intuitive manipulation, our ferromagnetic soft continuum robots may open avenues to minimally invasive robotic surgery for previously inaccessible lesions, thereby addressing challenges and unmet needs in healthcare.

Ferromagnetic soft continuum robots

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

Endovascular techniques have been embraced as a minimally-invasive treatment approach within different disciplines of interventional radiology and cardiology. The current practice of endovascular procedures, however, is limited by a number of factors including exposure to high doses of X-ray radiation, limited 3D imaging, and lack of contact force sensing from the endovascular tools and the vascular anatomy. More recently, advances in steerable catheters and development of master/slave robots have aimed to improve these practices by removing the operator from the radiation source and increasing the precision and stability of catheter motion with added degrees-of-freedom. Despite their increased application and a growing research interest in this area, many such systems have been designed without considering the natural manipulation skills and ergonomic preferences of the operators. Existing studies on tool interactions and natural manipulation skills of the operators are limited. In this manuscript, new technical developments in different aspects of robotic endovascular intervention including catheter instrumentation, intra-operative imaging and navigation techniques, as well as master/slave based robotic catheterization platforms are reviewed. We further address emerging trends and new research opportunities towards more widespread clinical acceptance of robotically assisted endovascular technologies.

Current and emerging robot-assisted endovascular catheterization technologies: a review.

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.

The invention relates to a catheter intervention device with the conveying resistance feedback function, belonging to a catheter intervention device, and aiming at solving the problems that the existing catheter intervention device is not compact in structure, does not have the conveying resistance feedback function and is operated at the surgical site by doctors getting involved the surgery. Output shafts of a left and a right motors are fixedly sheathed with a left side driving gear and a first-stage driving gear; the left side driving gear is meshed with a left side driven gear; the first-stage driving gear is meshed with a first-stage driven gear; a second-stage driving bevel gear is fixedly connected with the first-stage driven gear; the second-stage driving bevel gear is meshed witha second-stage driven bevel gear; a third-stage driving gear is fixedly connected with the second-stage driven bevel gear; the third-stage driving gear is meshed with a third-stage driven gear; a driving friction inner wheel is fixedly provided with a touch force sensor; the driving friction inner wheel is connected with a driving friction outer wheel by the touch force sensor; a signal output end of the touch force sensor is connected with a signal input end of an amplification circuit board; and an amplifying signal output end of the amplification circuit board is connected with a signal input end of an inner ring of a second electric conduction sliding ring. The catheter intervention device is used for continuously conveying a catheter and feedback of the force.

Catheter intervention device with conveying resistance feedback function

The objective of this study is to provide catheterization with a three-dimensional (3D) guiding image and reduce the collision probability between the catheter tip and vascular wall. A bidirectional steerable catheter was integrated with two magnetic position-tracking sensors on both sides of its bending segment. The tracking information was displayed on the guiding image, which helped the surgeons to determine the relative position between the catheter tip and surrounding vessels. The navigation path was generated on the basis of the vascular skeleton. Moreover, along the path, a series of guiding circular planes were set as the guidance for the catheter. Three operations (bending, advancing, and twisting) were jointly conducted to get the catheter through these guiding planes in turn and eventually into the target vessel. The effectiveness of the proposed navigation method was verified by experiments implemented in an aorta vascular phantom. The navigation system has a mean error of 0.19 mm, a r...

An in vitro investigation of image-guided steerable catheter navigation.

In this paper, a micro bending robot (MBR) for an active catheter which allows any bending direction and bending angle and has a simple structure for miniaturization was developed. The MBR is 1.25 mm in outer diameter. In order to achieve a large bending angle meanwhile not to increase the outer diameter of the MBR too much, the MBR consists of 3 bending units. A bending unit consists of a bias spring and 3 incorporating shape memory alloy (SMA) coil actuators. The bending model of a bending unit was established based on a design chart and equation. Kinematics of a bending unit was analysed, and the position and orientation of the tip center and the displacements of all 3 SMA coil actuators of the bending unit in any bending direction and bending angle were obtained. Finally, the position and orientation of the tip center of the MBR and its bending angle in any bending direction were deduced. The works of this paper help to consummate the design theory of active catheter and has important theoretic significance and practical applied value.

Kinematics of Micro Bending Robot Using Shape Memory Alloy for Active Catheter

The invention provides an automatic navigation method for a catheter. The invention relates to the automatic navigation method for the catheter, which is applied to a minimally-invasive intervention surgery for guiding the catheter to reach a lesion part automatically, so as to overcome the defect that the previous technology totally depends on vision and decision of doctors. A front end and a back end of a steering section at the distal end of an active catheter are respectively integrated into a position sensor. The method comprises the following steps: 1. a skeleton of a blood vessel is used for generating a navigation path, and a plurality of guiding planes are arranged along the navigation path, wherein, the guiding planes are a serial of discrete round planes which take points on the navigation path as circle centers and are vertical to the navigation path; 2. during the blood vessel intervention process of the catheter, the catheter is controlled to sequentially pass the guiding planes arranged in the first step to a target location. The movement of the catheter comprises two alternate operations of propulsion and direction selection. During the propulsion, the position sensor continuously collects the position of the endpoint of the distal end of the catheter, so that the direction vectors of the steering section point to the inside of the guiding planes and are intersected in the circle centers.

Automatic guidance method of catheter

The effect of green tea administration on serum lipids' concentrations remains unclear as various investigations, which have explored this topic, have produced conflicting results. Gender might be one of the factors influencing the impact of green tea on the lipid profile. Hence, we conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to assess the effect of green tea intake on the lipid profile in overweight and obese women. We searched five databases (Web of Science, SCOPUS, Embase, PubMed/Medline, and Google Scholar) using a combination of MeSH and non-MeSH terms. Results were expressed as weighted mean differences (WMDs) and 95% confidence intervals (CIs) and synthesized with a random-effects model. In total, 15 eligible RCTs with 16 arms (1818 participants) were included in the meta-analysis. The combined effect size revealed a significant reduction in total cholesterol (TC) (WMD: -4.45 mg/dl, 95% CI: -6.63, -2.27, P<0.001) and low-density lipoprotein cholesterol (LDL-C) (WMD: -4.49 mg/dl, 95% CI: -7.50 to -1.47, P=0.003) concentrations following green tea supplementation in overweight and/or obese women. In addition, a more pronounced reduction of triglyceride (TG) levels occurred when the baseline TG value was ≥150 mg/dL (WMD: -24.45 mg/dL, 95% CI: -40.63 to -8.26, P=0.003). Moreover, a significant decrease in TG concentrations occurred in RCTs conducted on overweight subjects (BMI: 25-29.99 kg/m2) (WMD: -5.88 mg/dl, 95% CI: -10.76 to -0.99, P=0.01). In the subgroup analyses based on the study population, a notable increase in high-density lipoprotein cholesterol (HDL-C) values was observed in obese individuals (>30 kg/m2) (WMD: 2.63 mg/dl, 95% CI: 0.10 to 5.16, P=0.041). Consumption of green tea causes a reduction in LDL-C and TC concentrations in overweight and obese women. The decline in TG levels was notable particularly in overweight patients with hypertriglyceridemia at baseline. In addition, a significant increase in HDL-C was detected in obese subjects following intake of green tea.

Zhaoguang Liang

Papers

Catheter intervention device with conveying resistance feedback function

An in vitro investigation of image-guided steerable catheter navigation.

Kinematics of Micro Bending Robot Using Shape Memory Alloy for Active Catheter

Automatic guidance method of catheter

Effects of green tea on lipid profile in overweight and obese women.