37 research outputs found
Enhanced real-time pose estimation for closed-loop robotic manipulation of magnetically actuated capsule endoscopes
Pose estimation methods for robotically guided magnetic actuation of capsule endoscopes have recently enabled trajectory following and automation of repetitive endoscopic maneuvers. However, these methods face significant challenges in their path to clinical adoption including the presence of regions of magnetic field singularity, where the accuracy of the system degrades, and the need for accurate initialization of the capsule's pose. In particular, the singularity problem exists for any pose estimation method that utilizes a single source of magnetic field if the method does not rely on the motion of the magnet to obtain multiple measurements from different vantage points. We analyze the workspace of such pose estimation methods with the use of the point-dipole magnetic field model and show that singular regions exist in areas where the capsule is nominally located during magnetic actuation. Since the dipole model can approximate most magnetic field sources, the problem discussed herein pertains to a wider set of pose estimation techniques. We then propose a novel hybrid approach employing static and time-varying magnetic field sources and show that this system has no regions of singularity. The proposed system was experimentally validated for accuracy, workspace size, update rate and performance in regions of magnetic singularity. The system performed as well or better than prior pose estimation methods without requiring accurate initialization and was robust to magnetic singularity. Experimental demonstration of closed-loop control of a tethered magnetic device utilizing the developed pose estimation technique is provided to ascertain its suitability for robotically guided capsule endoscopy. Hence, advances in closed-loop control and intelligent automation of magnetically actuated capsule endoscopes can be further pursued toward clinical realization by employing this pose estimation system
Enabling the future of colonoscopy with intelligent and autonomous magnetic manipulation
Early diagnosis of colorectal cancer substantially improves survival. However, over half of cases are diagnosed late due to the demand for colonoscopy—the ‘gold standard’ for screening—exceeding capacity. Colonoscopy is limited by the outdated design of conventional endoscopes, which are associated with high complexity of use, cost and pain. Magnetic endoscopes are a promising alternative and overcome the drawbacks of pain and cost, but they struggle to reach the translational stage as magnetic manipulation is complex and unintuitive. In this work, we use machine vision to develop intelligent and autonomous control of a magnetic endoscope, enabling non-expert users to effectively perform magnetic colonoscopy in vivo. We combine the use of robotics, computer vision and advanced control to offer an intuitive and effective endoscopic system. Moreover, we define the characteristics required to achieve autonomy in robotic endoscopy. The paradigm described here can be adopted in a variety of applications where navigation in unstructured environments is required, such as catheters, pancreatic endoscopy, bronchoscopy and gastroscopy. This work brings alternative endoscopic technologies closer to the translational stage, increasing the availability of early-stage cancer treatments
Characterisation and State Estimation of Magnetic Soft Continuum Robots
Minimally invasive surgery has become more popular as it leads to less bleeding, scarring, pain, and shorter recovery time. However, this has come with counter-intuitive devices and steep surgeon learning curves. Magnetically actuated Soft Continuum Robots (SCR) have the potential to replace these devices, providing high dexterity together with the ability to conform to complex environments and safe human interactions without the cognitive burden for the clinician. Despite considerable progress in the past decade in their development, several challenges still plague SCR hindering their full realisation. This thesis aims at improving magnetically actuated SCR by addressing some of these challenges, such as material characterisation and modelling, and sensing feedback and localisation.
Material characterisation for SCR is essential for understanding their behaviour and designing effective modelling and simulation strategies. In this work, the material properties of commonly employed materials in magnetically actuated SCR, such as elastic modulus, hyper-elastic model parameters, and magnetic moment were determined. Additionally, the effect these parameters have on modelling and simulating these devices was investigated.
Due to the nature of magnetic actuation, localisation is of utmost importance to ensure accurate control and delivery of functionality. As such, two localisation strategies for magnetically actuated SCR were developed, one capable of estimating the full 6 degrees of freedom (DOFs) pose without any prior pose information, and another capable of accurately tracking the full 6-DOFs in real-time with positional errors lower than 4~mm. These will contribute to the development of autonomous navigation and closed-loop control of magnetically actuated SCR
Control of Magnetic Continuum Robots for Endoscopy
The present thesis discusses the problem of magnetic actuation and control applied to
millimetre-scale robots for endoluminal procedures. Magnetic actuation, given its remote
manipulation capabilities, has the potential to overcome several limitations of current endoluminal
procedures, such as the relatively large size, high sti�ness and limited dexterity
of existing tools. The application of functional forces remotely facilitates the development
of softer and more dexterous endoscopes, which can navigate with reduced discomfort for
the patient. However, the solutions presented in literature are not always able to guarantee
smooth navigation in complex and convoluted anatomical structures. This thesis
aims at improving the navigational capabilities of magnetic endoluminal robots, towards
achieving full autonomy. This is realized by introducing novel design, sensing and control
approaches for magnetically actuated soft endoscopes and catheters.
First, the application of accurate closed-loop control to a 1 Internal Permanent Magnet
(IPM) endoscope was analysed. The proposed approach can guarantee better navigation
capabilities, thanks to the manipulation of every mechanical Degree of Freedom (DOF)
- 5 DOFs. Speci�cally, it was demonstrated that gravity can be balanced with su�cient
accuracy to guarantee tip levitation. In this way contact is minimized and obstacle
avoidance improved. Consequently, the overall navigation capabilities of the endoscope
were enhanced for given application.
To improve exploration of convoluted anatomical pathways, the design of magnetic endoscopes
with multiple magnetic elements along their length was introduced. This approach
to endoluminal device design can ideally allow manipulation along the full length; facilitating
full shape manipulation, as compared to tip-only control. To facilitate the control
of multiple magneto-mechanical DOFs along the catheters' length, a magnetic actuation
method was developed based on the collaborative robotic manipulation of 2 External
Permanent Magnets (EPMs). This method, compared to the state-of-the-art, facilitates
large workspace and applied �eld, while guaranteeing dexterous actuation. Using this approach,
it was demonstrated that it is possible to actuate up to 8 independent magnetic
DOFs.
In the present thesis, two di�erent applications are discussed and evaluated, namely:
colonoscopy and navigational bronchoscopy. In the former, a single-IPM endoscopic approach
is utilized. In this case, the anatomy is large enough to permit equipping the endoscope
with a camera; allowing navigation by direct vision. Navigational bronchoscopy,
on-the-other-hand, is performed in very narrow peripheral lumina, and navigation is informed
via pre-operative imaging. The presented work demonstrates how the design of
the magnetic catheters, informed by a pre-operative Computed Tomography (CT) scan,
can mitigate the need for intra-operative imaging and, consequently, reduce radiation
exposure for patients and healthcare workers. Speci�cally, an optimization routine to
design the catheters is presented, with the aim of achieving follow-the-leader navigation
without supervision.
In both scenarios, analysis of how magnetic endoluminal devices can improve the current
practice and revolutionize the future of medical diagnostics and treatment is presented
and discussed
Closed-Loop Magnetic Manipulation for Robotic Transesophageal Echocardiography
This paper presents a closed-loop magnetic manipulation framework for robotic
transesophageal echocardiography (TEE) acquisitions. Different from previous
work on intracorporeal robotic ultrasound acquisitions that focus on continuum
robot control, we first investigate the use of magnetic control methods for
more direct, intuitive, and accurate manipulation of the distal tip of the
probe. We modify a standard TEE probe by attaching a permanent magnet and an
inertial measurement unit sensor to the probe tip and replacing the flexible
gastroscope with a soft tether containing only wires for transmitting
ultrasound signals, and show that 6-DOF localization and 5-DOF closed-loop
control of the probe can be achieved with an external permanent magnet based on
the fusion of internal inertial measurement and external magnetic field sensing
data. The proposed method does not require complex structures or motions of the
actuator and the probe compared with existing magnetic manipulation methods. We
have conducted extensive experiments to validate the effectiveness of the
framework in terms of localization accuracy, update rate, workspace size, and
tracking accuracy. In addition, our results obtained on a realistic cardiac
tissue-mimicking phantom show that the proposed framework is applicable in real
conditions and can generally meet the requirements for tele-operated TEE
acquisitions.Comment: Accepted by IEEE Transactions on Robotics. Copyright may be
transferred without notice, after which this version may no longer be
accessibl
Soft Robot-Assisted Minimally Invasive Surgery and Interventions: Advances and Outlook
Since the emergence of soft robotics around two decades ago, research interest in the field has escalated at a pace. It is fuelled by the industry's appreciation of the wide range of soft materials available that can be used to create highly dexterous robots with adaptability characteristics far beyond that which can be achieved with rigid component devices. The ability, inherent in soft robots, to compliantly adapt to the environment, has significantly sparked interest from the surgical robotics community. This article provides an in-depth overview of recent progress and outlines the remaining challenges in the development of soft robotics for minimally invasive surgery
Active Stabilization of Interventional Tasks Utilizing a Magnetically Manipulated Endoscope
Magnetically actuated robots have become increasingly popular in medical endoscopy over the past decade. Despite the significant improvements in autonomy and control methods, progress within the field of medical magnetic endoscopes has mainly been in the domain of enhanced navigation. Interventional tasks such as biopsy, polyp removal, and clip placement are a major procedural component of endoscopy. Little advancement has been done in this area due to the problem of adequately controlling and stabilizing magnetically actuated endoscopes for interventional tasks. In the present paper we discuss a novel model-based Linear Parameter Varying (LPV) control approach to provide stability during interventional maneuvers. This method linearizes the non-linear dynamic interaction between the external actuation system and the endoscope in a set of equilibria, associated to different distances between the magnetic source and the endoscope, and computes different controllers for each equilibrium. This approach provides the global stability of the overall system and robustness against external disturbances. The performance of the LPV approach is compared to an intelligent teleoperation control method (based on a Proportional Integral Derivative (PID) controller), on the Magnetic Flexible Endoscope (MFE) platform. Four biopsies in different regions of the colon and at two different system equilibria are performed. Both controllers are asked to stabilize the endoscope in the presence of external disturbances (i.e. the introduction of the biopsy forceps through the working channel of the endoscope). The experiments, performed in a benchtop colon simulator, show a maximum reduction of the mean orientation error of the endoscope of 45.8% with the LPV control compared to the PID controller
Robotic, self-propelled, self-steerable, and disposable colonoscopes: Reality or pipe dream? A state of the art review.
Robotic colonoscopes could potentially provide a comfortable, less painful and safer alternative to standard colonoscopy. Recent exciting developments in this field are pushing the boundaries to what is possible in the future. This article provides a comprehensive review of the current work in robotic colonoscopes including self-propelled, steerable and disposable endoscopes that could be alternatives to standard colonoscopy. We discuss the advantages and disadvantages of these systems currently in development and highlight the technical readiness of each system to help the reader understand where and when such systems may be available for routine clinical use and get an idea of where and in which situation they can best be deployed