Piotr R. Slawinski

Capsule endoscopy of the future: What's on the horizon?

Capsule endoscopes have evolved from passively moving diagnostic devices to actively moving systems with potential therapeutic capability. In this review, we will discuss the state of the art, define the current shortcomings of capsule endoscopy, and address research areas that aim to overcome said shortcomings. Developments in capsule mobility schemes are emphasized in this text, with magnetic actuation being the most promising endeavor. Research groups are working to integrate sensor data and fuse it with robotic control to outperform todays standard invasive procedures, but in a less intrusive manner. With recent advances in areas such as mobility, drug delivery, and therapeutics, we foresee a translation of interventional capsule technology from the bench-top to the clinical setting within the next 10 years.

Intestinal biomechanics simulator for robotic capsule endoscope validation

Abstract This work describes the development and validation of a novel device which simulates important forces experienced by Robotic Capsule Endoscopes (RCE) in vivo in the small intestine. The purpose of the device is to expedite and lower the cost of RCE development. Currently, there is no accurate in vitro test method nor apparatus to validate new RCE designs; therefore, RCEs are tested in vivo at a cost of ∼

Closed Loop Control of a Tethered Magnetic Capsule Endoscope

1400 per swine test. The authors have developed an in vitro RCE testing device which generates two peristaltic waves to accurately simulate the two biomechanical actions of the human small intestine that are most relevant to RCE locomotion: traction force and contact force. The device was successfully calibrated to match human physiological ranges for traction force (4–40 gf), contact force (80–500 gf) and peristaltic wave propagation speed (0.08–2 cm s−1) for a common RCE capsule geometry of 3.5 cm length and 1.5 cm diameter.

Nonholonomic closed-loop velocity control of a soft-tethered magnetic capsule endoscope

Magnetic field gradients have repeatedly been shown to be the most feasible mechanism for gastrointestinal capsule endoscope actuation. An inverse quartic magnetic force variation with distance results in large force gradients induced by small movements of a driving magnet; this necessitates robotic actuation of magnets to implement stable control of the device. A typical system consists of a serial robot with a permanent magnet at its end effector that actuates a capsule with an embedded permanent magnet. We present a tethered capsule system where a capsule with an embedded magnet is closed loop controlled in 2 degree-of-freedom in position and 2 degree-of-freedom in orientation. Capitalizing on the magnetic field of the external driving permanent magnet, the capsule is localized in 6-D allowing for both position and orientation feedback to be used in a control scheme. We developed a relationship between the serial robots joint parameters and the magnetic force and torque that is exerted onto the capsule. Our methodology was validated both in a dynamic simulation environment where a custom plug-in for magnetic interaction was written, as well as on an experimental platform. The tethered capsule was demonstrated to follow desired trajectories in both position and orientation with accuracy that is acceptable for colonoscopy.

Enhanced real-time pose estimation for closed-loop robotic manipulation of magnetically actuated capsule endoscopes

In this paper, we demonstrate velocity-level closed-loop control of a tethered magnetic capsule endoscope that is actuated via serial manipulator with a permanent magnet at its end-effector. Closed-loop control (2 degrees-of-freedom in position, and 2 in orientation) is made possible with the use of a real-time magnetic localization algorithm that utilizes the actuating magnetic field and thus does not require additional hardware. Velocity control is implemented to create smooth motion that is clinically necessary for colorectal cancer diagnostics. Our control algorithm generates a spline that passes through a set of input points that roughly defines the shape of the desired trajectory. The velocity controller acts in the tangential direction to the path, while a secondary position controller enforces a nonholonomic constraint on capsule motion. A soft nonholonomic constraint is naturally imposed by the lumen while we enforce a strict constraint for both more accurate estimation of tether disturbance and hypothesized intuitiveness for a clinicians teleoperation. An integrating disturbance force estimation control term is introduced to predict the disturbance of the tether. This paper presents the theoretical formulations and experimental validation of our methodology. Results show the systems ability to achieve a repeatable velocity step response with low steady-state error as well as ability of the tethered capsule to maneuver around a bend.

The first autonomously controlled magnetic flexible endoscope for colon exploration

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. As 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.

Towards Recovering a Lost Degree of Freedom in Magnet-Driven Robotic Capsule Endoscopy

© 2018 by the AGA Institute 0016-5085/

Laparoscopic Camera Based on an Orthogonal Magnet Arrangement

36.00 https://doi.org/10.1053/j.gastro.2018.02.037 Tuse since the 1950s, rely on rear-push mechanical actuation to advance through the gastrointestinal tract. This necessitates a semirigid insertion tube to prevent buckling that may induce patient discomfort or trauma owing to tissue stress. To overcome this limitation, magnetic fields have been used for endoscope actuation. Unfortunately, manual operation of magnetic actuation is not intuitive and, therefore, computer assistance has been shown to be beneficial. The use of computers and robotics facilitates autonomy, which may be used to assist the operator during repetitive or complex maneuvers through relief of cognitive burden and potential learning curve reduction. In our academic laboratory, we have developed a highly compliant magnetic flexible endoscope (MFE) platform (with diagnostic and therapeutic capability) that relies on actuation using an actuating permanent magnet (APM) manipulated by a robot that is external to the patient; thus, it does not require push actuation. Using proprioceptive sensing and software algorithms, we are able to control MFE motion and enact autonomous function. Within endoscopy, colonoscopy is ripe for autonomous control owing to the repetitive nature of some maneuvers and the skill/experience necessary to achieve excellent technique. We focus our demonstration of autonomy on retroflexion because it is a common endoscopic maneuver that is skill intensive, repetitive, and technically challenging when using magnetic actuation. The ability to safely retroflex the MFE in any area of the colon may potentially increase polyp detection and reduce the incidence of colorectal cancer. Our team has developed an autonomous control algorithm for MFE retroflexion. We conducted 30 autonomous retroflexions in vivo in a 40-kg female Yorkshire-Landrace cross swine (Supplementary Material: Retroflexion study design). All of the autonomous retroflexion maneuvers were successful (100%; n 1⁄4 30) with a mean maneuver time of 11.3 ± 2.4 seconds. The visible difference in trajectories and difference in APM position respective to the starting point indicate that the APM did not follow a precomputed trajectory, but was instead autonomously reacting to external input, in this case the MFE’s motion (Video Clip 1). All of the trials in this study were completed without tissue

Performance Assessment of a Noninvasive Swallowable Biosensor Deployment System in Microgravity

Flexible endoscopy, a procedure during which an operator pushes a semi-rigid endoscope through a patient’s gastrointestinal tract, has been the gold-standard screening method for colon cancer screening (colonoscopy) for over 50 years. Owing to the large amounts of tissue stress that result from the need for transmitting a force to the tip of the endoscope while the device wraps through the bowel, implementing a front-actuated endoscopy system has been a popular area of research [1]. The pursuit of such a concept was accelerated by the advent of ingestible capsule endoscopes, which, since then, have been augmented by researchers to include therapeutic capabilities, modalities for maneuverability, amongst other diagnostic functions [2]. One of the more common approaches investigated has been the use of magnetic fields to apply forces and torques to steer the tip of an endoscope [3]. Recent efforts in magnetic actuation have resulted in the use of robot manipulators with permanent magnets at their end effectors that are used to manipulate endoscopes with embedded permanent magnets. Recently, we implemented closed loop control of a tethered magnetic capsule by using real-time magnetic localization and the linearization of a magnetic wrench applied to the capsule by the actuating magnet [4]. This control was implemented in 2 degrees-of-freedom (DoF) in position (in the horizontal plane) and 2 DoF in orientation (panning and tilting). One DoF in position is lost owing to the tethered capsule being actuated in air and thus lacking a restoring force to counter the high field gradient. The 3rd orientation DoF is lost owing to the axial symmetry of the permanent magnet in the capsule; this prevents the application of torque in the axial direction and thus controlled roll and introduces a singularity in the capsule’s actuation. Although another dipole could be used to eliminate this singularity, this would complicate both the actuation and localization methods. In this manuscript, we consider the consequences of the embedded magnet (EM) being radially offset from the center of the capsule while being manipulated by an external actuating magnet (AM).We have developed a tethered capsule endoscope that contains a cylindrical EM (11.11 mm in length and diameter) with a residual flux density of 1.48 T that is offset by 1.85 mm from the center of the capsule; a distance that is less than 10% of the capsule diameter. Our investigation into the topic results from repeated observation of the capsule’s preference to align such that the internal magnet is closest to the actuating magnet (AM). The AM is a cylindrical magnet (101.6 mm in length and diameter) with a residual flux density of 1.48 T that is mounted at the end effector of a 6 DoF manipulator, as seen in Figure 1. In this manuscript, we evaluate the torqueing effects of the presence of this magnet offset with the goal of determining whether the torque effect is negligible, or impacts capsule motion and thus can potentially be used for the benefit of endoscope manipulation. A concept schematic of this effect is shown in Figure 2. A discussion of how to use this torque is beyond the scope of this manuscript. To the authors’ knowledge, the use of such concept in permanent-magnet based control has not been investigated.

Emerging Issues and Future Developments in Capsule Endoscopy.

In this letter, we present for the first time a magnetic anchoring-actuation link with an auto-flip feature. This orthogonal magnetic arrangement relies on the placement of two permanent magnets such that their magnetic moments are respectfully orthogonal. Though the arrangement may have many applications, in this study we integrate it in a small factor magnetic camera for minimally invasive procedures. Upon insertion through a trocar incision, the 5.5 mm diameter and 35 mm length magnetic camera is coupled with an external robotic controller and displaced from the port thus preventing clutter of the surgical workspace. The device allows for manual lateral translation as well as robotically controlled tilt and pan, resulting in four degrees of freedom. The auto-flip feature prevents the need for image adjustment in software as the camera tilts through its hemispherical workspace. A static model that relates an input external control tilt and output camera tilt has been developed and validated. Favorable results during bench and canine cadaver evaluation suggest promise for the proposed magnetic camera to improve the state of art in minimally invasive surgical procedures.