Tendon-assisted magnetically steered (TAMS) robotic delivery device

Abstract

A tendon-assisted magnetically steered robotic delivery device may include a distal tip including a plurality of tendon-routing disks, and a plurality of magnetic spherical joints.

Description

TENDON-ASSISTED MAGNETICALLY STEERED (TAMS) ROBOTIC DELIVERY DEVICECROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 542,638, filed on October 5, 2023, the entire contents of which are incorporated herein by reference.BACKGROUND

[0002] This disclosure relates to robotic guidance systems for use in medical procedures. More specifically, this disclosure relates to tendon-assisted, magnetically steered robotic guidance systems.SUMMARY

[0003] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device including: a distal tip including a plurality of tendon-routing disks, and a plurality of magnetic spherical joints.

[0004] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, further including a stem including tendon routing channels, wherein the stem is formed of ni tinol.

[0005] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, further including a stem including tendon routing channels, wherein the stem defines an internal diameter of more than 1 mm and an outside diameter of less than 1.4 mm.

[0006] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, further including a stem including tendon routing channels, wherein the stem is formed of a non-magnetic material.

[0007] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, wherein each of the plurality of tendon-routing disks are positioned between two of the plurality of magnetic spherical joints.

[0008] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, wherein the distal tip defines two degrees-of-freedom between any two adjacent tendon-routing disks.

[0009] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, further including: further including a stem including tendon routing channels; and three tendons coupled to the distal tip through the stem, the three tendons structured to actuate the distal tip.

[0010] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, wherein each of the plurality of tendon-routing disks includes three routing holes, each of the routing holes structured to receive one of the three tendons.

[0011] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, further including a fourth tendon coupled to the distal tip through the stem, the fourth tendon structured to actuate the distal tip.

[0012] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, wherein each of the plurality of tendon-routing disks includes a fourth routing hole, each of the fourth routing holes structured to receive the fourth tendon.

[0013] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, further including two motors coupled to the four tendons and structured to actuate the tendons.

[0014] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, further including four motors coupled to the four tendons and structured to actuate the tendons.

[0015] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, further including four load cells, wherein each load cell is coupled between a tendon and a motor and provides load information.

[0016] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, wherein each of the plurality of tendon-routing disks includes a recess sized to receive a portion of an adjacent magnetic spherical joint.

[0017] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, wherein each of the plurality of magnetic spherical joints defines a diameter of 1 mm.

[0018] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, wherein the plurality of magnetic spherical joints are self-aligning.

[0019] In some aspects, the techniques described herein relate to a tendon-assisted magnetically steered robotic delivery device, wherein the plurality of tendon-routing disks and the plurality of magnetic spherical joints and in mechanical contact so that axial rigidity is maintained during use.

[0020] In some aspects, the techniques described herein relate to a robotic catheter including: a plurality of tendon-routing disks; and a plurality of magnetic spherical joints.

[0021] In some aspects, the techniques described herein relate to a robotic catheter, further including: further including a stem including tendon routing channels; four tendons coupled to the plurality of tendon-routing disks through the stem, the four tendons structured to actuate the robotic catheter; and two motors coupled to the four tendons and structured to actuate the tendons.

[0022] In some aspects, the techniques described herein relate to a system including: a robotic catheter including a plurality of tendon-routing disks, a plurality of magnetic spherical joints, a stem including tendon routing channels, four tendons coupled to the plurality of tendon-routing disks through the stem, the four tendons structured to actuate the robotic catheter, and two motors coupled to the four tendons and structured to actuate the tendons; and a magnetic field controller that generates a magnetic field to interact with the plurality of magnetic spherical joints to steer the robotic catheter.

[0023] This summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices or processes described herein will become apparent in the detailed description set forth herein, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements.BRIEF DESCRIPTION OF DRAWINGS

[0024] The device is explained in even greater detail in the following drawings. The drawings are merely exemplary and certain features may be used singularly or in combination with other features. The drawings are not necessarily drawn to scale.

[0025] FIG. 1 A is a perspective view of a cervix and its surrounding organs, according to some implementations.

[0026] FIG. IB is a perspective view of a curved tandem device and template placed at a vaginal opening, according to some implementations.

[0027] FIG. 1C is a perspective view of straight conventional needles with straight delivery devices having straight, parallel trajectories that fail to cover the entire tumor, according to some implementations.

[0028] FIG. ID is a perspective view of the same commercial needles used with a tendon-assisted magnetically steers (TAMS)robotic delivery device can be steered to reach a target position, according to some implementations.

[0029] FIG. 2A is a side view of a TAMS robot, according to some implementations.

[0030] FIG. 2B is a perspective view of a articulated tip design of the TAMS robot, according to some implementations.

[0031] FIG. 2C is a side view of the articulated tip of FIG. 2B showing the kinematics due to tendon actuation, according to some implementations.

[0032] FIG. 2D is a graph showing a kinematic model versus experimental data due to tendon actuation, according to some implementations.

[0033] FIG. 2E is a top view of a tendon pulling mechanism of the TAMS robot of FIG. 2A, according to some implementations.

[0034] FIG. 3 A is a graph showing a response of the closed loop control system to a step input, according to some implementations.

[0035] FIG. 3B is a graph showing a response of the system to a ramp input, according to some implementations.

[0036] FIG. 4 is a schematic representation of a robotic needle and delivery device system, according to some implementations. The delivery device, indicated by a red-dotted line is actuated by tendon forces indicated by fi, while the magnetic-actuation is modeled by a tip-force, F(p, 'ma, 'me) along the Y-axis (see box inset for global and local axes directions).

[0037] FIG. 5A is a graph showing robot shape at rest (blue cylinder) and under a total tendon tension of ~ 6 N (green cylinder), according to some implementations.

[0038] FIG. 5B is a graph showing robot shape at rest (blue cylinder, magnet distance ~ 430 mm) and the deformed shape as the magnet is brought closer to ~ 45 mm along the y-axis (green cylinder), according to some implementations.

[0039] FIG. 5C is a graph showing robot shape at rest (blue cylinder, magnet distance ~ 430 mm and total tendon tension 0 N) and as the magnet is brought closer and tendons are tensioned to ~ 6 N, according to some implementations. Red circles indicate marker (ground truth) positions for each case.

[0040] FIG. 6 is a graph showing robot shape at rest (blue cylinder, magnet distance ~ 430 mm and total tendon tension 0 N) and as the magnet is brought much closer (||p|| = 50 mm) and tendons are tensioned to ~ 6 N, according to some implementations. Red circles indicate ground truth under zero tendon tension, blue squares indicate marker (ground truth) positions for failure case, when the tendons are tensioned.

[0041] FIG. 7A is a perspective view of an experimental setup, according to some implementations.

[0042] FIG. 7B is a perspective view of a tendon pulling mechanism with antagonistic motion, according to some implementations.

[0043] FIG. 7C is a perspective view of a trial in phantom tissue with robotic arm, according to some implementations.

[0044] FIGS. 8A-E are a series of photographs showing progress of a needle being inserted for about 11mm, 36mm, 61mm, 86mm, and 111mm (respectively from left to right) into the gelatin block used as a tissue phantom, according to some implementations. The delivery device is actuated using both modalities (tendon and magnet) and the magnet is displaced by Staubli robotic arm. The trajectory taken by the needle is depicted by red dashed lines. In the last image on the right, trajectory of the needle without any steering actuation (shown by blue dotted line) is compared with the actual trajectory of the needle. Tip deflection is close to 20 mm.DETAILED DESCRIPTION

[0045] Following below are more detailed descriptions of concepts related to, and implementations of, methods, apparatuses, and systems for tendon-assisted magnetically steered robotic delivery devices. Before turning to the figures, which illustrate certain exemplary embodiments in detail, it should be understood that the present disclosure is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology used herein is for the purpose of description only and should not be regarded as limiting.

[0046] Interstitial brachytherapy requires up to 20 straight needles to be inserted to surround and irradiate deep-seated tumors, but may offer sub-optimal radiation dosage in cases of advanced cancers. This work introduces the design of a novel tendon-assisted magnetically steered (TAMS) robotic delivery device (e.g., a stylet, catheter, etc.) to steer commercially available brachytherapy needles. The dual-actuation modality (magnetic- and tendon-driven) allows for increased bending compliance while retaining axial rigidity at extremely small diameters (OD: 1.4 mm), key properties for steering hollow needles from within their lumen. We also develop a two-tube Cosserat rod model that predicts the behavior of the TAMS robot and needle assembly under actuation from tendons, external magnetic fields, and finally combined magnet+tendon forces. We validate our model in free space and demonstrate the capability of the TAMS robot and dualactuation modalities to steer brachytherapy needles to very high curvatures inside phantom tissue.

[0047] Cervical cancer is the fourth highest cause of cancer mortality in women, accounting for 342,000 deaths in 2020. Locally advanced cervical cancer (LACC) is an advanced form of cervical cancer where the tumorous lesion may have extended beyond the cervix to the pelvic sidewall or surrounding organs like the bladder or sigmoid colon (see FIG. 1A). As a result, the three yearsurvival rate of advanced cervical cancer remains as low as 43-54% . External beam radiation therapy followed by high dose rate (HDR) intracavity (IC) or interstitial (IS) brachytherapy (BT) is the current standard of care in LACC cases. IC / IS brachytherapy involves the placement of a radioactive source within, or adjacent to a tumor via applicators like a tandem device (see FIG. IB). A tandem is a tube, approximately 6 mm in diameter, inserted from the vaginal opening into the uterine canal, which may be curved to match the uterine curvature (see FIG. IB). Next, between 15-20 additional interstitial needles are inserted through the perineum via a perforated template (see FIGS. 1B-C). Straight needles, that are currently used in ISBT, result in parallel needle paths when inserted through these perforated templates. This may result in suboptimal radiation coverage of the tumor (see FIG. IC). Unexpected needle displacement towards the tailbone is often observed to be as high as 14-20 mm. In patients with more advanced tumors, such as those extending into the iliac artery or sigmoid colon, inserting straight rigid needles prone to movement can be dangerous (see FIG. IC). While surgical planning can be used to optimize robotic rigid needle placement, this approach applies to cancers where the tumors are still limited to linear needle paths (for example, prostate cancer). The curvature of the uterus cannot be accounted for by straight needles, for which, 3D printed custom curved needles or templates have been suggested. However, unexpected uterine displacement due to bladder filling may be as significant as 91 degrees, and pre-curved needles cannot adapt to such extreme displacement. In recent years, a variety of steerable needle designs have been studied, including concentric tubes, passive and active bevel-tip, tendon-actuated, and magnetically actuated needles. However, these designs are suitable when there is only one needle required for a procedure. Considering the large number of needles required in ISBT procedures, it is not practical to use steerable needles. Instead, it is more practical to design a steerable delivery device and use that to guide a multiplicity of commercially available ISBT needles to desired target locations (see FIG. ID).

[0048] In some implementations, the TAMS robotic delivery device is used in cardiac procedures. In some implementations, the TAMS robotic delivery device delivers a laser, a heart source, a cutter, medication, etc. from the outside to the inside and is steerable. In some implementations, the TAMS robotic delivery device can cut through tissue while being steered. In some implementations, the TAMS robotic delivery device is used for cardiac ablation, deep brain stimulation, etc.

[0049] Minimizing tissue damage is a major challenge in steerable needle design. To overcome this issue, the designed needle must have several characteristics including lower needle stiffness in non-axial directions and rotation-free steering capability. These considerations rule out a few design paradigms including concentric tube (due to high rigidity in bending directions), unidirectional bevel tip, and screw-tip (due to the necessity of needle rotation for steering in different trajectories) designs. Some have proposed a tendon-actuated needle that overcomes this issue and shows great targeting accuracy and precision. In a different approach for tackling this challenge, a magnetically actuated needle for neurosurgical procedures has been suggested. Additionally, a creative bio-inspired programmable bevel -tip needle has been developed that takes care of the aforementioned issue. When there is only one needle (or two needles maximum) is required for our application, these designs are totally suitable, but considering the large number of needles in our case, it is not cost effective to use such modalities.

[0050] To address this drawback, continuum robot delivery devices were suggested. To the best of our knowledge, the tendon-actuated robotic delivery devices have been designed by micromachining joints into super elastic metal tubes. Considering the tendon actuated delivery device proposed, the delivery device lacks sufficient axial rigidity while a high force is being exerted. To compensate for the loss of axial rigidity, these designs need to be reinforced with metal rods through their central axis. In this work, by introducing magnetic spherical joints inspired by the magnetic ball-chain design, our robot is not only automatically rigid in the axial direction, but sufficiently compliant in the bending direction. Furthermore, Since the spherical joints are also magnetic, we can enhance the steerability of the robot with an external magnetic field in addition to tendon actuation. This approach has been taken before in another study. However, in this previous study, magnetic actuation modality is not utilized, and it is difficult to miniaturize the model proposed to fit into a 15 gauge needle with inner lumen diameter of 1.4 to 1.5 mm. High miniaturization ability is the key advantage of our proposed design, and to the best of our knowledge, the smallest robot in the world, that is both tendon-driven and magnetically actuated.

[0051] The remainder of this paper is organized as follows: We first summarize the mechanical designs in Section II for the TAMS delivery device. We elaborate on the front-end design with delivery device and needle (Section II- A) and the back-end design with tendon-actuation, external magnet for generating the magnetic field for actuating the delivery device magnetically, and the position capturing device that we used (Section II-B). We continue in Section III by providing amechanical model for the tendon actuation (III- A) and magnetic actuation (IIIB), and a proposed numerical solution (III-C). Then in Section IV, we show several trials both in the free open space (IV-A) and the phantom tissue (IV-B). Ultimately, we wrap up this paper by representing our conclusions in Section V.

[0052] II. ROBOT DESIGN

[0053] A. Front-end Design

[0054] To achieve bending compliance for our robot, we implemented a tendon actuated magnetic spherical joint at the robot’s tip for steering inside the tissue. This is illustrated in FIG. 2B, where you can see that we designed the robot’s tip to have 2 degrees of freedom for bending. Four tendons have been considered to actuate the tip to bend in two independent planes. In addition to ensuring bending flexibility, we also needed the robot to maintain axial rigidity. This is crucial when it is actuated with tendons or inserted into tissues to prevent any unwanted compression. Because of the limitation on applying force to the tendons and also limited size of the needle, the tendon actuating would not generate enough bending moment. We can utilize an external magnet to apply force to the spherical magnets at the robot’s tip, thereby enhancing its bending compliance. To fulfill these requirements, we opted for a tendon actuated magnetic spherical joint design.

[0055] To control the bending direction of the tip, we required a total of 4 tendons, so we designed 4 holes through the cylindrical parts to route these tendons. We had to ensure that the outer diameter of these cylindrical parts remained below 1.4 mm, as this corresponds to the inner diameter of the needles commonly used in surgical procedures. Our choice of nitinol tendons had a diameter of 0.1 mm, so we designed the routing holes with a slightly larger diameter of 0.16 mm to ensure a proper fit. Routing holes with diameter less than 0.16 mm will increase friction to the bending mechanism and reduce the bending compliance. In some implementations, other materials are used. Nitinol is not the only material that is suitable for use in tendons described herein.

[0056] The front-end of the robot consists of two components: a proximal micromachined nickeltitanium (nitinol) stem with tendon-routing channels, and a distal tip equipped with a TAMS robotic joint (see FIG. 2B). In some implementations, the stem is constructed of other materials. Nitinol is not the only material that is suitable for use in front-end components, in someimplementations, the stem is a nitinol tube with an ID of 1.07 mm and an OD of 1.35 mm. In some implementations, the choice of nitinol for the tube material is particularly significant because it is superelastic and non-magnetic. This unique property allows us to effectively steer the robot within tissue with follow-leader motion when the robot is inserted into the tissue. The stock nitinol tube was micromachined with a femtosecond laser (Optec WS-Flex, Institute for Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta), so that the stem could interface with the TAMS joint at the distal tip. This tendon-assisted magnetically steered (TAMS) joint at the robot’s tip comprises of two components: 1) tendon-routing disks and 2) magnetic spherical joints, illustrated in FIGS. 2B-C. The cylindrical tendon routing disks are interlaced between the magnetic spherical joints, allowing for two degree-of-freedom (2 -DoF) motion between any two consecutive disks. To achieve this 2-DoF bending in the overall joint, four routing holes have been incorporated into the cylindrical disks for routing four tendons. This is redundant, given that only three tendons would ideally suffice for 2-DoF control; however, adding another tendon does not result in any diameter savings, while having four tendons makes the control problem simpler. We had to ensure that the outer diameter of these cylindrical disks remained below 1.4 mm, as this corresponds to the inner diameter of the 15-gauge needles commonly used in ISBT procedures. For the fabrication of the cylindrical disks, we used the Boston Micro Fabrication microArch S 140 3D printer (Institute for Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta). This printer utilizes photosensitive resin as its printing material and has an optical resolution of 10 pm. Our choice of nitinol tendons had a diameter of 0.1 mm, so we designed the routing holes with a slightly larger diameter of 0.16 mm to ensure a proper fit and reduce friction artefacts. Furthermore, we incorporated a central aperture within the routing disks. This aperture allows the spherical magnets to partially sink into the cylinder disks, increasing the joint’s stability and more effective functioning as universal ball-joints. Since the diameter of the magnetic spheres was 1 mm, we designed the central aperture to be slightly smaller, at 0.6 mm. Note that spherical magnets will self-align. This will serve to increase stability in the TAMS joint and help the magnets retain in their positions within the disks. This design will also maintain axial rigidity, since the lack of any gaps between the magnetic disks and spherical joints make the robot tip inherently rigid, i.e., bending compliance is achieved with spherical joints and not by removing material in the form of notch-joints.

[0057] Considering pure tendon-actuation, FIGS. 2A-C show consecutive disks, with the angle between them due to tendon actuation indicated by 9. This is a purely geometric value, and is afunction of tendon stroke. The total angle for n such spherical joints is given by ©total is given as follows:Where Al is the stroke of the tendon pulling motor, n is distance from routing tendon to the center and n is the number of ball joints. In this work, we choose n = 20. The total length of the tip is 37 mm. FIG. 2D displays the values of ©total calculated using Eq. (1) in comparison to the collected experimental data. The discrepancy between the two arises from the fact that the kinematic model proposed in Eq. (1) does not account for tendon elongation due to friction losses or needle stiffness (when the TAMS delivery device is inserted into the needle). Consequently, encoder data cannot be utilized to accurately determine the bending angle. In Section III, we introduce a quasi-static model that relates the bending angle to tensile forces. This approach provides a more comprehensive framework for modeling the robot.

[0058] Furthermore, while tendon-actuation allows for dexterous motion of the TAMS delivery device in free-space, placing an ISBT needle over the delivery device drastically reduces the robot’s dexterity. This reduced robot dexterity is due to the high stiffness of the needle surrounding the delivery device. To overcome this stiffness, our novel design also utilizes an external magnet to apply an additional force to the spherical magnets at the robot’s tip, thereby increasing its bending compliance. More on the effects of this magnetic action will be discussed in Section III.

[0059] In addition to the 4 tendon holes in the cylindrical parts, we incorporated a central aperture. This aperture allows the spherical magnets to partially sink into the cylinder, enhancing the robot’s stability and effectively functioning as ball joints. Since the diameter of the magnetic spheres was 1 mm, we designed the central aperture to be 0.6 mm.

[0060] For the fabrication of the cylindrical disks, we employed the Boston Micro Fabrication microArch S140 3D printer. This printer utilizes photosensitive resin as its printing material and boasts an optical resolution of 10 micrometers.

[0061] The magnetic spherical joint mechanism is positioned on top of the nitinol tube, which has an ID of 1.07 mm and an OD of 1.35 mm. The choice of nitinol for the tube material is particularly significant because it is super elastic. This unique property allows us to effectively steer the robot within tissue and employ a follow-leader motion when the robot is inserted into the tissue.

[0062] B. Back-end Design

[0063] To operate the 4 tendons, as discussed in the previous section, we require 4 motors that are connected to lead screws, enabling them to generate linear motion for pulling the tendons. However, due to the symmetrical design of the bending mechanism and the antagonistic movement of two pairs of tendons, it is possible to reduce the number of actuators (<]>8 mm, Maxon Metal Brushes, 0.5 Watt) to just 2. In FIG. 2E, we provide an illustration of one of these tendon-pulling mechanisms, which is responsible for actuating two opposing tendons. Attached to the lead screw is a load cell (MDB-5 51b capacity, Transducer Techniques). The motor allows the load cell to either pull the tendon or let it relax. The lead screw nut is also linked to another 3D printed part via a Kevlar string. The second load-cell which is attached to this 3D printed part, also connected to a second tendon, causing the tip to bend within the same plane but in the opposite direction.

[0064] To maintain tension on the Kevlar string at all times, eight springs (4.57 mm OD, spring rate 0.525N / mm, Lee Spring) are employed. When the motors attempt to relax the kevlar string, these springs exert force on the other side of the kevlar string, pushing it in the opposite direction to counteract the motor’s movement. Springs can exert force up to 17.4 Newton which is sufficient for this work.

[0065] APID controller for tendon actuation mechanism has been selected to control the tensile force in the tendons. FIG. 3 A displays the step response of the system, while FIG. 3B demonstrates the system’s response to an input employed in experiments. As observed in FIG. 3B, upon applying approximately 4.8 newtons of force, the tendons enter the super elastic region. Applying more force beyond this threshold will result in plastic deformation of the tendons.

[0066] As illustrated in FIG. 2A, the proximal end and tendon pulling mechanism are positioned on top of a linear insertion mechanism. This setup employs a DC motor (Micro Metal Gear motor 12V, Pololu) to drive a lead screw, thereby generating insertion and retraction movements. To ensure precise linear motion, two stainless steel rods measuring 10 mm in diameter are inserted into linear ball bearings within the mechanism.

[0067] III. MECHANICAL MODEL

[0068] In this section, we will introduce a modified two-tube Cosserat rod model for the robotic delivery device and needle shape estimation, first under tendon-tension, then through magneticactuation, and finally using the dual tendon-force and magnetic-actuation modalities. This will lead to a kinematic model that relates tendon stroke to tip displacement, including tendon elongation under tension (which becomes dominant for needle steering).

[0069] In some implementations, as shown in FIGS. 2A-2E, a control system 100 (e.g., for brachytherapy) includes a tendon-assisted magnetically steered robotic delivery device 104 and a magnetic actuator 108. The tendon-assisted magnetically steered robotic delivery device 104 includes a stem 112 including tendon routing channels, and a distal tip 116 coupled to the stem 112 and including a plurality of tendon-routing disks 120, and a plurality of magnetic spherical joints 124. Four tendons 128 are coupled to the distal tip 116 and structured to actuate the distal tip 116 with two degrees of freedom. A tendon pulling mechanism 132 is coupled to each of the four tendons 128 to actuate the tendons 128. The magnetic actuator 108 includes a magnet 136 (e.g., a permanent magnet, a magnetic field generator, etc.) and a robotic arm 140 that is structured to move the magnet 136. The magnet 136 is structured to magnetically couple with the magnetic spherical joints 124 of the distal tip 116. The control system 100 also includes one or more processing circuits 144 including one or more memory devices coupled to one or more processors, the one or more memory devices configured to store instructions thereon that, when executed by the one or more processors, cause the one or more processors to: control operation of the magnetic actuator 108 and the tendon pulling mechanism 132 to control operation of the distal tip 116 of the tendon-assisted magnetically steered robotic delivery device 104. The control system 100 further includes a linear advance assembly 148 including a motor 152 controlled by the one or more processing circuits 144 and a linear actuator 156 (e.g., linear bearings, ball screw actuator, etc.). In some implementations, the linear advance assembly 148 aids in advancing the control system 100 during an operation. The one or more processing circuits 144 is structured to coordinate actions of the tendon-assisted magnetically steered robotic delivery device 104, the magnetic actuator 108, the tendon pulling mechanism 132, and the linear advance assembly 148.

[0070] In some implementations, the tendon pulling mechanism 132 includes a motor 160 that is controlled by the one or more processing circuits 144. The motor 160 controls movement of a first load cell 164 that is connected to a second load cell 168 by a string 172 via a pulley wheel 176. A first tendon 180 is connected to the first load cell 164 and a second tendon 184 is connected to the second load cell 168. A spring 188 biases the second load cell 168 away from the first load cell 164.

[0071] In operation, the one or more processing circuits 144 controls the motor 160 to move the first load cell 164 and therefore the first tendon 180. The second load cell 168 is connected to the first load cell 164 via the string 172 and therefore the movement of the second load cell 168 corresponds to the movement of the first load cell 164 and produces and coordinated movement of the distal tip 116 of the tendon-assisted magnetically steered robotic delivery device 104. The magnetic actuator 108 is positioned to interact with the plurality of magnetic spherical joints 124 such that a shape of the distal tip 116 can be manipulated within a body of a patient. Dynamic shapes can be accomplished using the control system 100. For example, atypical, earthworm-type shapes are possible and the distal tip 116 can be dynamically guided during placement.

[0072] A. Static Model

[0073] Figure 4 shows a simplified schematic of the robotic delivery device and needle assembly, the frames associated with each body and the forces applied on the robotic delivery device. As described in the previous sections, the robotic delivery device is inserted within a 15 gauge ISBT needle and steers the needle from within. Therefore, the two bodies, i.e. the needle and the delivery device run coaxially, sharing a common center line, indicated by pc(s) in FIG. 4. However, since the delivery device is not rigidly fixed to the needle, it is free to twist about the tangent to this centerline independently. We assume that the material frame orientation is a function of arc length s, with the z axis along the centerline tangent and x-y axes along the material cross-section (see FIG. 4). The spatial evolution of the common centerline and material frame orientation is given as follows:The material frame orientation of the delivery device is indicated by Ri(s) and that of the needle is indicated by R2(s). Henceforth, the subscripts, i = { 1, 2}, will be used for delivery device and needle respectively. Furthermore, vi(s) E R3is the linear strain rate and ui(s) E R3is the angular strain rate. Due to the coaxially aligned nature of the assembly, the two tubes have equal bending curvatures and cross-sectional shear strains, i.e. ui|x,y and vi|x,y. However, twist rate i.e. ui|z is considered separately for each individual tube, and elongation strain rate is neglected in this work, i.e. vi|z= 0. The relative twist angle between the two tubes is given by a(s) (see FIG. 4) and is defined by the relationship, d(s) = U2,z(s) - ui,z(s), relating the twist strain rates of the two Cosserat rods. Considering the cross-sectional equivalence and the relative twist rate relationship, the angular strain vectors between the two Cosserat rods are related to each other as follows:u2(s) = + d(s)e3(3)Finally, for any two vectors a, b E R3, the dot notation a = da / ds will represent a spatial derivative, and [a]b will represent the skew-symmetric matrix corresponding to the cross-product operation, a x b. In this work, both the delivery device and the needle are modeled as special Cosserat rods with internal forces and moments, m E R3and mi E R3respectively. Applied forces and moments on rod i = { 1, 2}are indicated by fi E R3and Ti E R3respectively. The static equilibrium for the combination of the k Cosserat rods is additive in the x-y plane of the material frames while it is individually considered for forces and moments about the z-axis of the material orientation frame. The x-y-components of the combined equilibrium equations for a set of k tubes are given as follows:and the sum of the forces in the local material frames is as follows:where Rz(ai) = 13 3, and for the two tube case Rz(a2) = Rz(a). The z-component of the static equilibrium equation is individually considered for each tube, and is given as follows:For each rod, i.e., the needle and the delivery device, the applied moment-curvature relationship is given as follows:Here, it- is the pre-curvatureis the initial strain rate in the tube in the absence of any external forces. In this work, Ei = 45 GPa is the elastic modulus and ui = 0.33 is the Poisson’s ratio for the nitinol delivery device. The elastic modulus for the plastic needle, E2 = 9.155 GPa is derived from cantilever beam experiments, and 02 = 0.5 is standard for plastics. Finally, in the absence of any external forces or magnetic fields, tensioning the tendons is the only source of bending in the delivery device. The tendon position is expressed as a function of arc-length in thelocal body-frame of the delivery device as, pj = [x y 0]T, where j = { 1, . . . , 4}, is the tendon number. This force is given, as follows:Here, Xj is the scalar tension in tendon j, which, as described earlier, is a measurable quantity. Furthermore, fzj = T2j = 0, since the needle is passive and does not contain any tendons. The derivatives of the tendon body-frame location vector are defined for each tendon:Knowing pj , since tendon routing fixed and known and from Eqs. (12) in Eq. (10), we can express tendon forces purely in terms of ui, vi and their derivatives. Plugging this and the momentcurvature relationship in Eq. (7) in our equilibrium equations (Eqs. (4)-(6)), we can simply express the final differential equation as an A^, v1, u2,z\T= b form, where A is a matrix in terms of known quantities (such as pj ) and state variables: ui, vi, U2,z.

[0074] B. Magnetic Field Estimation

[0075] In the presence of the external magnet, an external force is applied on the spherical magnets located at the tip of the delivery device. These spherical magnets are modeled by a single point dipole at the tip of the robot with its dipole moment mcwhich is a vector from south pole to north pole with unknown magnitude. Also, we modeled the external magnet, by a point dipole at the center of the magnetic disk with its dipole ma. The magnetic force applied to the end robot’s tip is given bywhere p = pc-pais vector from center of external magnet to the tip of robot, po = 47t* 10-7N. A2is the permeability constant, Z = I - 5ppT

[0030] ,

[0076] Since the magnetic chain at the tip has been modeled with a single dipole point, the magnitude of mc is unknown. Castigliano’s theorem has been used for this purpose. The needle is modeled as a curved beam, and an out-of-plane force is applied to the tip. Since Bending and torsion strain are dominant and axial and transverse strain are negligible deflection in the direction of the applying force is given bywhere M is bending moment and T is torsion torque. M and T are function of s. Having 5y, we can solve the Eq. (14) and find the f and me from Eq. (13). mccan be assumed constant since the magnet at the robot’s tip are permanent magnets.

[0077] C. Numerical Solution

[0078] The inputs to the equilibrium conditions, expressed in the simplified A [ii^ U2IZ]T= b form, are the tendon-tensions, j, applied at the base of the robotic delivery device. An unknown in our model is, a(0), the relative twist angle at the base of the robot. In other words, we do not know the orientation of the tendons at the base of the robotic delivery device, since the delivery device is within the needle. Assembling and locking the needle on the delivery device requires both tubes to be twisted by an arbitrary and unknown amount, resulting in uncertainty in a(0). The boundary conditions at the tip of the needle, i.e. s = L, are given as follows:A shooting method is used to find the solutions for the state variables, s = 0, that satisfy the boundary conditions at the tip s = L. Another optimization runs on top of the shooting method, to find a value for the initial twist angle, a(0), that minimizes position error between the centerline, p(s) and a known ground truth value from infrared markers on the needle (described in the next section).

[0079] IV. EXPERIMENTS AND RESULTS

[0080] A. Free space trials

[0081] The preliminary model proposed in the previous section (see Section III) is a free-space model, i.e., it does not consider external forces from tissue. While this is a limitation of the current model, it is necessary to properly characterize the TAMS robot in free space before we consider its behavior in tissue. Therefore, to validate this mechanical model, we conducted three trials in free space: 1) only tendon-actuation with no external magnet influence, 2) magnetic actuation with zero tendon-tension, 3) dual-actuation with tendon-tension and magnetic tip forces. The experimental setup for the tests is shown in FIG. 7. Seven infrared markers were placed on astandard 15 gauge ISBT plastic needle at arc-lengths s = {4.43, 46.73, 115.2, 153.21, 188.43, 209.87, 229.62} mm and were tracked by four Vero v2.2 motion tracking cameras (Vicon Motion Systems Ltd., United Kingdom). An additional set of five markers were placed at the base of the robot to determine a global frame for the entire system. Four markers along the diameter of the magnet track the pose of the external magnet and its distance from the central axis of the needle. This allows us to ensure that the plane of the magnet remains parallel to the needle axis, and the tip of the robot is aligned with the center of the magnet (see FIG. 7A). FIGS. 5A-C indicate the shape of the needle for the three actuation strategies tested in free space. Note that the shape of the TAMS robot and needle assembly is not straight at rest, however, our model can account for that using nonzero values for u^x y, which are manually tuned to match the shape of the robot at rest. This is a significant advantage of our modeling approach over previous work, which assumes a straight needle at rest, which is practically unlikely to occur in an OR room setting.

[0082] Failure Case: When the magnet is brought significantly close to the needle tip, we find that the model under-performs and fails to predict the needle tip location successfully. This is highlighted in FIG. 6, where the magnet was brought extremely close to the needle tip (i.e., Ilpll = 50 mm). The model is correctly able to predict the shape of the robot with a tip position error of 2.62 mm, under zero tendon tension. However, as tendon tension increases to its maximum value of 6 N, tip error increases to 10.47 mm. As indicated by the blue squares depicting the ground truth centerline positions for this case, the model predicts a much lower curvature under tendon tension and magnetic actuation, when the magnet is close. The observed deformation of the TAMS delivery device and needle is much higher, under these input conditions. The reason for this high tip error, is due to the magnetic tip force increasing significantly as the tendon is tensioned further. Our model assumes that the distance between the magnet plane and the needle axis remains constant when the tendon is tensioned. This assumption holds, when the external magnet is significantly far away from the source (since tendon tension only slightly deforms the robot in comparison to magnetic forces). Since, for small values of Ilpll, the magnet force on the TAMS delivery device tip, f(p, ma, mcincreases asymptotically, our assumption fails for magnets brought very close to the needle.

[0083] B. Trials in Phantom Tissue

[0084] After testing in free space, we experimented with the TAMS robot inside phantom tissue to observe its behavior under tissue forces on the needle. In this experiment, we aimed to bendthe needle in the positive Y-direction (global frame in FIG. 4) within the phantom tissue. To achieve this, we used a robotic arm (Staubli, Switzerland) to ensure the external magnet remained aligned with the TAMS robot’s tip (see FIG. 7C), controlled manually using jogging mode. The phantom tissue was made using unflavored Gelatin, with stiffness achieved by changing the gelatin concentration in water. In this work, we used a ratio of 15 grams per cup of water. The gelatin was first dissolved in room temperature water and then stirred into boiling hot water to prevent clumping. Subsequently, it was refrigerated for eight hours. The insertion of the needle into the gelatin was facilitated by an integrated insertion mechanism within the TAMS Robot, enabling a gradual advancement of the needle. We collected top-view images throughout the experiment to document the needle’s behavior. FIGS. 8A-E present a series of frames extracted from these images, visually illustrating the needle’s bending toward the positive Y-direction. Of note, unlike previous work, steering within the phantom did not significantly reduce the steering capabilities of the needle.

[0085] V. CONCLUSIONS

[0086] In this work, we have developed a novel design for a robotic delivery device to steer interstitial brachytherapy (ISBT) needles in the treatment of locally advanced cervical cancer. A new dual -actuation strategy was proposed to steer the robotic delivery device, which combined tendon-actuation with magnetic-steering (TAMS). A two coaxial-tube Cosserat rod model was used, that was based upon our previous work, to model the quasi-static behavior of the robot under 1) tendon actuation only, 2) magnetic forces, 3) dual TAMS actuation. We found that in firee- space, the model was capable of estimating the robot shape very closely with a mean tip position error of only 1.51 mm under dual-actuation. We also demonstrated a failure case, where the model predicted shape deviated from observed shape when the magnet was brought extremely close to the delivery device (tip errors > 10 mm). Finally, phantom tissue experiments with the external magnet controlled by a 6-DoF robotic arm demonstrated that deflection within tissue was equivalent to that in free-space. We hypothesize that this is due to unequal forces on either side of the needle pushing it further in the direction of its actuated curvature (and the direction of the magnet). In our future work, we will further expand upon the model introduced in this work for predicting shape in the presence of tissue interaction forces. Furthermore, a control strategy including this model will be developed to steer the TAMS-delivery device and needle assembly in tissue while avoiding obstacles.

[0087] For purposes of this description, certain advantages and novel features of the aspects and configurations of this disclosure are described herein. The described methods, systems, and apparatus should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed aspects, alone and in various combinations and sub-combinations with one another. The disclosed methods, systems, and apparatus are not limited to any specific aspect, feature, or combination thereof, nor do the disclosed methods, systems, and apparatus require that any one or more specific advantages be present or problems be solved.

[0088] Although the figures and description may illustrate a specific order of method steps, the order of such steps may differ from what is depicted and described, unless specified differently above. Also, two or more steps may be performed concurrently or with partial concurrence, unless specified differently above. Such variation may depend, for example, on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations of the described methods could be accomplished with standard programming techniques with rule-based logic and other logic to accomplish the various connection steps, processing steps, comparison steps, and decision steps.

[0089] Features disclosed in this specification (including any accompanying claims, abstract, and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The claimed features extend to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract, and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0090] As used in the specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about”, it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. The terms “about” and “approximately” are defined as being “close to” as understood by one of ordinary skill in the art. In one non-limitingaspect the terms are defined to be within 10%. In another non-limiting aspect, the terms are defined to be within 5%. In still another non-limiting aspect, the terms are defined to be within 1%.

[0091] The terms “coupled”, “connected”, and the like as used herein mean the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another. If “coupled” or variations thereof are modified by an additional term (e.g., directly coupled), the generic definition of “coupled” provided above is modified by the plain language meaning of the additional term (e.g., “directly coupled” means the joining of two members without any separate intervening member), resulting in a narrower definition than the generic definition of “coupled” provided above. Such coupling may be mechanical, electrical, or fluidic. For example, circuit A communicably “coupled” to circuit B may signify that the circuit A communicates directly with circuit B (i.e., no intermediary) or communicates indirectly with circuit B (e.g., through one or more intermediaries).

[0092] Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, “left”, “lower”, and “upper” designate direction in the drawings to which reference is made. The words “inner” and “outer” refer to directions toward and away from, respectively, the geometric center of the described feature or device. The words “distal” and “proximal” refer to directions taken in context of the item described and, with regard to the instruments herein described, are typically based on the perspective of the practitioner using such instrument, with “proximal” indicating a position closer to the practitioner and “distal” indicating a position further from the practitioner. The terminology includes the above-listed words, derivatives thereof, and words of similar import.

[0093] Throughout the description and claims of this specification, the word “comprise” and variations of the word, such as “comprising” and “comprises”, means “including but not limited to”, and is not intended to exclude, for example, other additives, components, integers or steps. “Exemplary” means “an example of’ and is not intended to convey an indication of a preferred or ideal aspect. “Such as” is not used in a restrictive sense, but for explanatory purposes.

[0094] The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention.

[0095] EXAMPLES

[0096] Example 1. A tendon-assisted magnetically steered robotic delivery device comprising: a stem including tendon routing channels; and a distal tip including a plurality of tendon-routing disks, and a plurality of magnetic spherical joints.

[0097] Example 2. The tendon-assisted magnetically steered robotic delivery device of example 1, wherein the stem is formed of ni tinol.

[0098] Example 3. The tendon-assisted magnetically steered robotic delivery device of example 1, wherein the stem defines an internal diameter of more than 1 mm and an outside diameter of less than 1.4 mm.

[0099] Example 4. The tendon-assisted magnetically steered robotic delivery device of example 1, wherein the stem is formed of a non-magnetic material.

[0100] Example 5. The tendon-assisted magnetically steered robotic delivery device of example 1, wherein each of the plurality of tendon-routing disks are positioned between two of the plurality of magnetic spherical joints.

[0101] Example 6. The tendon-assisted magnetically steered robotic delivery device of example 5, wherein the distal tip defines two degrees-of-freedom between any two adjacent tendon-routing disks.

[0102] Example 7. The tendon-assisted magnetically steered robotic delivery device of example 1, further comprising three tendons coupled to the distal tip through the stem, the three tendons structured to actuate the distal tip.

[0103] Example 8. The tendon-assisted magnetically steered robotic delivery device of example 7, wherein each of the plurality of tendon-routing disks includes three routing holes, each of the routing holes structured to receive one of the three tendons.

[0104] Example 9. The tendon-assisted magnetically steered robotic delivery device of example 7, further comprising a fourth tendon coupled to the distal tip through the stem, the fourth tendon structured to actuate the distal tip.

[0105] Example 10. The tendon-assisted magnetically steered robotic delivery device of example 9, wherein each of the plurality of tendon-routing disks includes a fourth routing hole, each of the fourth routing holes structured to receive the fourth tendon.

[0106] Example 11. The tendon-assisted magnetically steered robotic delivery device of example 9, further comprising two motors coupled to the four tendons and structured to actuate the tendons.

[0107] Example 12. The tendon-assisted magnetically steered robotic delivery device of example 9, further comprising four motors coupled to the four tendons and structured to actuate the tendons.

[0108] Example 13. The tendon-assisted magnetically steered robotic delivery device of example 12, further comprising four load cells, wherein each load cell is coupled between a tendon and a motor and provides load information.

[0109] Example 14. The tendon-assisted magnetically steered robotic delivery device of example 1, wherein each of the plurality of tendon-routing disks includes a recess sized to receive a portion of an adjacent magnetic spherical joint.

[0110] Example 15. The tendon-assisted magnetically steered robotic delivery device of example 1, wherein each of the plurality of magnetic spherical joints defines a diameter of 1 mm.

[0111] Example 16. The tendon-assisted magnetically steered robotic delivery device of example 1, wherein the plurality of magnetic spherical joints are self-aligning.

[0112] Example 17. The tendon-assisted magnetically steered robotic delivery device of example 1, wherein the plurality of tendon-routing disks and the plurality of magnetic spherical joints and in mechanical contact so that axial rigidity is maintained during use.

[0113] Example 18. Acontrol system for brachytherapy, the control system comprising: atendon- assisted magnetically steered robotic delivery device including: a stem including tendon routing channels; and a distal tip coupled to the stem and including a plurality of tendon-routing disks, and a plurality of magnetic spherical joints; four tendons coupled to the distal tip and structured to actuate the distal tip with two degrees of freedom; a tendon pulling mechanism coupled to each of the four tendons to actuate the tendons; a magnetic actuator including a permanent magnet and a robotic arm, the robotic arm structured to move the permanent magnet, and the permanent magnet structured to magnetically couple with the magnetic spherical joints of the distal tip; and one or more processing circuits comprising one or more memory devices coupled to one or more processors, the one or more memory devices configured to store instructions thereon that, when executed by the one or more processors, cause the one or more processors to: control operation of the magnetic actuator and the tendon pulling mechanism to control operation of the distal tip of the tendon-assisted magnetically steered robotic delivery device.

[0114] Example 19. The control system of example 18, wherein the tendon pulling mechanism includes four motors, each coupled to one of the four tendons.

[0115] Clause 20. A method of controlling a tendon-assisted magnetically steered robotic delivery device, the method comprising: inserting a distal tip of the tendon-assisted magnetically steered robotic delivery device; manipulating tendons to actuate tendon-routing disks coupled together via magnetic spherical joints to steer the distal tip in two degrees-of-freedom; and magnetically engaging the magnetic spherical joints with an external permanent magnet to assist in steering the distal tip.

Claims

What is claimed is:

1. A tendon-assisted magnetically steered robotic delivery device comprising: a distal tip including a plurality of tendon-routing disks, and a plurality of magnetic spherical joints, each of the plurality of magnetic spherical joints positioned between two of the plurality of tendon-routing disks.

2. The tendon-assisted magnetically steered robotic delivery device of claim 1, further comprising a stem including tendon routing channels, wherein the stem is formed of nitinol.

3. The tendon-assisted magnetically steered robotic delivery device of claim 1, further comprising a stem including tendon routing channels, wherein the stem defines an internal diameter of more than 1 mm and an outside diameter of less than 1.4 mm.

4. The tendon-assisted magnetically steered robotic delivery device of claim 1, further comprising a stem including tendon routing channels, wherein the stem is formed of a nonmagnetic material.

5. The tendon-assisted magnetically steered robotic delivery device of claim 1, wherein each of the plurality of tendon-routing disks are positioned between two of the plurality of magnetic spherical joints.

6. The tendon-assisted magnetically steered robotic delivery device of claim 5, wherein the distal tip defines two degrees-of-freedom between any two adjacent tendon-routing disks.

7. The tendon-assisted magnetically steered robotic delivery device of claim 1, further comprising: further comprising a stem including tendon routing channels; and three tendons coupled to the distal tip through the stem, the three tendons structured to actuate the distal tip.

8. The tendon-assisted magnetically steered robotic delivery device of claim 7, wherein each of the plurality of tendon-routing disks includes three routing holes, each of the routing holes structured to receive one of the three tendons.

9. The tendon-assisted magnetically steered robotic delivery device of claim 7, further comprising a fourth tendon coupled to the distal tip through the stem, the fourth tendon structured to actuate the distal tip.

10. The tendon-assisted magnetically steered robotic delivery device of claim 9, wherein each of the plurality of tendon-routing disks includes a fourth routing hole, each of the fourth routing holes structured to receive the fourth tendon.

11. The tendon-assisted magnetically steered robotic delivery device of claim 9, further comprising two motors coupled to the four tendons and structured to actuate the tendons.

12. The tendon-assisted magnetically steered robotic delivery device of claim 9, further comprising four motors coupled to the four tendons and structured to actuate the tendons.

13. The tendon-assisted magnetically steered robotic delivery device of claim 12, further comprising four load cells, wherein each load cell is coupled between a tendon and a motor and provides load information.

14. The tendon-assisted magnetically steered robotic delivery device of claim 1, wherein each of the plurality of tendon-routing disks includes a recess sized to receive a portion of an adjacent magnetic spherical joint.

15. The tendon-assisted magnetically steered robotic delivery device of claim 1, wherein each of the plurality of magnetic spherical joints defines a diameter of 1 mm.

16. The tendon-assisted magnetically steered robotic delivery device of claim 1, wherein the plurality of magnetic spherical joints are self-aligning.

17. The tendon-assisted magnetically steered robotic delivery device of claim 1, wherein the plurality of tendon-routing disks and the plurality of magnetic spherical joints and in mechanical contact so that axial rigidity is maintained during use.

18. A robotic catheter comprising: a plurality of tendon-routing disks; and a plurality of magnetic spherical joints.

19. The robotic catheter of claim 18, further comprising: further comprising a stem including tendon routing channels; four tendons coupled to the plurality of tendon-routing disks through the stem, the four tendons structured to actuate the robotic catheter; and two motors coupled to the four tendons and structured to actuate the tendons.

20. A system comprising: a robotic catheter including a plurality of tendon-routing disks, a plurality of magnetic spherical joints, a stem including tendon routing channels, four tendons coupled to the plurality of tendon-routing disks through the stem, the four tendons structured to actuate the robotic catheter, and two motors coupled to the four tendons and structured to actuate the tendons; and a magnetic field controller that generates a magnetic field to interact with the plurality of magnetic spherical joints to steer the robotic catheter.

Images