Patent Application
20120265051
The present teachings relate generally to the field of haptic feedback, and more particularly, to equipment that is used to measure surgical apparatus insertion force and provide haptic feedback in an magnetic resonance imaging (MRI) guided environment.
MRI-based medical diagnosis and treatment paradigm capitalizes on the novel benefits and capabilities created by the combination of high sensitivity for detecting tumors, high spatial resolution and high-fidelity soft tissue contrast. This makes it an ideal modality for guiding and monitoring medical procedures including but not limited to needle biopsy and low-dose-rate permanent brachytherapy seed placement. MRI compatibility necessitates that both the device should not disturb the scanner function and should not create image artifacts, and that the scanner should not disturb the device functionality. Generally, the development of sensors and actuators for applications in MR environments requires careful consideration of safety and electromagnetic compatibility constraints.
A number of MRI-guided surgical procedures may be assisted through mechatronic devices that present more amiable solution than traditional manual operations due to the constraints on patient access imposed by the scanner bore. However, the lack of tactile feedback to the user limits the adoption of robotic assistants.
Often the interventional aspects of MRI-guided needle placement procedures are performed with the patient outside the scanner bore due to the space constraint. Removing the patient from the scanner during the interventional procedure is required for most of the previously developed robotic systems. There is a need for needle motion actuation and haptic feedback in order to greatly improve the targeting accuracy by enabling real-time visualization feedback and force feedback. It may also significantly reduce the number of failed insertion attempts and procedure duration.
During needle interventional procedures, traditional manual insertion provides tactile feedback during the insertion phase. However, the ergonomics of manual insertion are very difficult in the confines of an MRI scanner bore. The limited space in closed-bore high-field MRI scanners requires a physical separation between the surgeon and the imaged region of the patient. In addition to the ergonomic consideration, by allowing the surgeon to operate outside the ore they would have access to seeing MRI images, navigation software displays, and other surgical guidance information during needle placement. For example, in a biopsy case, real-time MRI images would be shown to the surgeon and augmented with guidance information to help assist appropriate positioning. In brachytherapy radioactive seed placement, information including real time dosimetry would be made available. Force feedback would help to train inexperienced surgeon to learn important surgical procedures and significantly increase the in-situ performance.
Many variants of force sensors are possible, based on different sensing principles and application scenarios. A hydrostatic water pressure transducer was developed to infer grip force and a 6-axis optical force/torque sensor based on differential light intensity was used for brain function analysis. A large number of fibers are necessary in this design and its nonlinearity and hysteresis are conspicuously undesirable. A novel optical fiber Bragg grating sensor was developed and it is MRI-compatible with higher accuracy than what is typically necessary and has high cost support electronics. None of the aforementioned force sensors (except the high-cost fiber Bragg sensor) satisfy the stringent requirement for needle placement in MR environment. There is a need for a cost-effective MRI-compatible force sensor.
The needs set forth herein as well as further and other needs and advantages are addressed by the present embodiments, which illustrate solutions and advantages described below.
In one embodiment, the system of these teachings includes a master robot/haptic device providing haptic feedback to and receiving position commands from an operator, a robot controller receiving position information and providing force information to the master robot/haptic device, a navigation component receiving images from an MRI scanner, the navigation component providing trajectory planning information to the robot controller, a slave robot driving a needle, the slave robot receiving control information from the robot controller, and a fiberoptic sensor operatively connected to the slave robot; the fiberoptic sensor providing data to the robot controller; the data being utilized by the robot controller to provide force information to the master robot/haptic device.
In one instance, the present teachings include a fiberoptic force sensor and an apparatus for integrating the fiberoptic sensor into a teleoperated MRI-compatible surgical system. One embodiment of the sensor has hybrid (one axis force and two axis torque) sensing capability designed for interventional needle based procedures. The apparatus of the present teachings includes, but is not limited to force monitoring and haptic feedback under MRI-guided interventional needle procedures, which significantly improves needle insertion accuracy and enhance operation safety.
The system of the present embodiment includes, but is not limited to, system arrangement in MRI environment, an optic force sensor, a modular haptic needle grip, teleoperation control algorithm, a robotic needle guide and force feedback master device.
Other embodiments of the system and method are described in detail below and are also part of the present teachings.
For a better understanding of the present embodiments, together with other and further aspects thereof, reference is made to the accompanying drawings and detailed description and its scope will be pointed out in the appended claims.
a and
a is pictorial depicting one embodiment of the light reflection by spherical mirror from central emitter fiber, and
a and 8b are pictorials depicting one embodiment of an interferometry force sensor interface;
a is a pictorial representation of forces acting on a needle, and
a and
a is a pictorial representing one embodiment of an MRI-compatible needle insertion module, and
a is a pictorial representing one embodiment of a needle rotation unit, and
a is a pictorial representing one embodiment of a needle driver with lateral needle force sensing,
a is a pictorial representation of a 1-DOF haptic master device, and
The present teachings are described more fully hereinafter with reference to the accompanying drawings, in which the present embodiments are shown. The following description is presented for illustrative purposes only and the present teachings should not be limited to these embodiments.
In this document, needle is defined as long-shaft surgical instrumentation that provides axial translational and rotation motions and interact with soft tissues, including but not limited to medical needles, electrodes, ablation probes, tissue sensors, tubes, guide sleeves, and canulae.
A “robot,” as used herein, is an electro-mechanical or mechatronie device which is guided by computer or electronic programming.
A “master-slave” system, as used herein, refers to a system in which the operator manipulates a “master” device and the operation of the “master” device is translated into instructions provided to the “slave” robot, the instructions resulting in the “slave” robot performing a task.
“Compatible with the MRT environment” or “MRI-compatible,” as used herein, refers to devices that substantially preserve the image quality of the scanner and whose operation is substantially not affected by the high field MRT environment.
“Light,” as used herein, refers to electromagnetic radiation without limitation to visible wavelength.
A “force sensor,” as used herein, refers to a sensor that measures force and/or torque along or about one or more axes.
One specific application of the system and apparatus is a semi-automated needle guide for MRI-guided prostate brachytherapy and biopsy with haptic feedback. These teachings can be generically applied to other procedures including needle-based percutaneous procedures under other medical imagers, including but not limited to ultrasound, computed tomography (CT), fluoroscopy, X-ray.
In one embodiment, to overcome the loss of tactile feedback in a robot-assisted insertion, needle tip force information, these teachings present a teleoperated force feedback system with fiberoptic force/torque sensor, to be integrated with a robotic needle guide for MRI-guided prostate needle placement. A navigation and control framework integrated with an MRI-compatible fiberoptic force sensor embodiment can be leveraged to close the sensing and control loop in a teleoperation manner.
In one system architecture to utilize a haptic interface in MM as shown in
In one embodiment of the system architecture shown in
In one embodiment, the master 102 device resides outside the MRI scanner room. In one configuration, it resides in the adjacent console room. In an alternate embodiment, one or more of the haptic master 102 and navigation software interface 104 are in a remote location. Master 102 receives force control signals corresponding to the sensed forces from sensor 134. The forces may be directly fed to the master or augmented before being fed back to operator 144 who interacts directly with master 102.
In one embodiment, both an MRI-compatible master device 202 and an MRI-compatible slave robot 226 are located inside the MRI scanner room as shown in
In a further embodiment, shown in
In one embodiment, a direct force feedback algorithm as shown in
In one embodiment, the teachings are used to control percutaneous needle or other surgical tool insertion. A biopsy needle-like haptic gripper 502 as shown in
Generally, the needle has 3-DOF Cartesian motion. In one embodiment, rotation of the needle about its axis is employed to improve the targeting accuracy and reduce insertion force. Alternatively, rotation may be used for active steering of the needle along a specified path or for correction of a path deviating from the target. Needle rotation may be controlled manually with or without haptic feedback. In one embodiment, needle rotation is controlled autonomously. In a further embodiment, needle rotation is autonomously controlled to steer the needle path to compensate for errors in needle placement. The needle may be steered or otherwise controlled based on the tip bevel angle, pre-curved cannulas or stylets, manipulation of the needle base, or other means. In an alternate configuration, the needle may be rotated continuously to minimize needle deflection during insertion. In one embodiment, needle rotation and translation can implemented to steer the needle using spatial duty-cycle based approach. The targeting error in Cartesian space can be used to determine the needle curvature using inverse kinematics. The ratio between this curvature over the maximum curvature is the input to trajectory planner that provides the control strategy between needle rotation angle and rotation velocity. The planned relationship between rotation position and velocity is an insertion velocity independent control that can steer the needle to target position by closed-loop control. The position information of the needle can be provided by optical-flow based tracking or other tracking and segmentation methods. Alternatively, needle tip position can be estimated using a series of MRI transverse needle void image slices, the known needle base position and needle length. Each transverse needle void image slice can be segmented to localize the position of needle void. According to the 3D information assimilated from the images, tip estimation can be posed as a boundary value problem for Euler-Bernoulli beam. Beam bending theory or spline minimization method can estimate the shape of needle in terms of minimum energy. In particular, thin plate spline can be used as basis function for representing coordinate mappings. Force sensing may be incorporated into the needle steering algorithm.
In one embodiment, one or more buttons or other user inputs 506 and 516 on the gripper are used to control the robot. In one configuration, the operator can push the first button 506 to start/stop the axial rotation of the needle and the second button 516 is used to fire the biopsy gun when it is in target position. Alternatively, the buttons can be used to select targets or to constrain the needle motion to 1-DOF insertion along the needle axis needle is appropriately aligned. In one embodiment, the robotic guide aligns the needle axis, and the needle is then inserted along that axis with force feedback using the master manipulator device. More generally, other buttons, switches, joysticks, or other input devices can be used to control many other modular and user-defined motions. The additional interfaces may be integrated into the haptic master device or in a separate device.
The optical sensing mechanism in one embodiment shown in
Redundant measurements help to minimize the measurement uncertainty, signal drifting and environmental noise. Light intensity may be modulated to reduce the effect of ambient light and other external disturbances.
In one embodiment, the light signal emitted from a high-output infrared LED along fiber 606 is reflected by a 9 mm diameter concave spherical mirror 614. (It should be noted that the choice of light source, the dimensions used in this exemplary embodiment for the choice of components are not limitations of these teachings.) Alternatively, laser or other light sources may be used. The emitting position of the LED is designed to be within desired range of the focus point of the mirror, so the reflected light travels back to the emitting side with maximal intensity, where eight fiberoptic photodiodes with appropriate wavelength sensitivity are in circular pattern to detect the reflected light. The light is transmitted through the glass optical fibers 604 with 125 μm cladding diameter to the electronic board outside of the scanner room. All fibers are contained in a ribbon cable and conveniently couple to the controller through a single multi-fiber MTP connector. The glass fibers are inserted to the fiber holder whose inner holes are bonded with glue. The fiber jackets at the end of the fiber holder (3 mm long) are stripped off and tips are polished with fine sand papers to maximize the received light.
The response of these optical sensors as a function of the distance to the mirror has two segments: the first linear and sensitive segment in the range below 0.6 mm, and a low and decreasing sensitive segment for the higher range above 1 mm. Since a linear response is desired, in one embodiment the sensing part is kept to be within the first segment of the response curve. To guarantee high sensitivity and linearity of the sensor, the flexure deflection should be kept within the linear response segment in both directions. It is also desirable to have small deflection to obtain high stiffness and bandwidth. A plastic screw 620 is used to fix the mirror bracket 618. The simple and accurate adjustment structure can translate the mirror 614 into/out of body of the flexure 608. The dimension of one embodiment of the sensor is 36 mm in height and 25 mm in diameter and it weights 36 g equipped with 4 m optical fiber for scanner room communication.
Alternate fiber types, mirror types, light sources, light receivers, and connectors may be used and are part of these teachings. In a further configuration, the LED or laser light sources and the photodiodes or other photodetectors are located on a circuit board attached directly to component 602. Light guides or short fibers may be used, or the light may be directly transmitted to the mirror and reflected directly onto the photodetectors. In a further configuration, a position sensitive detector (PSD), CCD, or other multi-element photodetector may be utilized to determine the change in light distribution reflected from mirror 614.
Redundant measurements help to minimize the measurement uncertainty, signal drifting and environmental noise. Light intensity may be modulated to reduce the effect of ambient light and other external disturbances.
The design of flexure 608 is configured to provide force and torque sensitivity in the desired directions while minimizing effects of other forces and torques. One embodiment of the flexure 608 is capable of sensing axial force and lateral torques with high accuracy while tolerating off-axis forces and torques. Two parallelogram-like segments 610 of helical circular engravings in the structure have intrinsic axial/lateral overload protection capability and minimize the effects of lateral forces and axial torques. Other flexure designs can be used for other desired fore/torque combinations. The structure of the sensor is simple and facilitates fast and low cost manufacturing. The flexure is compact and simple, and it allows simpler fiber cables and electronics.
Transverse sensitivity is an important design factor of force sensor. To achieve minimal transverse sensitivity, it is preferable for the flexure to be stiffer to the forces applied in the other directions. The flexible hinges structure in this design with low thickness-to-width ratio would generate good direction selective stiffness. A novel flexure mechanism was designed and the finite element analysis was performed to aid the optimization of the design parameters. The flexure converts the applied forces and torques into displacement of the mirror thus generating a light intensity change. The structure should be simple to facilitate machining process. In order to guarantee measurement isotropy, a cylinder structure with engraved elastic curves was used in one embodiment. In one configuration, the flexure is machined using traditional machining processes. Alternatively, the sensor may be molded. One configuration of the sensor is single use and disposable. In one embodiment, the flexure structure may be constructed from rigid, MRI-compatible materials that are suitable for common sterilization practices used in a hospital setting. Building materials include, but are not limited to high strength plastics (including PEEK and polyetherimide), aluminum alloys, composites, ceramics, titanium alloys, etc. By implementing materials such as these, the image quality of the scanner can be preserved, allowing the user to take full advantage of in situ image guidance. In one configuration, the sensor is entirely non-metallic. Transverse sensitivity is an important design factor of force sensor. To achieve minimal transverse sensitivity, it is preferable for the flexure to be stiffer to the forces applied in the other directions. The flexible hinges structure in this design with low thickness-to-width ratio would generate good direction selective stiffness.
In one embodiment, although not limited thereto, the haptic system comprises an MRI-compatible force sensor which is designed for monitoring forces in the 0-20 Newton range with a sub-Newton resolution. In one configuration of the present teachings, the fiberoptic sensor enables 2-DOF torque measurement and 1-DOF force measurement.
One representative application of the 3-axis force/torque sensor with this range and resolution is for interventional procedures including needle biopsy and brachytherapy inside the MRI scanner. This configuration may be ideal for other needle-based procedures in MRI both with and without robotic assistance. Other configurations may be used for other applications. In one configuration, the fiberoptic sensor is used as a joystick to control a robot motion or interface with software. In another configuration, the sensor is used for rehabilitation or functional imaging studies. One embodiment of this sensor provides 3-DOF force measurement in percutaneous prostate interventions in 3 Tesla closed-bore MRI. Additional applications include other field strengths, open and closed bore MRI scanners and other surgical procedures including needle/electrode insertion during deep brain stimulation and needle based liver ablation. These do not represent the entirety of the potential applications.
One representative application of the 3-axis force/torque sensor with this range and resolution is for interventional procedures including needle biopsy and brachytherapy inside the MRI scanner. This configuration may be ideal for other needle-based procedures in MRI both with and without robotic assistance. Other configurations may be used for other applications. In one configuration, the fiberoptic sensor is used as a joystick to control a robot motion or interface with software. In another configuration, the sensor is used for rehabilitation or functional imaging studies.
In one embodiment of the optical force sensor, a point source is assigned in the focal position 702 as shown in
In one embodiment, the number of receiving fibers 718 in this design is 8, but the minimum number required for this sensor structure is 3. The simple mechanical structure of the flexure allows the deployment of more fibers which guarantees robust, high-fidelity force sensing capability. The fibers may all be at the same distance from the center, or they may be arranged in another configuration. The emitter may be in the center with receivers at the outside. Alternatively, there may be multiple switched or otherwise distinguished emitters with one or more receivers.
Redundant measurements help to minimize the measurement uncertainty, signal drifting and environmental noise. Light intensity may be modulated to reduce the effect of ambient light and other external disturbances.
In one calibration process, the sensor is mounted on a vibration isolating optical table using designed fixtures. Calibrated brass weights incrementally apply 100 g axial forces (up to 9.8 Newton) on the sensor. The 8 channel voltage outputs are recorded for 10 seconds for each configuration. The corresponding recorded voltage values were averaged to get the mean voltage output for each channel. The same procedure was performed to decreasingly unload the weight to evaluate hysteresis. Alternative calibration processes include using shape from motion techniques.
By taking advantage of this force sensor, the in-vivo insertion force can be monitored, but alternatively, this system can take advantage of it to perform active force control during the insertion procedure. Active force control and monitoring would provide high fidelity surgery and reduced operational time. The sensor can be used to measure tissue interaction forces with electrode tip or needle shaft and tip, detection of obstructions, guidance for steering needle/electrodes, and provide a sensing input for a cooperatively controlled robot, input for functional neurology studies, rehabilitation device.
One specific application is a semi-automated needle guide for MRI-guided prostate brachytherapy and biopsy with haptic feedback. Additional uses include a generic multi-axis force/torque sensor to monitor surgical intervention force or the human grip force during neural rehabilitation or other purposes. The sensor may also have applications in environments where electronics cannot be tolerated, i.e. industrial, dangerous and explosive environments and explosion prevention environment.
Alternate embodiments of fiberoptic force sensing in MRI can be implemented using wavelength-modulated methods including Fiber Bragg grating (FBG) or phase modulated method including Fabry-Perot interferometer (FPI) based strain sensing (see, for example, Yoshino, T., Kurosawa, K., Itoh, K., Ose, T., Fiber-Optic Fabry-Perot Interferometer and its Sensor Applications, IEEE Transactions on Microwave Theory and Techniques, Volume: 30 Issue: 10, October 1982, pp. 1612-1621, and U.S. Pat. No. 6,173,091, both of which are incorporated by reference herein in their entirety for all purposes). The present teachings include a miniature fiberoptic force sensor to measure needle insertion forces in MRI-guided prostate interventions. In one embodiment shown schematically in
In an alternative embodiment, FPI optical strain gauges or Fiber Bragg grating strain gauges are embedded into a flexure. In one embodiment of these teachings, they are configured to measure 3-DOF forces or torques.
The fiberoptic force sensor embodiments in these teachings the sensor may be directly connected to the robot controller or another sensor interface inside the MRI scanner room. In an alternate embodiment, the fibers are passed out of the MRI scanner room and coupled to a standalone sensor interface or other sensor interface outside the scanner room.
a depicts forces interacting on a needle during insertion. Needle 902 punctures skin or other tissue interface 904 and is inserted into tissue 906. The forces include axial forces along the needle axes and friction forces along the surface 908 of the needle. Forces present on an asymmetric bevel tip 910 will cause the needle to deflect during insertion. In one embodiment, we use these forces to actively control the needle insertion path. In a further embodiment, interactive MRI imaging is used to perform closed loop control of needle insertion. A further embodiment of the present invention uses force information sensed during the needle insertion for classification of tissues. In one configuration, needle forces and MRI imaging are utilized together to classify tissue by type or pathology. Further, forces may be used in conjunction with anatomical imaging for assisting in localization of the needle tip. One configuration of such integrated sensors is one or more FPI of FBG fibers along the needle to measure needle bending and shape. In an alternate embodiment, sensing integrated into the needle is used for localizing the needle and control. A further embodiment of the present invention uses force information sensed during the needle insertion for classification of tissues. In one configuration, needle forces and MRI imaging are utilized together to classify tissue by type or pathology. Further, forces may be used in conjunction with anatomical imaging for assisting in localization of the needle tip.
b shows a representative plot of axial needle insertion force 920 as a function of penetration depth 922 (see, for example, Y. Yu, T. Podder, Y. Zhang, W. S. Ng, V. Misic, J. Sherman, L. Fu, D. Fuller, E. Messing, D. Rubens, J. Strang, and R. Brasacchio, “Robot-assisted prostate brachytherapy,” Medical Image Computing and Computer-Assisted Intervention—MICCAI 2006. 9th International Conference. Proceedings, Part I (Lecture Notes in Computer Science Vol. 4190), (Berlin, Germany), pp. 41-9, Springer-Verlag, 2006, which is incorporated by reference herein in its entirety for all purposes)). When the needle punctures the skin or other tissue interface, such as the capsule of the prostate, a peak in insertion force 926 is present. The present teachings are capable of sensing the insertion forces, including peaks in insertion force at tissue interfaces, and reflecting them back to an operator using a haptic master device.
a depicts an embodiment of these teachings in which a needle insertion robot resides in the MRI scanner. The patient 1002 is located inside the MRI scanner 1004 which resides in MRI scanner room 1006. During imaging and an image-guided surgical intervention, patient 1008 is inside the MRI scanner bore 1008 on the bed, table, or couch 1010. An MRI-compatible robotic device 1014 is place inside bore 1008 of scanner 1004. Robot 1014 sits on base 1016. In one embodiment, the robot 1014 is a slave manipulator in a teleoperated system. In a further embodiment, robot 1014 controls placement of needle or surgical tool 1020 based in whole or in part by the motion of a haptic master controlled by the operator. One application of the present teachings is for prostate interventions including diagnosis with biopsy and treatment with brachytherapy. In these applications, needle 1020 is inserted into the entry point 1024 of the patient 1008 while acquiring real-time or interactive MRI image updates from MRI scanner 1004. In one embodiment, robot 1014 performs transperineal prostate needle placement through the patient's perineum 1024.
One embodiment of the Cartesian motion platform 1104 contains 3-DOF motion. Linear slide 1108 provides motion along the axis of the scanner and linear slide 1112 provides lateral motion with respect to the scanner. Both axes 1108 and 1102 are actuated by linear piezoelectric ceramic motors and position is sensed by optical encoders. Alternate embodiments may use other joint encoding sensors including fiberoptics and linear potentiometers. Vertical motion mechanism 1116 is actuated by rotary piezoelectric motor 1120 through lead screw 1122.
One embodiment of the needle drive module 1102 provides 3-DOF motion including cannula rotation and insertion (2-DOF) and stylet translation (1-DOF). The independent rotation and translation motion of the cannula can increase the targeting accuracy while minimize the tissue deformation and damage. The module sits on platform 1130 that mounts to base stage 1104. Linear motion is provide along linear slide 1132 by piezoelectric motors. Joint position is sensed by optical encoder 1134 which reads encoder strip 1136. The inner stylet of the needle is controlled independently of the outer cannula by module 1140. Motor 1142 translates the stylet relative to the needle and encoder 1144 measures position. The hub 1148 of needle 1150's stylet contacts interface component 1152. Interface 1152 pushes the stylet hub 1148 relative to needle 1150. In one embodiment, interface 1152 incorporates force sensing for the axial needle insertion force. Needle rotation module 1160 allows for rotation of the needle about its axis as it is driven into the tissue. In one embodiment, module 1160 also includes tracking fiducials for locating the robot inside the MRI scanner to assist in registration and control. Module 1160 include a rotary piezoelectric motor that turns collect or needle clamp 1162 which is mechanically coupled to needle 1150. Encoder 1164 measure needle rotation. A force sensor 1170 couples to needle 1150 through interface 1172. One embodiment of force sensor 1170 is described in
An embodiment of the needle driver module 1102 provides for needle cannula rotation, needle insertion and cannula retraction to enable the brachytherapy procedure with the preloaded needles. The device mimics the manual physician gesture by two point grasping (hub and base) and provides direct force measurement of needle insertion force by fiberoptic force sensors. To fit into the seamier bore, the width of the driver is limited to 6 cm and the operational space when connected to a base platform is able to cover the perineal area using traditional brachytherapy 60 mm×60 mm templates. The robot maximizes the compliance with transperineal needle placement, as typically performed during a TRUS guided implant procedure. This design aims to place the patient in the supine position with the legs spread and raised with similar configuration to that of TRUS-guided brachytherapy.
In further embodiment of these teachings, the following mechanisms are implemented to minimize the consequences of system malfunction. a) Mechanical travel limitations mounted on the needle insertion axis that prevents linear motor rod running out of traveling range; b) Software calculates robot kinematics and watchdog routine that monitors robot motion and needle tip position; and c) Emergency power button that can be triggered by the operator. The robot components of one embodiment are primarily constructed of acrylonitrile butadiene styrene (ABS) and acrylic. Ferromagnetic materials are avoided. Limiting the amount of conductive hardware ensures imaging compatibility in the mechanical level. In one configuration, only the needle clamp and guide (made of low cost ABS plastic) have contact with the needle and are disposable.
During needle placement procedure, to accomplish needle insertion, a needle can be mounted on the slave robot. For one embodiment, the slave robot can have 4-DOF which provides the 1-DOF needle translation and Cartesian base positioning. One embodiment of the needle drive module 1202 shown in
Once a needle, preloaded brachytherapy needle, or biopsy gun is inserted into collet 1230, the collet can rigidly clamp the outer cannula shaft 1206. In the case of a solid needle, guide wire or other instrument for insertion, the collet 1230 clamps onto needle 1206 and there is no differentiation between inner stylet and outer cannula. Since the linear motor 1222 is collinear with the collet and shaft, an offset must be induced to manually load the needle. The apparatus shown in
c illustrates a block diagram of an embodiment of a slave robot. As shown in the block diagram
By actively steering and inserting needles, the needle can target 3D position and the force measurement threshold would avoid non-soft tissue interaction. To compensate for the needle deflection, the needle could be axially rotated. The needle deflection estimation algorithm can be used to find the appropriate insertion depths at which needle rotations are to be performed.
a shows one embodiment of the needle clamping and rotation apparatus. Needle 1318 is clamped to collet sleeve 1308. Pulleys 1304 and belt 1306 mechanically couple sleeve 1308 to rotary actuator 1302. Eccentric tensioner 1300 tightens belt 1306. Encoder 1314 precisely measures needle rotation angle.
Dynamic global registration between the robot and scanner is achieved by passive tracking the fiducial frame 1320 in front of the robot. The rigid structure of the fiducial frame is made of ABS and seven MRI fiducials 1316 are embedded in the frame to form a Z shape passive fiducial. Any arbitrary MR image slicing through all of the rods provides the full 6-DOF pose of the frame, and thus the robot, with respect to the scanner. Thus, by locating the fiducial attached to the robot, the transformation between the patient coordinate system (where planning is performed) and that of the needle placement robot is known. To enhance the system reliability and robust, multiple slices of fiducial images are used to register robot position using principal component analysis method. The end effector location is then calculated from the kinematics based on the encoder positions.
The needle driver allows a large variety of standard needles utilizing a clamping device shown in
a illustrates one embodiment of a 2-DOF lateral force sensor coupled to the needle driver module. Needle guide 1402 attaches to needle driver module 1404. Sensor flexure 1406 has needle guide hole 1408 for needle 1410. Hole 1408 may have an insert to match various needle sizes or be sized for a specific needle diameter. The flexures in 1406 allow small amount of lateral 2-DOF motion to sense forces not mal to the needle axis. Strain sensors 1412 are integrated into the flexure. In one configuration, strain sensors 1412 are FPI sensors.
a illustrates an embodiment of a 1-DOF linear MRI-compatible haptic interface that serves as a master device. This is a representative embodiment of a haptic mater device for MRI-guided interventions and may take on other forms including additional degrees of freedom, and said linear degrees of freedom may be linear or rotary. An actuator 1500 is mounted on base plate 1514 and moves platform 1512. In one embodiment, actuator 1500 is a high stiffness piezoelectric linear actuator; in alternative embodiments it may take the foini of piezoelectric, pneumatic, hydraulic, electromechanical, or other actuation. Position sensor 1502 is mounted on the top plate 1512. In one embodiment, sensor 1502 is an optical encoder with linear strip 1504. In alternative embodiments, the sensor 1502 may be a reflective or through beam optical encoder, a potentiometer, a laser distance transducer, or other measurement means. An application-specific modular handle 1510 provides the user interface. The handle may be made to mimic the feel of a traditional tool. For example, handle 1510 demonstrates an embodiment for biopsy needle insertion. Force applied by a human operator on handle 1510 is measured by a sensor 1508. In one embodiment, sensor 1508 is a 1-DOF force sensor; in alternate embodiments, sensor 1508 may measure other DOF of forces and torques. In one embodiment of the system, force sensing is implemented as fiberoptic force sensing; alternatively forces and torques bay be measured by alternative means including but not limited to optical, resistive, capacitive, and piezoelectric sensors.
In one embodiment of the haptic device, the controller provides force feedback in an admittance control law where the force applied to handle 1510 is regulated in a closed loop controller using sensor 1508 and actuator 1500. The 1-DOF device may be used as a master haptic interface for needle insertion. In one embodiment, needle insertion force is sensed by a sensor on the slave robot or needle and that force is fed back to the operator through handle 1510. That force may be scaled to augment the user feedback experience. The operator applies force to handle 1510 which causes platform 1512 to move with respect to base 1514. Sensor 1502 measures the change in motion and commands the slave robot to follow. The bilateral teleoperator control scheme allows an operator to manipulate an MRI-compatible master from within the MRI scanner room and control the insertion of a needle with the sensation that they are manually performing the procedure. In a further embodiment, the operator only controls the motion in the insertion direction, and a robot controller autonomously controls additional DOF to control the needle trajectory and tip placement. In one embodiment, the robot controls the rotation of the needle during insertion to steer the needle tip based on forces applied to the beveled tip. Needle trajectory control may be used to automatically follow a predetermined path while the user only controls an insertion distance parameter. Alternatively, the needle path may be controlled to compensate for needle or tissue deformation based on models and or interactive image updates.
An alternative embodiment of a haptic interface in
c depicts a block diagram of a master device. An MRI-compatible actuating component 1576 drives a base component 1578 whose motion is measured by an actuation sensing component 1580. A haptic interface 1570 connects to a force sensor 1572 and the top component resides on a motion carriage 1574. In one configuration, force sensor 1572 is an optical sensor that measures user interaction forces on handle 1570. A robot controller uses information from sensor 1572 to regulate the applied force by controlling actuating component 1576. The position sensed by sensor 1580 is used to control the position of a slave robot.
Briefly, one procedure incorporating the invention for MRI-guide transperineal prostate biopsy is described as follows:
When the needle tip reaches the target, a secondary operation may be performed. In the case of biopsy, a biopsy gun may be fired and a tissue sample acquired. For brachytherapy seed placement using a preloaded needle, the cannula may be retracted to place the seeds. In one embodiment, a needle driver module's two linear motion stages move in a coordinated motion to place the seeds. This process is repeated for all needle insertions in the given procedure.
For the purposes of describing and defining the present teachings it is noted that the term “substantially” is utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The term “substantially” is also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.
While the present teachings have been described above in terms of specific embodiments, it is to be understood that they are not limited to these disclosed embodiments. Many modifications and other embodiments will come to mind to those skilled in the art to which this pertains, and which are intended to be and are covered by this disclosure. It is intended that the scope of the present teachings should be determined by proper interpretation and construction of the claims, as understood by those of skill in the art relying upon the specification and the attached drawings.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US10/56020 | 11/9/2010 | WO | 00 | 6/27/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61259376 | Nov 2009 | US |
