Puncture needle track prediction and master-slave control method based on force measurement

Abstract

The invention belongs to the technical field related to master-slave control of medical equipment, and discloses a puncture needle track prediction and master-slave control method based on force measurement, which comprises the following steps of: (1) measuring bending moment and transverse force in two orthogonal planes of a puncture needle tail end coordinate system and axial force along a puncture needle in real time; (2) calculating to obtain a simulation load loaded on the interaction part of the puncture needle and the soft tissue; (3) respectively solving the predicted positions of the puncture needle on the two corresponding orthogonal planes; and (4) the predicted position and the expected position are subtracted, the obtained difference value is multiplied by a proportionality coefficient to obtain two pieces of force sense information, then the two pieces of force sense information and the axial force are transmitted to the master-end operation equipment, the master-end operation equipment carries out force sense reproduction according to the received information, the force sense information serves as an operation instruction of an operator to the slave-end robot, and the operation instruction of the operator to the slave-end robot is completed. And the attitude of the slave end robot is controlled to reduce the difference value between the predicted position and the expected position. According to the invention, the real-time performance is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to master-slave control of medical devices, and more specifically, relates to a method for predicting the trajectory of a puncture needle and master-slave control based on force measurement. Background Art

[0002] During percutaneous puncture surgery, most require imaging devices such as CT to assist in confirming the position of the puncture needle. The radiation damage to medical staff and patients cannot be ignored. Master-slave control in medical surgery can support doctors to remotely operate through technical means, avoid the radiation damage to medical staff during the operation, effectively reduce the high-cost training resources of medical staff, reduce the workload of medical staff, and at the same time solve the problem of uneven geographical distribution of medical resources.

[0003] During manual puncture, the operator perceives the penetration depth of the puncture needle and discriminates tissue characteristics by sensing the magnitude of the force along the needle axis of the puncture needle. The lateral force level on the needle body of the puncture needle is small and not obvious. The position of the puncture needle in the transverse plane needs to be confirmed by devices such as CT. During the puncture surgery with master-slave control, a force / torque sensor is usually installed at the connection between the puncture device and the robot, and the interaction force with the human tissue measured during the operation is directly and truly transmitted to the master-end operating device to enhance the force sense immersion during the master-slave control process. Combining the measured axial force along the puncture needle and the CT device to control the puncture device, this process requires continuous use of the CT device to determine the position of the puncture needle, and frequent use of the puncture device will cause radiation damage to medical staff and patients, and there is a certain delay resulting in poor real-time performance. Summary of the Invention

[0004] In view of the above defects or improvement requirements of the prior art, the present invention provides a method for predicting the trajectory of a puncture needle and master-slave control based on force measurement, aiming to solve the problem of poor real-time performance of the existing master-slave control method.

[0005] To achieve the above object, according to one aspect of the present invention, a method for predicting the trajectory of a puncture needle and master-slave control based on force measurement is provided. The method includes the following steps:

[0006] (1) Use a force sensor provided at the end of the puncture needle to measure the bending moment, lateral force, and axial force along the puncture needle in two orthogonal planes of the coordinate system at the end of the puncture needle in real time;

[0007] (2) Real-time calculate the measured force and torque information to respectively obtain the simulated loads applied to the interaction part between the puncture needle and the soft tissue on two orthogonal planes;

[0008] (3) Solve the position of the puncture needle in the corresponding two orthogonal planes, that is, the predicted position, according to the magnitude and direction of the simulated loads respectively;

[0009] (4) Subtract the predicted position from the desired position, multiply the difference between the obtained predicted position and the desired position by a proportionality coefficient to obtain two force sense information, and then transmit the two obtained force sense information and the measured axial force to the master manipulator. The master manipulator performs force sense reproduction according to the received information, uses the force sense information as the operation instruction of the operator on the slave robot, and further controls the posture of the slave robot to reduce the difference between the predicted position and the desired position.

[0010] Further, after step (4), the following steps are further included: confirming the actual position of the puncture needle through a CT device, and the operator further adjusts the posture of the slave robot according to the confirmed actual position through the master manipulator.

[0011] Further, taking one of the two orthogonal planes as an example, according to the lateral force F in the XY plane and the bending moment M collected in real time by the force sensor at the end of the puncture needle, simulate the type of the lateral action load of the soft tissue on the puncture needle, and calculate the magnitude of the simulated load applied to the puncture needle. The corresponding formula is: s ∑F

[0012] ∑F y =0; ∑M z =0.

[0013] Further, solve the displacement magnitude of the puncture needle in the Y direction in the XY plane in real time according to the type and magnitude of the load.

[0014] Further, the displacement calculation formulas corresponding to different types of loads are respectively:

[0015] Concentrated acting force F t :

[0016] Uniformly distributed load q0:

[0017] Triangular load q1:

[0018] Parabolic load q2:

[0019] In the formula, E is the Young's modulus of the puncture needle, and I is the moment of inertia of the puncture needle.

[0020] Further, when the puncture depth of the puncture needle is b, the estimated coordinates (b, y, z) of the needle tip are obtained according to the data collected and processed in real time by the force sensor, and the planned values (b, y d , z d ), and the difference between the coordinates of the two in the plane of x = b is (Δy = y - y d , Δz = z - z d) The positive or negative value and magnitude of this value reflect the direction and distance between the predicted value and the expected value.

[0021] Further, combining the axial real force F measured by the force sensor x , the force sense information fed back from the distal end to the master end includes three force sense information, namely two processed force sense information and one real axial force:

[0022] F = [kΔy kΔz F x

[0023] wherein, the proportional coefficient k can be adjusted, kΔy and kΔz are used as the force sense information for prompting operations, and F x is the real force along the axial direction of the puncture needle.

[0024] Generally speaking, compared with the prior art by the above technical solution conceived by the present invention, the puncture needle trajectory prediction and master-slave control method provided by the present invention mainly has the following beneficial effects:

[0025] 1. Effectively estimate the displacement of the puncture needle in two two-dimensional planes in real time according to the relatively small lateral force and bending moment information, and combine the two two-dimensional plane information to realize the real-time estimation of the displacement of the puncture needle in the lateral plane at any puncture depth, improving the real-time performance.

[0026] 2. Subtract the predicted position from the expected position, multiply the difference between the obtained predicted position and the expected position by the proportional coefficient to obtain two force sense information, and then transmit the obtained two force sense information and the measured axial force to the master end operating device. The master end operating device performs force sense reproduction according to the received information, uses the force sense information as the operation instruction of the operator for the slave end robot, and further controls the posture of the slave end robot to reduce the difference between the predicted position and the expected position, improving the real-time performance and accuracy.

[0027] 3. By comparing the error between the puncture needle displacement estimation information and the preoperative planning information, it is used as torque feedback to the master operating device to prompt the operator of the position deviation between the current puncture process and the target target point, and then combine the medical imaging information to realize the puncture needle trajectory adjustment operation, further improving the accuracy and reducing the usage frequency of the CT device.

[0028] 4. The method is simple, easy to implement in real time, and has good applicability. Description of the Drawings

[0029] Figure 1 is a schematic diagram of the puncture needle trajectory prediction and puncture surgery master-slave robot system provided by the embodiment of the present invention;

[0030] Figure 2 ​It is a schematic diagram of a force sensor measurement force system during the interaction between a puncture needle and soft tissue provided by an embodiment of the present invention;

[0031] Figure 3 In (a) and (b) of [figure number], they are respectively schematic diagrams of simulating a concentrated load F applied to the puncture needle t and a uniform load q0;

[0032] Figure 4 In (a) and (b) of [figure number], they are respectively schematic diagrams of simulating a triangular load q1 and a parabolic load q2 applied to the puncture needle;

[0033] Figure 5 In (a) and (b) of [figure number], they are respectively schematic diagrams of a puncture needle trajectory prediction and master - slave control method based on force measurement;

[0034] Figure 6 It is a flowchart of a puncture needle trajectory prediction and master - slave control method based on force measurement.

[0035] In all the drawings, the same reference numerals are used to represent the same elements or structures, where: 1 - slave robot, 2 - force sensor, 3 - puncture needle, 3 - 1 - predicted puncture trajectory, 3 - 2 - planned puncture trajectory, 4 - fixing part, 5 - soft tissue, 6 - master operation device. Detailed implementation manners

[0036] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] The present invention provides a puncture needle trajectory prediction and master - slave control method based on force measurement. The method uses the information of the force sensor installed near the puncture device in the master - slave puncture surgery to measure the interaction force with the punctured soft tissue, and estimates the displacement of the puncture needle in the transverse plane in real time. At the same time, according to the positive or negative and magnitude of the error between the puncture needle in the transverse section and the set target value, after processing, it is used as a prompt message for torque feedback transmitted to the master operation device, so that the operator can confirm the difference between the position of the puncture needle in the transverse plane and the target position through the force feedback information, and with the assistance of medical imaging information, jointly complete the adjustment operation of the puncture needle attitude.

[0038] The present invention deeply utilizes the data collected by sensors for recording the interaction forces and moments between soft tissues. First, based on the relatively small lateral force and bending moment information, effective estimation of the displacement of the puncture needle in two two-dimensional planes is achieved. By combining the information of the two two-dimensional planes, the displacement of the puncture needle in the lateral plane at any puncture depth can be estimated. Second, by comparing the error between the estimated displacement information of the puncture needle and the planned information, it is used as a moment feedback to the master operating device to prompt the operator of the position deviation between the current puncture process and the target point, and then the adjustment operation of the puncture needle trajectory is achieved in combination with medical imaging information.

[0039] Please refer to Figure 1 and Figure 6 , the method mainly includes the following steps:

[0040] Step 1, use the force sensor set at the end of the puncture needle to measure the bending moment, lateral force and axial force along the puncture needle in two orthogonal planes of the coordinate system at the end of the puncture needle in real time.

[0041] Please refer to Figure 2 , during the interaction between the puncture needle and soft tissues, the force sensor measurement system includes a slave robot 1, a force sensor 2, a fixing part 4, a puncture needle 3 and a master operating device 6. The end of the slave robot 1, the force sensor 2 and the end of the puncture needle 3 are connected together through the fixing part 4 without relative displacement. The puncture needle 3 is used to penetrate into the soft tissue 5.

[0042] The puncture needle is an oblique-tip puncture needle, and the ratio of its length to diameter is large, which conforms to the characteristics of the long axis. The needle insertion speed during the puncture operation is slow, so it can be regarded as a quasi-static process at any moment. In the XY plane of the coordinate system at the end of the puncture needle, the deflection displacement of the puncture needle in the Y direction due to the influence of the lateral force of the soft tissue on the puncture needle within the penetration depth b. At this time, the data collected by the force sensor shows the lateral force Fs, the bending moment M and the force F along the axial direction of the puncture needle x . As Figure 3 shown is a schematic diagram of the concentrated load F t and the uniform load q0 simulated and loaded on the puncture needle, Figure 4 shown is a schematic diagram of the triangular load q1 distributed force and the parabolic load q2 simulated and loaded on the puncture needle. The above four are only schematic diagrams of the load forces simulated and loaded on the puncture needle. In the actual prediction process, the free combination form of the above four loads is selected to predict the puncture needle trajectory.

[0043] Step 2, calculate and obtain the simulated load applied to the interaction part between the puncture needle and the soft tissue in real time through the measured force and moment information.

[0044] According to the lateral force F in the XY plane collected in real time by the force sensor at the end of the puncture needle sWith the bending moment M, simulating the type of lateral acting load of the soft tissue on the puncture needle, and calculating in real time the magnitude of the simulated load applied to the puncture needle by computer software. Specifically, there are:

[0045] ∑F y =0;∑M z =0

[0046] Specifically, in another plane within two orthogonal planes, the lateral force F s in the XZ plane collected in real time by the force sensor at the end of the puncture needle and the bending moment M can also calculate in real time the magnitude of the simulated load applied to the puncture needle by computer software. Specifically, there are:

[0047] ∑F z =0;∑M y =0

[0048] Step 3: Solve the positions of the puncture needle in the corresponding two orthogonal planes, that is, the predicted positions, according to the magnitude and direction of the simulated load respectively.

[0049] Solve in real time the magnitude of the displacement of the puncture needle in the Y direction in the XY plane according to the type and magnitude of the load. E is the Young's modulus of the puncture needle, I is the moment of inertia of the puncture needle. The influence of different types of loads on the deformation of the puncture needle can be calculated by the following formulas respectively. By the superposition principle, the total deformation of the puncture needle can be obtained by superimposing different types of loads:

[0050] Concentrated force F t :

[0051] Uniform load q0:

[0052] Triangular load q1:

[0053] Parabolic load q2:

[0054] Similarly, solve in real time the magnitude of the displacement of the puncture needle in the Z direction in the XZ plane according to the type and magnitude of the load in the XZ plane. By the superposition principle, the total deformation of the puncture needle can be obtained by superimposing different types of loads.

[0055] Concentrated force F t :

[0056] Uniform load q0:

[0057] Triangular load q1:

[0058] Parabolic load q2:

[0059] Step 4: Subtract the predicted position from the desired position, multiply the difference between the predicted position and the desired position by a proportionality coefficient to obtain two force sense information, and then transmit the two obtained force sense information and the measured axial force to the master operating device. The master operating device performs force sense reproduction according to the received information, uses the force sense information as the operation instruction of the operator on the slave robot, and further controls the posture of the slave robot to reduce the difference between the predicted position and the desired position.

[0060] The operator discriminates the puncture tissue property according to the felt axial force.

[0061] When the puncture needle is at the puncture depth b, the estimated coordinates (b, y, z) of the needle tip can be obtained according to the data collected and processed in real time by the force sensor. For the planned values (b, y d , z d ), the difference between the coordinates of the two in the plane of x = b is (Δy = y - y d , Δz = z - z d ). The positive or negative and magnitude of this value reflect the direction and distance between the predicted value and the expected value. Further use this difference as the force / torque feedback from the slave robot system to the master operator to give a prompt message for puncture needle posture adjustment. Combining with the real axial force F measured by the force sensor x , the force sense information fed back from the slave to the master includes three force sense information: two processed force sense information and one real axial force:

[0062] F = [kΔy kΔz F x

[0063] Among them, the proportionality coefficient k can be adjusted. kΔy and kΔz are used as the force sense information for prompting operations, and F x is the real force along the axial direction of the puncture needle. For the specific implementation method of adjusting the posture of the puncture needle according to the force feedback information, see Figure 5 . Taking the posture adjustment of the puncture needle in the y direction in the XY plane as an example, when the predicted value y has a large offset compared to the planned value y d , as shown in 3-1 for the predicted puncture needle trajectory and 3-2 for the planned puncture needle trajectory, a prompt force information kΔy is generated for the master operating device. The operator manipulates the slave robot to rotate counterclockwise around the insertion point by an angle α according to the prompt information. As the puncture depth of the puncture needle increases, the offset of the puncture needle in the y direction in the XY plane will decrease. The adjustment method in the z direction in the XZ plane is consistent with the adjustment method in the XY plane.

[0064] ​Through real-time processing of the measurement data of the force sensor at the end of the puncture needle, prompt information is fed back to the master operation device to guide the operator to reasonably adjust the posture of the slave robot, increase further correction of the medical imaging device, and control the actual trajectory of the puncture needle to reach the puncture target with as small a deviation as possible to complete the puncture surgery task.

[0065] Step Five, confirm the actual position of the puncture needle through the CT device, and the master operation device further adjusts the posture of the slave robot according to the confirmed actual position.

[0066] Meanwhile, the imaging information in the puncture surgery can be used to further correct the deviation between the predicted value and the actual value of the puncture needle trajectory based on force measurement, and improve the puncture success rate.

[0067] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for predicting the trajectory of a puncture needle and master-slave control based on force measurement, characterized in that The method includes the following steps: (1) Using a force sensor provided at the end of the puncture needle to measure the bending moment, lateral force, and axial force along the puncture needle in two orthogonal planes of the coordinate system at the end of the puncture needle in real time; (2) Solving in real time based on the measured force and torque information to respectively obtain the simulated loads applied to the interaction part between the puncture needle and the soft tissue on two orthogonal planes; (3) Solving the positions of the puncture needle in the corresponding two orthogonal planes, i.e., the predicted positions, respectively according to the magnitudes and directions of the simulated loads; (4) Taking the difference between the predicted position and the desired position, multiplying the obtained difference between the predicted position and the desired position by a proportionality coefficient to obtain two force sense information, and then transmitting the obtained two force sense information and the measured axial force to the master operating device. The master operating device performs force sense reproduction according to the received information, uses the force sense information as the operation instruction of the operator for the slave robot, and further controls the posture of the slave robot to reduce the difference between the predicted position and the desired position.

2. The force measurement-based puncture needle trajectory prediction and master-slave control method according to claim 1, wherein: After step (4), the following steps are further included: Confirming the actual position of the puncture needle through a CT device, and the master operating device further adjusts the posture of the slave robot according to the confirmed actual position.

3. The force measurement-based puncture needle trajectory prediction and master-slave control method according to claim 1, characterized in that: According to the lateral force F in the XY plane collected in real time by the force sensor at the end of the puncture needle s and the bending moment M, simulate the type of lateral acting load of the soft tissue on the puncture needle, and calculate the magnitude of the simulated load applied to the puncture needle. The corresponding formula is: ∑F y = 0; ∑M z = 0.

4. The force measurement-based puncture needle trajectory prediction and master-slave control method according to claim 1, characterized in that: Solving the magnitude of the displacement of the puncture needle in the Y direction in the XY plane in real time according to the type and magnitude of the load.

5. The force measurement-based puncture needle trajectory prediction and master-slave control method according to claim 4, characterized in that: The displacement calculation formulas corresponding to different types of loads are respectively: Concentrated force F t : Uniformly distributed load q0: Triangular load q1: Parabolic load q2: In the formula, E is the Young's modulus of the puncture needle, and I is the moment of inertia of the puncture needle.

6. The force measurement-based puncture needle trajectory prediction and master-slave control method according to claim 1, wherein: When the puncture needle reaches the puncture depth b, the estimated coordinates (b, y, z) of the needle tip are obtained based on the data collected by the force sensor and processed in real time. For the planned values (b, y d , z d ), the difference between the coordinates of the two in the plane of x = b is (Δy = y - y d , Δz = z - z d ). The sign and magnitude of this difference reflect the direction and distance between the predicted value and the expected value.

7. The force measurement-based puncture needle trajectory prediction and master-slave control method according to claim 6, characterized in that: The axial real force F measured by the bonding force sensor x , the force sense information fed back from the end to the main end includes three force sense information, namely, two processed force sense information and one real axial force: F = [kΔy kΔz F x ​ Among them, the proportionality coefficient k can be adjusted. kΔy and kΔz are used as the haptic information for prompting operations, and F x is the real force along the axial direction of the puncture needle.

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