Anti-electromagnetic interference laparoscope positioning device and method

Abstract

The invention relates to the technical field of laparoscope tracking and positioning, and discloses an anti-electromagnetic interference laparoscope positioning device which comprises a sleeve and a laparoscope capable of being inserted into the sleeve, a reflector is fixedly installed at the end, close to the operation end of the laparoscope, of the sleeve, and scales are arranged on the surface of the sleeve and used for reading the distance from a wound to the reflector; a distance sensor is installed at the operation end of the laparoscope and used for transmitting a detection signal to the reflector and receiving a reflection signal of the reflector so as to obtain the distance from the distance sensor to the reflector; an AHRS sensor is further installed at the operation end of the laparoscope and used for outputting attitude data. A processing unit is mounted at the operation end of the laparoscope; according to the invention, the drift error of the existing inertial sensor caused by electromagnetic interference is effectively eliminated, and the surgical risk is reduced; the problem of depth distortion caused by magnetic field disturbance and drift error integration is fundamentally avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laparoscopic tracking positioning, and more particularly, to an anti-electromagnetic interference laparoscopic positioning device and an anti-electromagnetic interference laparoscopic positioning method. BACKGROUND

[0002] As a core technology of minimally invasive surgery, laparoscopic surgery establishes a small incision on the surface of the patient's body, introduces a long laparoscope and operating instrument into the body cavity through a cannula channel, and completes diagnosis and treatment with the help of an endoscopic imaging system. Its core advantage is small trauma and fast recovery, but precise positioning is always a technical difficulty - especially in complex anatomical regions, the three-dimensional position of the laparoscope tip directly affects the safety and efficiency of the operation.

[0003] Currently, the laparoscopic system mainly realizes laparoscopic depth perception by integrating inertial sensors. Such sensors are usually installed on the handle of the laparoscope operating end, and fuse three-axis accelerometer, gyroscope and magnetometer data to calculate the relative displacement of the laparoscope in the abdominal cavity in real time according to the kinematic model. For example, after initial pose calibration, the depth change is derived by using acceleration quadratic integration or direction cosine matrix transformation. This scheme can theoretically realize dynamic tracking and does not require external auxiliary equipment.

[0004] The existing laparoscopic depth positioning technology based on inertial sensors has an essential defect in the high-frequency electrocautery, metal instruments and other multi-source strong electromagnetic interference environment in the operating room: the magnetic force meter is disturbed by ferromagnetic substances, causing the direction reference to drift, the accelerometer signal is covered by high-frequency noise, there is drift error, which causes the distortion of the three-dimensional coordinate values calculated by integral fitting; lack of absolute depth reference, unable to eliminate cumulative error online, the actual positioning error can reach centimeter level, and quickly accumulates with time, which easily causes surgical risks in complex anatomical regions. SUMMARY

[0005] The present application aims to overcome the above-mentioned defects of the prior art and provide an anti-electromagnetic interference laparoscopic positioning device to solve the technical problems of lack of absolute depth reference, inability to eliminate cumulative error online, and easy to cause surgical risks in complex anatomical regions.

[0006] The technical scheme adopted by the present application is a laparoscope positioning device with anti-electromagnetic interference, comprising a sleeve and a laparoscope which can be inserted into the sleeve, a reflector is fixedly installed at the end of the sleeve close to the operation end of the laparoscope, a scale is arranged on the surface of the sleeve for reading the distance from the wound to the reflector, a distance sensor is installed at the operation end of the laparoscope for emitting a detection signal to the reflector and receiving a reflected signal thereof to obtain the distance from the distance sensor to the reflector, an AHRS sensor is also installed at the operation end of the laparoscope for outputting attitude data, and a processing unit is installed at the operation end of the laparoscope and configured to calculate the insertion depth of the laparoscope as a depth reference value according to the distance from the wound to the reflector and the measurement value of the distance sensor, and perform data fusion on the attitude data output by the AHRS sensor based on the depth reference value to output the three-dimensional coordinates of the tip of the laparoscope.

[0007] The ranging mechanism of emitting an optical detection signal to the reflector fixed on the sleeve by the distance sensor and receiving the reflected signal thereof directly obtains an absolute insertion depth physical quantity which is not polluted by electromagnetic noise, has no drift error and is absolute. This establishes a stable and reliable absolute depth reference for the whole system, so that the absolute depth reference can be used to fuse the AHRS sensor data to output the actual three-dimensional coordinates of the tip of the laparoscope, effectively suppresses the cumulative error and reduces the risk of surgery caused by inaccurate positioning.

[0008] Further, the reflector is in the form of a ring and is coaxially fixed to the outer surface of the sleeve close to the operation end of the laparoscope.

[0009] Further, the insertion depth of the laparoscope is calculated by the following formula = - - ; Wherein: : the distance from the installation position of the distance sensor to the tip of the laparoscope; : the distance between the distance sensor and the reflector measured in real time; : the distance from the wound to the reflector when the sleeve is fixed to the wound.

[0010] Further, the distance sensor is an infrared ranging sensor or a laser ToF sensor, and the measurement range is 4-30 cm.

[0011] Further, the processing unit fuses the insertion depth value of the laparoscope with the Euler angle data of the AHRS sensor to obtain the three-dimensional coordinate position of the tip of the laparoscope in the established walking orientation coordinate system, and the origin of the walking orientation coordinate system is the intersection of the central axis of the sleeve (1) and the body surface.

[0012] Furthermore, the processing unit is provided with an outlier filter; the outlier filter is configured to detect outliers by comparing the sign changes between adjacent sampled values ​​of the measurement data, and replace the detected outliers with the previous valid sampled value.

[0013] Furthermore, the operating end of the laparoscope integrates a handle, which includes: The main frame is fixed to the operating end of the laparoscopy and has a compartment for accommodating the distance sensor. The fixed shell is connected to the main frame by bolts, together forming a compartment for accommodating the processing unit; The battery cover is detachably installed at the battery compartment opening of the main frame.

[0014] An electromagnetic interference-resistant laparoscopic positioning method, based on the aforementioned electromagnetic interference-resistant laparoscopic positioning device, includes the following steps: S1, the distance measured from the distance sensor to the tip of the laparoscope. ; S2. Fix the cannula to the wound and obtain the distance from the wound to the reflector through the scale on the outer circumference of the cannula. The distance to the reflector is measured in real time by a distance sensor. ; S3, through formula = - - Calculate the actual insertion depth of the laparoscopy ; S4. Combining the attitude angle data from the AHRS sensor, calculate the three-dimensional coordinates of the laparoscopic tip using the projection method or the transformation matrix method.

[0015] Furthermore, the projection method described in step S4 specifically includes: S4a. Obtain the Euler angles measured in real time by the AHRS sensor: pitch angle θ, roll angle φ, and yaw angle after transformation from the body coordinate system to the wandering azimuth coordinate system. (because It is the angle of clockwise rotation, so here <0); S4b. Establish a wandering orientation coordinate system. The origin of the wandering orientation coordinate system is the intersection of the central axis of the cannula and the surface plane. The three coordinate axes of the wandering orientation coordinate system are defined as follows: the projection of the laparoscope onto the horizontal plane when it first enters the working area is X. W The axis is Z, and the direction of gravitational acceleration is Z. W The axis is determined, and Y is determined according to the right-hand rule. W axis; S4c, Ignore the roll angle φ (rotation around the laparoscope axis, which has no effect on the insertion depth), and obtain the actual insertion depth. Projected to X W Y W Plane, then decompose the projection components to X W Axis, Y W axis; The calculation formula is as follows: ,

[0016] Z W Directional coordinate position: Z is determined by a single projection. W Axis coordinates; The calculation formula is as follows: .

[0017] Furthermore, the transformation matrix method described in step S4 achieves the transformation from the volume coordinate system to the wandering azimuth coordinate system using the following matrix: S41. Obtain the Euler angles measured in real time by the AHRS sensor: pitch angle θ, roll angle φ, and yaw angle after transformation from the body coordinate system to the wandering azimuth coordinate system. (because It is the angle of clockwise rotation, so here <0); S42. Establish a wandering orientation coordinate system. The origin of the wandering orientation coordinate system coincides with the intersection of the central axis of the cannula and the surface plane it passes through. The three coordinate axes of the wandering orientation coordinate system are defined as follows: X is the projection on the horizontal plane when the laparoscopy first enters the working area. W The axis is Z, and the direction of gravitational acceleration is Z. W The axis is determined, and Y is determined according to the right-hand rule. W axis; S43. Based on the Euler angles obtained in step S41, construct the attitude transformation matrix from the volume coordinate system to the wandering orientation coordinate system.

[0018] S44. Represent the coordinates of the laparoscopic tip position in the body coordinate system. With transformation matrix Multiply them and calculate their coordinates in the wandering azimuth coordinate system, that is Expand your writing:

[0019] The coordinates The values ​​of the last two components are 0, that is... , where is the coordinate of the position of the laparoscope tip in the body coordinate system. A value of zero indicates that the offset of the laparoscopic tip in the Y and Z axes of the body coordinate system is zero. The reason is as follows: since the X-axis of the body coordinate system coincides with the axis of the laparoscopy, the X-axis value in the body coordinate system is related to the insertion depth. Correspondingly, the values ​​of the Y-axis and Z-axis are zero.

[0020] The calculation results are as follows =

[0021] Among them, the yaw angle after transformation from the body coordinate system to the wandering azimuth coordinate system The wander angle α represents the angle between the X-axis of the navigation coordinate system (n-frame) and the X-axis of the wandering azimuth coordinate system (w-frame). This represents the uncalibrated raw yaw angle measured by the AHRS sensor in the navigation coordinate system (n-frame).

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: By employing a ranging mechanism that transmits optical detection signals to a reflector fixed on the cannula via a distance sensor and receives the reflected signals, an absolute physical quantity of insertion depth, free from electromagnetic noise contamination and drift error, is directly obtained. This establishes a stable and reliable absolute depth benchmark for the entire system. Based on this depth benchmark, combined with the attitude angle data from the AHRS sensor, the three-dimensional coordinates of the laparoscopic tip are calculated. This effectively eliminates the drift error caused by electromagnetic interference in existing inertial sensors, reducing surgical risks. It also fundamentally avoids the depth distortion problem caused by magnetic field disturbances and drift error integration, with a measured error ≤1.5cm. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0024] Figure 2 This is a schematic diagram of the structure of the distance sensor, AHRS sensor, Arduino microcontroller, and WiFi expansion board after installation.

[0025] Figure 3 This is a schematic diagram of the assembly of the laparoscope, cannula, reflector, and outer casing handle of the present invention.

[0026] Figure 4 This is a schematic diagram of the laparoscopic motion trajectory and filtering effect of the present invention.

[0027] Figure 5 : This is a comparison chart of the detection results from the Falcon system and the detection results from this invention.

[0028] Figure 6: This is a comparison chart of the detection results from the EMT system and the detection results from this invention.

[0029] Figure 7 : This is a diagram of the experimental setup used for performance evaluation of this invention via Falcon.

[0030] Figure 8 This is a schematic diagram of the adapter in the performance evaluation experimental device using Falcon according to the present invention.

[0031] Figure 9 This is a schematic diagram of the bearing structure in the performance evaluation experimental device using Falcon according to the present invention.

[0032] In the diagram: 1. Tube; 2. Laparoscope; 3. Reflector; 4. Distance sensor; 5. Processing unit; 6. Main frame; 7. Fixing shell; 8. Battery cover; 9. Mounting platform. Detailed Implementation

[0033] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the invention. To better illustrate the following embodiments, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions; it is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0034] like Figures 1-7 As shown, this solution discloses a laparoscopic positioning device that resists electromagnetic interference. Specifically, the device includes a cannula 1, a laparoscope 2, a reflector 3, a distance sensor 4, and a processing unit 5, with each component working in concert.

[0035] Cannula 1 and reflector 3. During the surgical procedure, cannula 1 is first inserted into and secured to the patient's wound to protect the wound and provide access for the laparoscope 2. At this time, the position of cannula 1 remains stable at the wound. According to an improvement of the invention, a reflector 3 is fixedly mounted on the exposed portion of cannula 1 (i.e., the end located outside the patient's body, closer to the operator), and the reflector 3 is securely attached to cannula 1. Scales are drawn on the outer wall of cannula 1 for accurately reading the distance from the wound to the reflecting surface of reflector 3.

[0036] like Figure 3 As shown, reflector 3 is composed of [specific components]. To achieve better reflection, a detachable and fixed connection between the disc and sleeve 1 is adopted. This design must ensure that the installation of the disc does not affect the normal function of sleeve 1. Simultaneously, it must be ensured that there are no obstructions between reflector 3 and distance sensor 4. Therefore, reflector 3 is installed at the end of sleeve 1. Reflector 3 and sleeve 1 are mechanically connected through a split cylindrical housing, where the left half of the housing is integrally formed with the disc, and the two cylindrical housings are fastened together using M2.2 bolts.

[0037] like Figure 2 As shown, a laparoscope 2 and a distance sensor 4 are present. The laparoscope 2 is inserted into a cannula 1 and moves axially along the cannula 1 during operation. Its working end includes components such as an imaging system and a cold light source. According to the present invention, a distance sensor 4 is installed at the rear end of the laparoscope 2. Preferably, a Sharp GP2YOA41SK0F infrared distance sensor is used. This sensor emits a modulated infrared beam to a reflector 3 and receives the infrared light signal returned by the surface of the reflector 3. Based on the principle of time-of-flight of light or the principle of triangulation, it accurately calculates the real-time distance between the distance sensor 4 and the reflector 3 (i.e., as shown in the diagram). Figure 1 shown The sensor has an effective measurement range of 4 cm to 30 cm and excellent electromagnetic interference resistance. Alternatively, the distance sensor 4 can also be other types of optical non-contact distance sensors (such as laser ToF sensors), as long as the distance measurement requirement is met.

[0038] In the integrated implementation, an AHRS (Attitude and Heading Reference System) sensor is also installed at the rear end of the laparoscope 2. This sensor includes a three-axis accelerometer, a three-axis gyroscope, and a three-axis magnetometer, which can output the spatial attitude and motion acceleration data of the laparoscope 2 in real time.

[0039] Processing unit 5 includes an Arduino microcontroller and a WiFi expansion board. For example... Figure 3 As shown, a dedicated bracket was designed to compactly mount the distance sensor 4 and all related components (such as the WiFi expansion board and battery) onto the laparoscope 2. Due to the large size of the Arduino microcontroller and WiFi expansion board, a handle structure was designed at the end of the laparoscope 2. This design does not interfere with user operation and ensures an ergonomic user experience. The handle consists of three parts: a main frame 6, a mounting shell 7, and a battery cover 8. The main frame 6 is the core of the handle, containing two independent compartments for housing the Arduino processing unit and the distance sensor 4, respectively. The larger compartment is 54.5 mm wide and 104 mm long, with a battery replacement port at the rear. The smaller front compartment is used to secure the distance sensor 4; its frame both secures the distance sensor 4 and effectively protects it from damage. A cable channel is provided at the bottom of the frame for connecting the signal from the distance sensor 4 to the processing unit. The mounting shell 7 is 16 mm wide, ensuring it does not completely obstruct the WiFi expansion board and providing sufficient space for cable connections. All components have a wall thickness of 1.5 mm and are secured together using M3 bolts. All parts of the handle are made of polylactic acid (PLA) material and 3D printed.

[0040] Electrical Coupling: The AHRS sensor is the Adafruit BNO055, a 9-axis sensor. Raw data is processed by the integrated microcontroller before output. Output values ​​are transmitted via the I2C bus; data signals are transmitted via the SDA line, and clock signals via the SCL line. During wiring, the SDA and SCL pins are connected to the WiFi board. The BNO055 sensor operates on a power supply voltage of 3.3 to 5.0 volts. The distance sensor 4 has an input voltage of 5 volts. Output values ​​are provided as analog signals. Therefore, its signal lines are connected to the analog signal pins of the processing unit. The microcontroller used is an Arduino Mega 2560. It can be powered via a USB port or an external power source such as a battery. The external power supply voltage can vary between 7 and 12 volts. A 9-volt battery was used in this setup. The Arduino WiFi board connects directly to the Arduino Mega board via a header, enabling the microcontroller to communicate with the computer using the wireless WiFi standard (IEEE 802.11).

[0041] To obtain the actual insertion depth of the laparoscope 2 within the abdominal cavity (i.e., the depth to which the working end enters the abdominal cavity), Figure 1 In This embodiment provides a direct and interference-resistant measurement method for the actual insertion depth of the laparoscopy 2. Equal to laparoscopic 2 fixed length Value (distance sensor 4 is installed at the base of laparoscope 2, therefore) (The length of the entire laparoscope tube 2 is a known constant) minus the distance sensor 4 obtained from the reflector 3. The value is then subtracted from the inherent dimension of the cannula 1 extending outside the abdominal cavity (i.e., (Value). The value represents the axial distance from the fixation point of the wound (i.e., the physiological reference point for depth) to the reflective surface of the reflector 3 on the cannula 1 when the cannula 1 is fixed to the wound. This is a known dimensional parameter determined by the physical structure of the cannula 1. This dimension can be read directly from the scale on the outside of the cannula 1. It is obtained through the formula ( = - - The actual insertion depth calculated Its principle is based on direct signal measurement, which is not affected by environmental magnetic fields or metal interference.

[0042] Operating steps: A laparoscopic positioning method, implemented based on the aforementioned device, includes: S1, Measuring the distance from distance sensor 4 to the tip of laparoscope 2 ; S2. Fix the cannula 1 at the wound, and obtain the distance from the wound to the reflector 3 through the scale on the outer circumference of the cannula 1. The distance sensor 4 measures the distance to the reflector 3 in real time. ; S3, Based on Formula = - - Calculate and output the actual insertion depth of laparoscope 2; S4. Combining the attitude angle data from the AHRS sensor, calculate the three-dimensional coordinates of the tip of the laparoscope 2 using the projection method or the transformation matrix method.

[0043] Sensor data fusion: The Euler angles output by the AHRS sensors describe the attitude of the volume coordinate system (b-frame) relative to the navigation coordinate system (n-frame). Since the navigation coordinate system is often not suitable for local spatial positioning, the attitude needs to be transformed to the wandering orientation coordinate system (w-frame).

[0044] The body coordinate system (b-frame) is a coordinate system that moves with the laparoscope, and its origin is usually located at the center of gravity of the object. In this invention, an AHRS sensor is used, the origin of the body coordinate system coincides with the center of the AHRS sensor, the X-axis coincides with the axis of the laparoscope, and the Y-axis and Z-axis are perpendicular to the axis according to the right-hand rule.

[0045] Navigation coordinate system (n-frame): When the sensor is close to the Earth's surface, a navigation coordinate system is used. The origin of this coordinate system coincides with the origin of the volume coordinate system, and the X-axis and Y-axis point north and east, respectively. The resulting plane is parallel to the Earth's surface. According to the right-hand rule, the Z-axis in this coordinate system points vertically downwards and aligns with the direction of gravitational acceleration; therefore, this coordinate system is also called the North-East-Earth coordinate system.

[0046] The wandering azimuth coordinate system (w-frame) is a fixed coordinate system based on the navigation coordinate system. Its XY plane is parallel to the Earth's tangent plane (i.e., the horizontal plane), and its Z-axis is along the direction of the Earth's gravitational acceleration. Compared to the navigation coordinate system, the wandering azimuth coordinate system can rotate around the Z-axis (i.e., "azimuth wandering"), and its X-axis does not point north, which can be defined according to the actual scenario. The wandering angle α represents the angle between the X-axis of the navigation coordinate system and the X-axis of the wandering azimuth coordinate system. In this invention, the origin of the wandering azimuth coordinate system coincides with the cannula puncture point (i.e., the intersection of the central axis of the cannula and the surface plane it passes through), serving as the reference coordinate system of this invention. The direction of the projection of the laparoscopy's axis onto the horizontal plane when it first enters the working area can be defined as the X-axis, and then the Y-axis direction can be determined according to the right-hand rule.

[0047] By using the yaw angle in the navigation coordinate system Subtract the wandering angle It can calculate the yaw angle under w-frame. :

[0048] The position of the tip of the laparoscopy blade can be calculated using any of the following methods: Projection Method: Due to the unique operational characteristics of laparoscopy, its motion can be decomposed into translational motion along the X-axis and rotational motion around the Z and Y axes. The position of the laparoscope tip 2 can be determined by projecting the insertion length onto the corresponding coordinate axes. Since the Euler angles in the AHRS sensor are expressed in the form of a ZYX rotation sequence, it should be noted that the projection calculation must be performed in reverse order. Because the roll angle φ is the rotation angle around the laparoscope axis, it has no effect on the insertion depth and can be ignored when calculating X... W Y W When determining the position coordinates of the axis, first... Projected to X W Y W Plane, then decompose the projection components to X W Y W Axis. The calculation formula is as follows: , Z W The coordinates can be determined directly through a single projection. The calculation formula is as follows: .

[0049] This method employs a more intuitive geometric projection approach. It first determines the insertion depth of the laparoscope 2. Treat it as a spatial vector, and then based on the pitch angle and yaw angle The vector is decomposed sequentially onto the axes of the wandering azimuth coordinate system, thus directly obtaining the coordinates of the tip. The roll angle φ is ignored because the rotation of the laparoscope around its own axis does not change the position of its tip in space; this simplifies the calculation and conforms to actual physical meaning.

[0050] Transformation Matrix Method: Another method for position calculation is using a transformation matrix. The transformation matrix shows the relationship between the volume coordinate system (original coordinate system) and the wandering orientation coordinate system (target coordinate system), and its formula is as follows: Attitude Transformation Matrix

[0051] Since the X-axis of the body coordinate system coincides with the axis of the laparoscope 2, the coordinates of the tip of the laparoscope 2 are... X-axis coordinate values ​​and insertion depth Correspondingly, the values ​​of the Y-axis and Z-axis are both zero, that is... By converting it to a wandering coordinate system using the following method, the position of the tip of the laparoscope 2 can be calculated, and the result after unfolding is consistent with that of the projection method.

[0052]

[0053]

[0054] This method is a more general and rigorous mathematical tool. The attitude transformation matrix... The overall measurement includes pitch angle. Roll angle φ and yaw angle All rotation information. This is achieved by using the tip position coordinates in the volume coordinate system. = Multiplying by this matrix allows for a one-step coordinate transformation. Although the formula is complex, the calculation results are consistent with those of the projection method, verifying the correctness of the algorithm.

[0055] Using any of the methods described above, the system can ultimately output the three-dimensional coordinates of the laparoscopic tip in a fixed wandering orientation coordinate system. This achieves high-precision, interference-resistant positioning.

[0056] The raw output data from distance sensor 4 needs to be smoothed to eliminate outliers: Filtering Method: Since the distance sensor 4 generates outliers in the measurement data (usually caused by random high-frequency noise), a filter is needed. This design compares three different filters. Low-pass filters are among the most commonly used noise filters in digital signal processing. Because noise typically occurs in the high-frequency range and overlays the signal, low-pass filters can reduce noise by removing signals above the cutoff frequency. Figure 4 In this example, a fourth-order Butterworth low-pass filter was used with a cutoff frequency of 10Hz. However, its smoothing effect was not ideal, and outliers still existed. The second filter can be considered as a buffer, filled with three adjacent sampled values. During this process, the difference between two adjacent values ​​is compared. If they have different signs, a peak or outlier exists. Outliers can be eliminated by replacing the current value with the last error-free value, see [link to documentation]. Figure 4 The middle chart shows that while most outliers were filtered out, some could not be eliminated by the filter. Expanding the buffer to five samples yielded the best filtering effect. Although this filter has a slightly larger time delay than the previous two, the impact is minimal for routine laparoscopic procedures; therefore, a five-sample buffer filter was used in this study.

[0057] Prototype implementation and assembly: Handle installation: After all parts are manufactured, all parts should be assembled and the distance sensor 4 should be placed into the housing. Figure 2 and 3A schematic diagram showing the assembled prototype and the handle without electronic components installed.

[0058] AHRS Sensor Installation: In clinical practice, the end of the laparoscope 2 is typically held during operation. It is essential to ensure the threaded interface of the fiber optic cable is facing upwards and that the 30° optical lens is always aligned with the target organ. Considering the AHRS sensor is used for orientation measurement, its installation cannot be arbitrarily oriented; it must be rigidly connected and kept parallel to the laparoscope 2. Simultaneously, the side of the sensor circuit board with the chip should face upwards. To meet these requirements, a mounting platform 9 was designed. The mounting platform 9 has 3mm thick supporting walls on both sides and is fixedly connected to the main frame 6 using M3 standard screws. The front of the mounting platform 9 has a 14.5mm inner diameter hole, allowing the fiber optic interface of the laparoscope 2 to pass vertically. An interference fit ensures a tight fit between the mounting platform 9 and the lower part of the fiber optic interface, restricting the translational movement of this component relative to the laparoscope 2 in the XY plane. Two symmetrical rectangular openings, 16mm long and 8mm wide, are located at the waist of the mounting platform 9 for the AHRS sensor pins and connecting wires to pass through. The AHRS sensor circuit board has built-in mounting holes and is secured to the mounting platform 9 using four M2.2 bolts.

[0059] Operating Procedure: First, cannula 1 is inserted into the patient's wound and fixed in place, while reflector 3 remains static. Laparoscope 2 is inserted into cannula 1, and distance sensor 4 measures the distance in real time. The processing unit outputs three-dimensional coordinate values ​​based on a formula.

[0060] Experimental verification and performance evaluation: The positioning accuracy of the developed electromagnetic interference-resistant laparoscopic positioning system was analyzed and evaluated using two different reference systems: Novint's Falcon 3D controller and Northern Digital's Aurora electromagnetic tracking system.

[0061] The first method: Figure 7The demonstration shows an evaluation setup using the Falcon as a reference system. The Novint Falcon was originally developed for computer games. Due to its ease of operation and high positioning accuracy, this system is well-suited for use as an evaluation platform. In its implementation, a right-angled support is first constructed, and the Falcon is mounted at a 45° angle. An adapter connects the tip of the Falcon to the tip of the laparoscope 2 (replacing a traditional game controller), allowing the Falcon to accurately measure its tip position. This adapter features a specially designed universal joint structure, ensuring the laparoscope can move freely during measurement to simulate surgical movements. It is crucial that the orthogonally intersecting journals of the universal joint are in the same plane; otherwise, the measurement data will deviate from the actual position of the laparoscope 2 tip. The miniature sleeve connecting the universal joint and the laparoscope is 3D printed, achieving a rigid connection between the laparoscope and the upper part of the universal joint through an interference fit. Figure 8 The specific structure of the laparoscopic adapter is shown.

[0062] To simulate surgical incisions on a patient, a design was created. Figure 9 The bearing structure features a U-shaped bracket bolted to a right-angled support, inside which is a rotatable square frame. This frame contains a 30mm diameter cylinder whose axis of rotation is staggered by 90° from the axis of rotation of the square frame. This structure enables three-axis rotation. A laparoscopic guide assembly is fixed within the cylinder via an interference fit. This assembly consists of a cube with a 12mm through-hole (forming a clearance fit with a 10mm diameter laparoscope) and a circular disc serving as an infrared reflector.

[0063] The Falcon device's three-segment extendable robotic arm and its joint system create a three-dimensional motion space, allowing its end effector to reach any spatial position within its range of motion. Through its built-in software, Falcon can precisely position the end effector and provide the force required for position locking as needed. Its positioning resolution reaches 400 dpi (dots per inch), meaning sub-millimeter level positioning accuracy is achievable.

[0064] During the measurement process, the tip of laparoscope 2 is simultaneously tracked by both an electromagnetic interference-resistant laparoscope positioning device and a Falcon device. The orientation of the Falcon coordinate system is as follows: Figure 7 As shown: the Z-axis is tilted upwards at 45° and parallel to the longitudinal axis of the equipment, while the X-axis serves as the transverse axis pointing inwards. According to the right-hand rule, the Y-axis is perpendicular to the XZ plane and points to the upper left. The coordinate data of the electromagnetic interference-resistant laparoscopic positioning device are represented in a wandering coordinate system (w-frame), whose origin coincides with the rotation pivot point of the bearing structure.

[0065] To compare measurement data, it is necessary to transform the positional information measured in one coordinate system to another. The simplest transformation method is to simultaneously collect a series of corresponding points in both coordinate systems and calculate the transformation matrix between the systems. For example, using the Horn quaternion method, the rotation matrix, translation matrix, and scaling factor can be calculated using measurements from at least three points in both systems. The more points available, the higher the quality of the results. This method is based on the least squares principle, and its analytical solution ensures high-speed computation.

[0066] In practice, before comparing the data, the laparoscope is moved freely for 10 seconds, and position data is recorded synchronously at a sampling frequency of 40Hz. The transformation matrix is ​​then calculated based on this data. After the coordinate system transformation is completed, the two coordinate systems coincide, and the measurement data become comparable.

[0067] Data acquisition and processing were implemented using LabVIEW. Since the sampling times of the two systems are synchronized, the measurement data are always time-aligned and can be directly compared. Theoretically, a higher sampling frequency results in higher measurement accuracy. In this system, the period of the two systems was set to 25ms, i.e., the sampling frequency was 40Hz. The sampled data was subsequently analyzed using Matlab.

[0068] The advantage of the Falcon assessment system lies in its ability to directly detect the mechanical movements of the laparoscope through the device. There is no interaction between the two measurement systems; the measurements are independent and the correlation between the systems is clearly presented. However, its limitations are also apparent: because the Falcon's range of motion is mechanically limited, it cannot track points beyond that range, thus making it difficult to fully simulate real surgical scenarios.

[0069] The second method utilizes electromagnetic tracking (EMT), a widely used positioning technology in the medical field (a technology well-known to those skilled in the art, and only briefly described below), which serves as the core reference system in this study. The system comprises three main components: a magnetic field generator that uses multi-frequency current to generate an alternating magnetic field in a coil, establishing a 500×500×500mm³ three-dimensional electromagnetic environment with a known spatial field strength distribution as the effective tracking space; a 6DOF sensor coil fixed to the tip of the laparoscope 2, inducing current within the electromagnetic field; and a controller that analyzes these signal strengths and, using a known field model, deduces the relative position and angle of the sensors, ultimately outputting 6DOF data, namely the position coordinates (X, Y, Z) and rotation angles (Pitch, Yaw, Roll) of each sensor relative to the magnetic field generator. Its positioning principle is based on utilizing the known geometric properties of a non-uniform magnetic field, determining the spatial position of the sensors by measuring the magnetic field components to achieve millimeter-level positioning accuracy (measured ≤1.5mm).

[0070] To simulate real surgical scenarios, this system is deeply integrated with the ELITE (Endoscopic-Laparoscopic Interdisciplinary Training Unit) surgical model: the ELITE model accurately reproduces the anatomical structure of the human abdominal cavity, supporting clinical procedures such as cholecystectomy. The EMT system's unrestricted line-of-sight characteristics (electromagnetic fields can penetrate tissues to avoid optical obstructions) and dynamic tracking range of 500×500×500mm³ provide a realistic environmental basis for the verification of the anti-magnetic interference laparoscopic positioning system. This is a technology well-known to those skilled in the art and will not be described in detail here.

[0071] Test results: For example, Figure 4 This demonstrates a combined motion, which is generated along X. W Translational motion of the axis and motion around Z W Y W The rotational motion of the axis is combined to simulate the motion process during actual laparoscopic surgery. Figure 4 The top, middle, and bottom three figures show the changes in distance sensor measurements, yaw angle, and pitch angle during the motion process, respectively. Figure 5 The positional measurements of two measurement systems (Falcon system and anti-magnetic interference laparoscopic positioning system) during this movement were compared. Data analysis revealed a maximum measurement deviation of 1.33 cm, occurring at the Y-axis. W On the axis, at time t=8.57 seconds. Figure 6 The image shows the corresponding positional measurement records of two measurement systems (EMT system and anti-magnetic interference laparoscopic positioning system) during the movement. The human-simulated abdominal cavity space structure of ELITE determines the distance during this movement. The yaw angle has a larger range of motion, while the pitch angle has a smaller range of motion. In this measurement, the maximum difference between the two tracking systems was 1.47 cm, occurring in the Y... W On the axis, at time t=25.44 seconds.

[0072] The table below shows the tracking quality of the anti-magnetic interference laparoscopic positioning system after five typical laparoscopic motion tests (using EMT as the baseline). Compared to the other two axes, Y... W The overall measurement error for each axis is relatively large. This is clearly evident from the root mean square error and the 95th percentile. The average measurement deviation for a single axis is between 0.4 and 0.6 cm, reaching a maximum of 1 cm in Euclidean space. Furthermore, in all measurement data of the anti-magnetic interference laparoscopic positioning system, 95% of the data fall within a range of a maximum Euclidean distance of 1.5 cm from the reference value. Although the coefficients of variation (CVs) for the three axes are relatively large, the measurements exhibit good repeatability, with a CV of 8% for spatial observations.

[0073]

[0074] The core advantages of this device: Compared with the prior art, the beneficial effects of the present invention are: through algorithmic... The value serves as an absolute depth reference, which is fused with attitude data to output the actual inserted 3D coordinate position. This dual-sensor collaborative mechanism significantly improves the accuracy and robustness of the overall positioning system while retaining the advantages of the dynamic response of traditional inertial measurement.

[0075] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A laparoscopic positioning device resistant to electromagnetic interference, comprising a cannula (1) and a laparoscope (2) insertable therein, characterized in that: A reflector (3) is fixedly installed at the end of the cannula (1) near the operating end of the laparoscope (2). The surface of the cannula (1) is marked with a scale for reading the distance from the incision to the reflector (3). A distance sensor (4) is installed at the operating end of the laparoscope (2) for transmitting a detection signal to the reflector (3) and receiving its reflected signal to obtain the distance from the distance sensor (4) to the reflector (3). The operating end of the laparoscope (2) is also equipped with an AHRS sensor for outputting attitude data; The operating end of the laparoscope (2) is equipped with a processing unit (5), which is configured as follows: Based on the distance from the incision to the reflector (3) and the measurement value of the distance sensor (4), the insertion depth of the laparoscope (2) is calculated and used as the depth reference value; based on the depth reference value, data fusion is performed with the attitude data output by the AHRS sensor to output the three-dimensional coordinates of the tip of the laparoscope (2).

2. The laparoscopic positioning device against electromagnetic interference according to claim 1, characterized in that: The reflector (3) is a ring structure and is coaxially fixed to the outer circumferential surface of the cannula (1) near the operating end of the laparoscope (2).

3. The laparoscopic positioning device against electromagnetic interference according to claim 1, characterized in that: The insertion depth of the laparoscopy (2) is calculated using the following formula. = - - ; in: : The distance from the installation position of the distance sensor (4) to the tip of the laparoscope (2); The distance between the distance sensor (4) and the reflector (3) is measured in real time; : The distance from the wound to the reflector (3) when the cannula (1) is fixed to the wound.

4. The laparoscopic positioning device against electromagnetic interference according to claim 3, characterized in that: The distance sensor (4) is an infrared ranging sensor or a laser ToF sensor.

5. The laparoscopic positioning device against electromagnetic interference according to claim 3, characterized in that: The processing unit (5) inserts the laparoscope (2) to a depth value. By integrating the Euler angle data from the AHRS sensor, the three-dimensional coordinate position of the laparoscope (2) tip in the established wandering orientation coordinate system is obtained. The origin of the wandering orientation coordinate system is the intersection of the central axis of the cannula (1) and the body surface plane.

6. The laparoscopic positioning device against electromagnetic interference according to claim 3, characterized in that: An outlier filter is provided in the processing unit (5); The outlier filter is configured to detect outliers by comparing the sign changes between adjacent sampled values ​​of the measurement data, and to replace the detected outliers with the previous valid sampled value.

7. The laparoscopic positioning device against electromagnetic interference according to claim 3, characterized in that: The operating end of the laparoscope (2) is integrated with a handle, which includes: The main frame (6) is fixed to the operating end of the laparoscope (2) and has a compartment for accommodating the distance sensor (4); The fixed shell (7) is connected to the main frame (6) by bolts, together forming a compartment for accommodating the processing unit (5); The battery cover (8) is detachably installed on the battery compartment opening of the main frame (6).

8. A laparoscopic positioning method resistant to electromagnetic interference, based on the laparoscopic positioning device resistant to electromagnetic interference as described in any one of claims 3-7, characterized in that, Includes the following steps: S1, measuring the distance from the distance sensor (4) to the tip of the laparoscope (2). ; S2. Fix the cannula (1) at the wound, and obtain the distance from the wound to the reflector (3) through the scale on the outer circumference of the cannula (1). The distance between the distance sensor (4) and the reflector (3) is measured in real time. ; S3, through formula = - - Calculate the actual insertion depth of the laparoscopy (2) ; S4. Combine the attitude angle data of the AHRS sensor and calculate the three-dimensional coordinates of the tip of the laparoscope (2) by projection method or transformation matrix method.

9. The laparoscopic positioning method against electromagnetic interference according to claim 8, characterized in that: The projection method described in step S4 specifically includes: S4a. Obtain the Euler angles measured in real time by the AHRS sensor: pitch angle θ, roll angle φ, and yaw angle after transformation from the body coordinate system to the wandering azimuth coordinate system. ; S4b. Establish a wandering orientation coordinate system. The origin of the wandering orientation coordinate system is the intersection of the central axis of the cannula (1) and the surface plane. The three coordinate axes of the wandering orientation coordinate system are defined as follows: when the laparoscope (2) first enters the working area, the projection on the horizontal plane is X. W The axis is Z, and the direction of gravitational acceleration is Z. W The axis is determined, and Y is determined according to the right-hand rule. W axis; S4c, Ignore the roll angle φ, and obtain the actual insertion depth. Projected to X W Y W Plane, then decompose the projection components to X W Axis, Y W axis; The calculation formula is as follows: , Z W Directional coordinate position: Z is determined by a single projection. W Axis coordinates; The calculation formula is as follows: .

10. The laparoscopic positioning method against electromagnetic interference according to claim 8, characterized in that: In step S4, the transformation matrix method achieves the transformation from the volume coordinate system to the wandering azimuth coordinate system using the following matrix: S41. Obtain the Euler angles measured in real time by the AHRS sensor: pitch angle θ, roll angle φ, and yaw angle after transformation from the body coordinate system to the wandering azimuth coordinate system. ; S42. Establish a wandering orientation coordinate system. The origin of the wandering orientation coordinate system coincides with the intersection of the central axis of the cannula and the surface plane it passes through. The three coordinate axes of the wandering orientation coordinate system are defined as follows: when the laparoscope (2) first enters the working area, the projection on the horizontal plane is X. W The axis is Z, and the direction of gravitational acceleration is Z. W The axis is determined, and Y is determined according to the right-hand rule. W axis; S43. Based on the Euler angles obtained in step S41, construct the attitude transformation matrix from the volume coordinate system to the wandering orientation coordinate system. S44. Represent the coordinates of the laparoscope tip position in the body coordinate system. With transformation matrix Multiply them and calculate their coordinates in the wandering azimuth coordinate system. Since the axis of the laparoscopy (2) coincides with the X-axis of the body coordinate system, the coordinate... The values ​​of the last two components are 0, that is... , indicating that the offset of the laparoscope tip (2) in the Y-axis and Z-axis directions of the body coordinate system is zero; The calculation results are as follows = .

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