Disclosure of Invention
The invention aims to provide a dynamic tracking method and a dynamic tracking system based on a biplane X-ray system.
The invention provides a dynamic tracking method based on a biplane X-ray system, which comprises a transmitter and a receiver, wherein the transmitter is used for transmitting X-rays to a human body, the receiver is used for receiving the X-rays attenuated after passing through the human body to image, and the method comprises the following steps:
calibrating the spatial positions of the biplane X-ray system and tracking equipment;
acquiring the space position of the human joint through the tracking equipment;
Converting the joint position fed back by the tracking equipment into the coordinate of the biplane X-ray system through coordinates, and acquiring predicted joint position and joint speed information at the next moment to adjust the position of the biplane X-ray system so that the biplane X-ray system moves along with a joint;
and acquiring X-ray images and obtaining dynamic X-ray images of the joint motion of the human body, and obtaining the relative relation between joints under each frame through registration of the joint X-ray images of each frame and the three-dimensional model, thereby obtaining the kinematic parameters of the joints.
Preferably, the joint position and joint velocity information includes a joint center position and joint velocity in an X-Y-Z axis direction in the coordinate system of the biplane X-ray system, wherein the Z axis direction is a vertical direction, namely a transmission shaft direction, and the X-Y axis direction is a horizontal direction, namely a direction perpendicular to the Z axis.
Preferably, the acquiring the predicted next-time joint position and joint velocity information includes:
Obtaining the joint center state predicted value at the current moment by adopting a Kalman filterAccording to the state measurement value y (t) of the joint center space position and speed output at the current moment of the tracking equipment, correcting the joint center state predicted value at the current momentThereby obtaining an optimal estimateThe specific implementation is as follows:
wherein Q (t) is an input noise covariance matrix, and R (t) is an observed noise covariance matrix.
Ai is a constant;
the position estimate at time t is indicated,Representing a speed estimation value at the time t;
representing the position measurement at time t-1,Representing a speed measurement at time t-1;
The method comprises the steps of representing a state error at a moment t, representing a state transition matrix by F, representing a Kalman gain matrix by K, representing a state control matrix by B and representing a gain matrix by H.
Preferably, the calibrating the spatial position of the biplane X-ray system and the tracking device includes:
A correction box is arranged between the biplane X-ray system and the visual field of the tracking equipment instrument;
Capturing the space coordinates of a first marker on the correction box through the biplane X-ray system to output first coordinates;
capturing the space coordinates of the first marker on the correction box through the tracking equipment to output second coordinates;
And acquiring the spatial position of the first marker on the correction box, outputting a third coordinate, and acquiring a conversion matrix from the tracking equipment coordinate system to the biplane X-ray system coordinate system when the third coordinate corresponds to the first coordinate and the second coordinate.
Preferably, in the step of acquiring the spatial position of the human joint through the tracking device, if the tracking device adopts a photoelectric tracking device or an electromagnetic tracking device, a second marker is arranged at the joint part of the human body, and the spatial position of the human joint in a motion state is obtained by positioning the position of the human joint through the marker.
Preferably, in the acquiring the spatial position of the human joint by the tracking device, if the tracking device adopts a camera, the spatial position of the human joint in the field of view is automatically positioned by the camera, and the spatial position of the human joint in the motion state is obtained.
Preferably, the coordinate conversion of the joint position fed back by the tracking device to the coordinate of the biplane X-ray system, and the obtaining of the predicted joint position and joint velocity information at the next moment to adjust the position of the biplane X-ray system to enable the biplane X-ray system to follow the joint motion includes:
after the estimated joint position and joint speed are obtained, the joint position and joint speed are converted into the joint position and joint speed in the X-Y-Z three-axis direction under the coordinate system of the biplane X-ray system through coordinate transformation;
and sending the joint position and joint speed information in the X-Y-Z three-axis directions to a motor driver to control the movement of the transmitter and the receiver.
Preferably, the method for acquiring the predicted joint position and joint speed information at the next moment to adjust the position of the biplane X-ray system to enable the biplane X-ray system to move along the joint further comprises the steps of arranging a plurality of transmitters and a plurality of receivers in a way of being opposite to each other and on a transmission shaft, wherein the transmission shaft is arranged on a mobile platform, and a mobile platform motor driver drives the transmitters and the receivers to move along a plane according to the position and the speed components of an X-Y axis, and simultaneously controls the transmitters and the receivers to move along the Z axis according to the position and the speed components of the Z axis.
Preferably, the acquiring the predicted joint position and joint speed information at the next moment to adjust the position of the biplane X-ray system to enable the biplane X-ray system to move along with the joint further comprises arranging a plurality of transmitters and a plurality of receivers in opposite directions at the tail end of a mechanical arm, and driving the transmitters and the receivers to move freely by a mechanical arm motor driver according to the position and the speed components of an X-Y-Z axis.
The invention provides a dynamic tracking system based on a biplane X-ray system, which comprises a transmitter, a receiver and a dynamic tracking system, wherein the transmitter is used for transmitting X-rays to a human body, the receiver is used for receiving X-ray imaging after the X-rays pass through the human body, and the dynamic tracking system comprises:
the calibration module is used for calibrating the spatial positions of the biplane X-ray system and the tracking equipment;
The acquisition module is used for acquiring the space position of the human joint through the tracking equipment;
the coordinate conversion module is used for converting the joint position fed back by the tracking equipment into the coordinate of the biplane X-ray system through coordinates, and acquiring the predicted joint position and joint speed information at the next moment to adjust the position of the biplane X-ray system so that the biplane X-ray system moves along with the joint;
an adjustment module for adjusting the position of the biplane X-ray system according to the joint position and joint speed of the joint position prediction at the next moment so that the biplane X-ray system moves along with the joint;
The result output module is used for acquiring the X-ray images and obtaining dynamic X-ray images of the joint movement of the human body, and the relative relation between the joints under each frame is obtained through registration of the joint X-ray images of each frame and the three-dimensional model, so that the kinematic parameters of the joints are obtained.
Aiming at the prior art, the invention has the following beneficial effects:
According to the dynamic tracking method based on the biplane X-ray system, after joint position estimation, through space conversion of the biplane X-ray system and tracking equipment, position and speed information is sent to a motor driver through upper software, so that dynamic tracking of joints in the patient movement process is realized, and X-ray images of joint parts under the bearing position of the patient or the whole body positive side position of the patient are obtained;
the invention can obtain dynamic images in the process of joint movement, can obtain joint movement parameters under a complete natural action of a human body, and accurately evaluate the joint movement function of a patient;
The invention can obtain the space position of the center of the human joint in real time, can ensure that the center of the human joint is positioned at the center of the X-ray image at the positive/lateral position, and increases the duty ratio of useful information of the X-ray image in the whole X-ray image;
According to the invention, each frame of the acquired dynamic image is subjected to 2D-to-3D registration with the three-dimensional model, so that three-dimensional structure information and dynamic function information of bones and joints required by doctors are acquired.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
As shown in fig. 1, the dynamic tracking method based on a biplane X-ray system provided by the invention comprises a transmitter for transmitting X-rays to a human body, and a receiver for receiving the attenuated X-rays passing through the human body for imaging, and comprises the following steps:
step S1, calibrating the space positions of the biplane X-ray system and the tracking equipment;
s2, acquiring the space position of a human joint through the tracking equipment;
S3, converting the joint position fed back by the tracking equipment into the coordinate of the biplane X-ray system through coordinates, and acquiring predicted joint position and joint speed information at the next moment to adjust the position of the biplane X-ray system so that the biplane X-ray system moves along with the joint;
and S4, acquiring X-ray images and obtaining dynamic X-ray images of the joint movement of a human body, namely obtaining dynamic images in the joint movement process, and obtaining the relative relation between joints under each frame through registration of the joint X-ray images of each frame and the three-dimensional model, so as to obtain the kinematic parameters of the joints, and further analyze the movement function of a patient. The X-ray image acquired may be a patient's lower joint position or a whole body anterior/lateral X-ray image.
According to the dynamic tracking method based on the biplane X-ray system, after joint position estimation, through space conversion of the biplane X-ray system and tracking equipment, position and speed information is sent to a motor driver through upper software, dynamic tracking of patient movement is achieved, and X-ray images of joint parts under the bearing position or the whole body positive side position of the patient are obtained;
The invention can obtain dynamic images in the process of joint movement, can obtain joint movement parameters under a complete natural action of a human body, accurately evaluate the joint movement function of a patient, can obtain the center space position of the joint of the human body in real time, can ensure the center of the joint of the human body to be positioned at the center of an X-ray image at the positive/lateral position, increases the duty ratio of useful information of the X-ray image in the whole X-ray image, and carries out 2D-3D registration on each frame of the acquired dynamic image and a three-dimensional model, thereby obtaining the three-dimensional structure information and the dynamic function information of bones and joints required by doctors.
As shown in fig. 2, the calibrating the spatial position of the biplane X-ray system and the tracking device includes:
A correction box is arranged between the biplane X-ray system and the visual field of the tracking equipment;
Capturing the space coordinates of a first marker on the correction box through the biplane X-ray system to output first coordinates;
capturing the space coordinates of the first marker on the correction box through the tracking equipment to output second coordinates;
And acquiring the spatial position of the first marker on the correction box, outputting a third coordinate, and acquiring a conversion matrix from the tracking equipment coordinate system to the biplane X-ray system coordinate system when the third coordinate corresponds to the first coordinate and the second coordinate.
In this embodiment, the dual-plane X-ray system is adjusted to an initial position, the tracking device is fixed, the tracking device is shown in fig. 3, the patient is guaranteed to be in an imaging area of the tracking device, a correction box is placed in the visual field of the two devices, infrared reflective beads distributed in a known space are embedded on the surface of the correction box, the center of each reflective bead contains a metal steel ball, and the centers of the metal steel ball and the reflective beads are the same sphere, namely the first marker. Capturing the space coordinates of the spherical centers of the metal steel balls by using a biplane system, capturing the space coordinates of the reflecting small balls by using a tracking device, and correcting the space positions of the tracking device and the biplane X-ray system by using the space positions of all the reflecting small balls on the correction box, thereby obtaining a conversion matrix from the coordinate system of the tracking device to the coordinate system of the biplane X-ray system;
Specifically, in the step of acquiring the spatial position of the human joint through the tracking device, if the tracking device adopts photoelectric tracking device or electromagnetic tracking device, a second marker is arranged at the joint part of the human body, and the spatial position of the human joint in a motion state is obtained by positioning the position of the human joint through the marker. If optical tracking equipment such as photoelectric tracking is used, a reflective small ball, namely a second marker, needs to be arranged at the joint part of a patient, such as a hip joint, a knee joint and the like.
In particular, in the process of acquiring the space position of the human joint through the tracking device, if optical tracking devices such as photoelectric tracking and the like are used, reflective pellets are required to be installed on joint parts of a patient, such as hip joints, knee joints and the like, which need imaging. If the tracking equipment adopts a camera, the position of the human joint in the visual field is automatically positioned by the camera, and the spatial position of the human joint in a motion state is obtained. If a Kinect equal-depth camera is used, a marker is not required to be arranged at the joint position, the Kinect camera can automatically position the joint position of a human body in a visual field, a patient stands in an imaging area to finish a squatting-standing action, and in the movement process of the patient, the tracking equipment obtains the space position of the joint center under the self coordinate system, and the space position is converted into the coordinate system of the biplane X-ray system through a conversion matrix obtained by calibration in the step S1.
It can be understood by those skilled in the art that the tracking device obtains the spatial position of the joint center of the human body, the biplane X-ray system receives the joint center position fed back by the tracking device, predicts the joint center position and the joint movement speed at the next moment, adjusts the positions of the transmitter and the receiver to realize the following joint movement, and corrects the positions of the tracking device and the biplane system before the movement to obtain the relative position relation between the two. The tracking device comprises, but is not limited to, a camera, photoelectric tracking, electromagnetic tracking and the like, and after the three-dimensional coordinates of the joint center are obtained, the tracking device is transformed into the coordinates of a biplane X-ray system through the coordinates, and the biplane X-ray system adjusts the positions of the transmitter and the receiver according to the predicted information of the X-Y-Z three axes of the joint center position and the joint speed at the next moment, so that the dynamic tracking of the patient motion is realized.
To achieve coordinate transformation, the real-time spatial position p and velocity v of the center of the human joint can be regarded as a state function of time t
x(t)=(p(t),v(t))T,
Whereas the tracking device takes processing time to extract the transformed joint center coordinates, there is a time delay to follow the required spatial coordinates in real time relative to the biplane X-ray imaging system, thus based on the previous time-sequential joint center state optimal estimation
Obtaining the joint center state predicted value at the current moment by adopting a Kalman filterAccording to the state measurement value y (t) of the joint center space position and speed output at the current moment of the tracking equipment, correcting the joint center state predicted value at the current momentThereby obtaining an optimal estimateThe specific implementation is as follows:
wherein Q (t) is an input noise covariance matrix, and R (t) is an observed noise covariance matrix.
Ai is a constant;
the position estimate at time t is indicated,Representing a speed estimation value at the time t;
representing the position measurement at time t-1,Representing a speed measurement at time t-1;
the method comprises the steps of representing a state error at a moment t, representing a state transition matrix by F, representing a Kalman gain matrix by K, representing a state control matrix by B and representing a gain matrix by H.
Specifically, the joint position and joint speed information includes a joint center position and joint speed in an X-Y-Z axis direction in the coordinate system of the biplane X-ray system, wherein the Z axis direction is a vertical direction, namely a transmission shaft direction, and the X-Y axis direction is a horizontal direction, namely a direction perpendicular to the Z axis. In this embodiment, the spatial position of the center of the human joint is obtained in real time, so that the center of the human joint is located at the center of the positive side X-ray image, the duty ratio of useful information of the X-ray image in the whole X-ray image is increased, and the positive/side X-ray image can be obtained at other positions except the spatial position of the center of the human joint.
The step of converting the joint position fed back by the tracking device into the coordinate of the biplane X-ray system through coordinate transformation, and the step of obtaining the predicted joint position and joint speed information at the next moment to adjust the position of the biplane X-ray system so that the biplane X-ray system follows joint movement comprises the following steps:
after the estimated joint position and joint speed are obtained, the joint position and joint speed are converted into the joint position and joint speed in the X-Y-Z three-axis direction under the coordinate system of the biplane X-ray system through coordinate transformation;
The upper computer sends the information of the joint position and the joint speed in the X-Y-Z three-axis direction to the motor driver to control the movement of the transmitter and the receiver, so that the dynamic tracking of the movement of a patient is realized, and a tracking device and the driving closed-loop control are formed.
In one embodiment, the method for obtaining the predicted joint position and joint speed information at the next moment to adjust the position of the biplane X-ray system to enable the biplane X-ray system to move along the joint further comprises the steps of arranging a plurality of transmitters and a plurality of receivers in a relative mode on a transmission shaft, wherein the transmission shaft is arranged on a mobile platform, a mobile platform motor driver drives the transmitters and the receivers to move along a plane according to the position and the speed components of an X-Y axis, and meanwhile, the transmission shaft motor driver controls the transmitters and the receivers to move along the Z axis according to the position and the speed components of a Z axis, namely the transmission shaft direction, so that dynamic tracking of patient movement is achieved.
In one embodiment, the acquiring the predicted joint position and joint speed information at the next moment to adjust the position of the biplane X-ray system to enable the biplane X-ray system to move along with the joint further comprises arranging a plurality of transmitters and a plurality of receivers at the tail end of a mechanical arm in a relative mode, and driving the transmitters and the receivers to move freely by a mechanical arm motor driver according to the position and the speed components of an X-Y-Z axis, so that dynamic tracking of patient movement is achieved.
In order to track the position of any joint of a patient at any time to shoot an X-ray image and ensure the radiation range of the patient in the fields of view of an emitter and a receiver, a biplane X-ray system adopted in one embodiment of the invention is shown in figure 3, and a plurality of emitters and a plurality of receivers are oppositely arranged and arranged on a transmission shaft. The biplane X-ray system comprises at least one emitter and at least one receiver, namely the first emitter 4, the second emitter 3, the first receiver 1 and the second receiver 2 in the embodiment can be arranged on transmission shafts, the first emitter 4 is arranged on a fourth transmission shaft 14, the second emitter 3 is arranged on a second transmission shaft 12, the first receiver 1 is arranged on a first transmission shaft 11, the second receiver 2 is arranged on a third transmission shaft 13, and the first transmission shaft 11, the second transmission shaft 12, the third transmission shaft 13 and the fourth transmission shaft 14 are respectively arranged on a first moving platform 7, a second moving platform 8, a third moving platform 9 and a third moving platform 10, and the emitters and the receivers are driven by the moving platforms and the transmission shafts to move freely. In this embodiment, the dual-plane X-ray system emitter emits X-rays, the optical axes of the two emitters are 60-120 degrees, the dual-plane X-ray system receiver receives the X-rays attenuated by the human body and images the X-rays, the tracking device 5 is used for obtaining the joint center position of the joint to be tracked of the human body, and the upper computer 6 is used for converting the joint center coordinates obtained by the tracking device 5 into a dual-plane X-ray system coordinate system and controlling the motions of the dual-plane X-ray system emitter and the receiver.
That is to say the transmitter and the receiver are freely movable. One such way is that the transmitter and receiver may be mounted on a drive shaft that is mounted on a mobile platform, as shown in fig. 3. The transmitter and the receiver are driven by the mobile platform and the transmission shaft to move freely. The other way is that the emitter and the receiver are arranged at the tail end of the mechanical arm, and the mechanical arm drives the receiver and the emitter to move freely. The biplane X-ray system comprises two transmitters and two receivers, wherein any included angle between the two transmitters can be 60-120 degrees, and the transmitters emit X-rays and then image on the receivers through a human body. The transmitter and the receiver can move along a vertical axis or a horizontal axis or freely move, and during the movement, the receiver is ensured to be vertical to the optical axis of the transmitter at the moment when the optical axis intersects with the receiver and is positioned at the center of the receiver.
In this embodiment, an X-ray image is acquired and a dynamic X-ray image of a joint position is acquired during the completion of the motion, and a relative relationship between joints under each frame is obtained by registering the X-ray image of the joint and a three-dimensional model of each frame, so as to obtain a motion relationship between bones and joints, and the three-dimensional model can be realized by a three-dimensional reconstruction model and a statistical shape model of CT data of a patient, that is, a two-dimensional joint X-ray image is combined with the three-dimensional model to obtain a relative relationship between joints under each frame, so as to analyze a motion function of the patient.
Example two
The invention provides a dynamic tracking system based on a biplane X-ray system, which comprises a transmitter, a receiver and a dynamic tracking system, wherein the transmitter is used for transmitting X-rays to a human body, the receiver is used for receiving the X-rays attenuated after passing through the human body to image, and the dynamic tracking system comprises:
the calibration module is used for calibrating the spatial positions of the biplane X-ray system and the tracking equipment;
The acquisition module is used for acquiring the space position of the human joint through the tracking equipment and is not equal to the tracking equipment
The coordinate conversion module is used for converting the joint position fed back by the tracking equipment into the coordinate of the biplane X-ray system through coordinates;
an adjustment module for adjusting the position of the biplane X-ray system according to the joint position and joint speed of the joint position prediction at the next moment so that the biplane X-ray system moves along with the joint;
The result output module is used for acquiring the X-ray images and obtaining dynamic X-ray images of the joint movement of the human body, and the relative relation between the joints under each frame is obtained through registration of the joint X-ray images of each frame and the three-dimensional model, so that the kinematic parameters of the joints are obtained.
The invention can obtain dynamic images in the process of joint movement under the bearing position of a human body, can obtain joint movement parameters under the complete natural action of the human body, accurately evaluate the joint movement function of a patient, can obtain the central space position of the joint of the human body in real time, can ensure the center of the joint of the human body to be positioned at the center of an X-ray image at the positive/lateral position, increases the occupation ratio of useful information of the X-ray image in the whole X-ray image, and registers each frame of the acquired dynamic image with a three-dimensional model from 2D to 3D so as to acquire the three-dimensional structure information and the dynamic function information of bones and joints required by doctors.
The invention also provides a dynamic tracking device based on the biplane X-ray system, which comprises a memory and a processor, wherein the memory stores computer readable instructions, and the processor realizes the biplane X-ray method based on dynamic tracking in the first embodiment of the invention when executing the computer readable instructions.
The specific contents and implementation methods of the calibration module, the acquisition module, the coordinate conversion module, the adjustment module, and the result output module are as described in the first embodiment, and are not repeated here.
It should be noted that the above-mentioned embodiments are merely for illustrating the technical solution of the present invention, and not for limiting the same, and although the present invention has been described in detail with reference to the above-mentioned embodiments, it should be understood by those skilled in the art that the technical solution described in the above-mentioned embodiments may be modified or some technical features may be equivalently replaced, and these modifications or substitutions do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solution of the embodiments of the present invention.