Disclosure of Invention
The purpose of the invention is as follows: aiming at the defects, the invention provides a system precision verification device and method based on 2D-3D image registration, which are used for verifying whether the image registration precision reaches the technical standard or not and providing a data basis for subsequent precision correction and promotion.
The technical scheme is as follows:
a system accuracy verification apparatus, comprising:
the bearing body is provided with a tooling tracer and at least three co-planar non-collinear registration points;
at least one vertebral segment is provided with at least one simulation channel;
the verification piece is provided with two detection points corresponding to the simulation channel.
The simulation channel penetrates through the vertebral pedicle of the vertebral segment, and two channel points are arranged at two ends of the simulation channel.
The distance between the two channel points is 6-10 mm.
The channel points are steel balls with the diameter of 4 mm.
The vertebral segments comprise movable vertebral segments and fixed vertebral segments, the movable vertebral segments are arranged on the supporting body through a spherical hinge structure, the fixed vertebral segments are fixedly arranged on the supporting body, and the posture of a patient in the operation is simulated through adjusting the posture of the movable vertebral segments.
The verification piece is a probe and comprises a main body matched with the mechanical arm end effector and detection points arranged at two ends of the main body.
A disc matched with the mechanical arm end effector for axial limitation is arranged at one end of the probe main body; and the side surface of the disc is provided with a bulge matched with the mechanical arm end effector for circumferential limitation.
The detection point is a steel ball with the diameter of 6 mm.
The distance between the registration points is not less than 10 mm.
The registration points are steel balls with the diameter of 4 mm.
A system precision verification method comprises the following steps:
(1) collecting a 3D image of the system precision verification device, collecting a positive lateral perspective 2D image of the system precision verification device, and registering the obtained 3D image and the 2D image;
(2) selecting a simulation channel from the 3D image as a planning channel, taking the simulation channel as a target pose of a connecting line of two detection points of a verification piece arranged at the tail end of the mechanical arm, and calculating a motion track of the mechanical arm according to the target pose;
(3) transferring the system precision verification device to the pose of a measurement planning channel under a measurement environment as a reference value;
(4) calculating to obtain the motion trail of the mechanical arm under the measuring environment by combining the motion trail of the mechanical arm obtained in the step (2), and controlling the motion of the mechanical arm according to the motion trail;
(5) and measuring the pose of the mechanical arm after the mechanical arm moves to the position as an actual value, and calculating the error between the reference value and the actual value according to the actual value.
In the step (1), the positive lateral perspective 2D image of the system precision verification device is acquired after the posture change of the patient in the posture simulation operation of the movable vertebral segment in the system precision verification device is adjusted.
The motion trail of the mechanical arm in the measurement environment obtained by calculation in the step (4) is specifically as follows:
(41) calculating to obtain a transformation relation between a 3D image coordinate system and an optical tracker coordinate system in a measuring environment;
(42) acquiring the pose of the tracer at the tail end of the mechanical arm through an optical tracker and calculating to obtain the current pose of the verification piece;
(43) and (3) calculating to obtain the motion trail of the mechanical arm under the measuring environment by combining the step (2).
The reference value is the channel point coordinate of the selected channel
And
wherein
iThe code is a channel code number,
i=1,2,3, 4; the actual value is the coordinates of two detection points of the certificate checking piece
And
;
the precision error is calculated according to a relative distance formula between the twoLij:
Wherein:
in the formula (I), the compound is shown in the specification,jthe code refers to the code number of the measuring point of the corresponding channel point, and 1 and 2 are taken;Lijindicating a specified channeliOf the passage pointjThe distance between the two connecting points of the verification piece.
Has the advantages that: the method can rapidly and accurately analyze the space positioning precision based on the 2D-3D image registration, provides a basis for theoretical data analysis for correction and improvement of the image registration precision, and ensures the precision of a navigation positioning system; the image acquisition and the execution measurement are carried out in two space environments, so that the influence of the radiation environment on the measurement equipment is effectively avoided; and the planning of a plurality of groups of channels and the reference measurement can be carried out in one step, thereby greatly improving the test efficiency.
Detailed Description
The invention is further elucidated with reference to the drawings and the embodiments.
Fig. 1(a) is a right side view of the precision verification tool, and as shown in fig. 1(a), the system precision verification device of the present invention includes the precision verification tool and a probe used in cooperation therewith;
as shown in fig. 1(a), the precision verification tool comprises abase 1,vertebral segments 2 and atool tracer 3, wherein the precision verification tool comprises twovertebral segments 2, namely a fixedvertebral segment 22 and a movablevertebral segment 21, and the fixed vertebral segment 20 is fixedly arranged on thebase 1; the movablevertebral segment 21 is arranged on the mounting seat at the bottom of the movable vertebral segment through a spherical hinge structure, and the mounting seat is fixedly connected on thebase 1, so that the posture angle of the movablevertebral segment 21 can be adjusted within a certain range on thebase 1. A plurality ofchannel points 4 are fixedly embedded on the front side and the rear side of eachvertebral segment 2 respectively, and thechannel points 4 are steel balls with the diameter of 4 mm. The arrangement of the channel points of thevertebral segment 2 takes the front side of the vertebral segment as an example, one channel point is fixed at the center of the vertebral body of thevertebral segment 2, one channel point can be fixed at each of the two transverse processes of the joint of thevertebral segment 2, or one channel point is fixed at only one transverse process of the joint; the channel point at the transverse process of the joint and the channel point at the center of the vertebral body form a channel path, and the distance between the two is 6-10 mm. The design is to simulate the channel path of the vertebral body operation, and the channel path is as close to the operation scene as possible, namely a channel can be established through a connecting line between a channel point at the central position and a channel point at the transverse process position of the joint and is used as the reference of the execution pose of the mechanical arm. Accordingly, the posterior side of the vertebral segment may be designed as such, but the present invention is not limited thereto, and in the present invention, as long as at least one access point is provided at the vertebral body of the vertebral segment and at least one access point is provided at the transverse process of the joint of the vertebral segment, several access paths from the transverse process of the joint to the vertebral body can be formed.
A plurality ofregistration points 5 are embedded on the upper surface of thebase 1. Theregistration points 5 are steel balls with the diameter of 4mm, the number of the steel balls is 3-5, and the registration points are the characteristic of establishing the relation between an image coordinate system and a tool tracer coordinate system. All theregistration points 5 are on the same horizontal plane, and the distance between theregistration points 5 is not less than 10 mm. Thetooling tracer 3 is a standard tracer used in cooperation with an Optical Tracking System (OTS), and is fixedly mounted on the front end face of the precision verification tooling, as shown in fig. 1 (b).
The probe comprises abody 6, a mounting plate 7 and a detection point 8, as shown in fig. 2. Themain body 6 is a gradually-changed cylinder, the middle radius of the main body is large, and the main body is used for being matched with an assembling hole of the mechanical arm end effector; the radius of the two ends is small, and the detection points 8 are fixedly arranged. The mounting plate 7 is a disc with a protrusion and is fixed at a position of one end of the large-radius part of themain body 6, and the disc is in contact with the end face of a mounting hole of the mechanical arm end effector during assembly to play a role in axial limiting; the bulges on the disc are designed into short cylinders, are similar to pins, are matched with pin holes formed in the end face of the assembling hole of the mechanical arm end effector and play a role in circumferential limiting. The detection points 8 are steel balls with the diameter of 6mm, the number of the detection points is 2, the detection points are respectively and fixedly arranged on two sides of themain body 6, and a connecting line of the two detection points 8 is coaxial with themain body 6.
The invention also provides a system precision verification method based on 2D-3D image registration, as shown in FIG. 3, comprising the following steps:
(1) performing three-dimensional scanning on the precision verification tool shown in fig. 1 by using a C-arm machine to obtain 3D image data of a vertebra, a registration point and a channel point in the precision verification tool;
(2) fine-adjusting the pose of a movablevertebral segment 21 in the precision verification tool, wherein the adjustment range is 5-15 degrees deviated from the original pose, simulating that the intraoperative position changes, and performing positive lateral perspective imaging on the precision verification tool by using a C-arm machine to obtain positive lateral perspective image data of the vertebral segment, the registration point and the channel point in the precision verification tool;
wherein, the posture adjustment of the movablevertebral segment 21 is: the lower end of the movablevertebral segment 21 is connected with the mounting seat through a spherical hinge, so that the vertebral segment can rotate at 3 rotational degrees of freedom relative to the mounting seat, the vertebral segment is manually rotated to deviate from an original posture by 5-15 degrees, and posture angle change caused by natural movement of the vertebral segment in a simulation operation and before the operation is simulated;
(3) registering the 2D image and the 3D image;
(4) planning a channel in the 3D image, and then transmitting the planned channel to a navigation module through a series of transformations; planning a channel refers to selecting one group of channel points of a certain vertebra segment in a 3D image as an object, and connecting two points of the group of channel points to obtain a channel point connecting line;
the logic of the transformation passing is as follows:
obtaining the spatial position of the tooling tracer through the OTS, obtaining the position relation between the tooling tracer and the registration point on the precision verification tooling through the model parameters, further obtaining the spatial position of the registration point, and obtaining the transformation relation T between the 2D image coordinate system and the OTS coordinate system according to the image position of the registration point in the 2D image1(ii) a Obtaining a transformation relation T between a 3D image coordinate system and a 2D image coordinate system according to the registration of the 2D image and the 3D image in the step (3)2(ii) a Finally obtaining the transformation relation T between the 3D image coordinate system and the OTS coordinate system, wherein T = T1•T2;
(5) Performing path navigation planning on a probe at the tail end of the mechanical arm to a planning channel through a navigation module;
selecting a group of planned channel points in the 3D image as a target, and enabling one point of the group of channel points to be used as a target point of a lower detection point of a probe at the tail end of the mechanical arm, namely determining the position of the target; enabling the channel point connecting line to serve as a target pose of a connecting line of two detection points of the probe at the tail end of the mechanical arm, and obtaining the target pose of the probe in the OTS coordinate system according to the transformation relation between the 3D image coordinate system and the OTS coordinate system obtained in the step (4); identifying the tracer at the tail end of the mechanical arm through the OTS, and calculating according to the installation parameters of the probe to obtain the current pose of the probe, as shown in FIG. 4; according to the current pose and the target pose of the probe in the OTS coordinate system, the Cartesian space trajectory planning is carried out on the mechanical arm to obtain a motion trajectoryS;
(6) Withdrawing the precision verification tool from the X-ray machine room, transferring the precision verification tool to a measurement environment, arranging mechanical arm equipment, and also transferring and arranging an OTS at a proper position, so that a tracer on the mechanical arm end effector and a tracer of the precision verification tool are both visible in the OTS;
(7) due to the rearrangement of the equipment, the pose change of the tooling tracer of the precision verification tooling relative to the OTS system is recorded as T1*And (5) calculating to obtain a new transformation relation T' = T between the 3D image coordinate system and the OTS coordinate system according to the step (4)1*•T1•T2. In fact, since the other transformation matrices are constant matrices, only T1*Changes with installation location, and the OTS system can track the tracer in real time to update the T1*Therefore, synchronous real-time transmission of 3D image data can be realized; at the moment, the tracer of the mechanical arm end effector is visible under the OTS, namely, a transformation matrix T of the end effector coordinate system relative to the OTS coordinate system is calibrated through the OTS system3;
(8) Measuring the position of the channel point of the selected channel after rearrangement by using contact type measuring equipment as a reference value; the method specifically comprises the following steps: using a three-coordinate measuring instrument to calibrate and measure each group of channel points of the vertebral segment to obtain the position of each group of channel points
And
,
ithe code is a channel code number,
i=1,2,3,4 in mm; further obtaining the position of the channel point of the selected channel;
(9) controlling the mechanical arm to reach a target point;
locking 3D image data in a navigation module, recording OTS poses of all channels, withdrawing the precision verification tool, inserting a probe into a mechanical arm end actuator, acquiring a mechanical arm end tracer through OTS, calculating to obtain the current pose of the probe, and planning a track according to the track calculated in the step (5)
SAnd (4) calculating the transformation relation between the new 3D image coordinate system and the OTS coordinate system obtained in the step (7) to obtain a new track plan
S' and controlling the mechanical arm to reach the position of the specified channel under the OTS tracking according to the control, and measuring the positions of detection points at two ends of the probe installed on the mechanical arm by using contact type measuring equipment as an actual value after the mechanical arm reaches the stable position;the method specifically comprises the following steps: calibrating the positions of detection points at two ends of a probe on an end effector of a mechanical arm by using a three-coordinate measuring instrument
And
;
(10) calculating and analyzing the difference error between the arrival axis and the channel axis according to the reference value and the actual value; the method specifically comprises the following steps: calculating the appointed channel according to the formula of relative distanceiOf the passage pointjDistance relative to probe axisLijAs an estimation of the image registration error, the unit is mm, and the calculation formula is as follows:
wherein:tis the intermediate variable(s) of the variable,
in the formula (I), the compound is shown in the specification,jthe code refers to the code number of the measuring point of the corresponding channel point, and 1 and 2 are taken.
The method can rapidly and accurately analyze the space positioning precision based on the 2D-3D image registration, and provides a basis for theoretical data analysis for correction and improvement of the image registration precision; the image acquisition and the execution measurement are carried out in two space environments, so that the influence of the radiation environment on the measurement equipment is effectively avoided; and the planning of a plurality of groups of channels and the reference measurement can be carried out in one step, thereby greatly improving the test efficiency.
Although the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the details of the foregoing embodiments, and various equivalent changes (such as number, shape, position, etc.) may be made to the technical solution of the present invention within the technical spirit of the present invention, and these equivalent changes are all within the protection scope of the present invention.