阅读说明：本技术 一种封闭体模内肿瘤位姿估计的方法 (Method for estimating pose of tumor in closed body mould ) 是由 郁树梅 后鹏程 孙荣川 匡绍龙 孙立宁 于 2019-10-29 设计创作，主要内容包括：本发明公开了一种封闭体模内肿瘤位姿估计的方法,包括以下步骤：在模拟肺内壁固定设置视觉纹理图；在模拟肺的壁面上安装单目内窥镜模拟肺部肿瘤,所述单目内窥镜朝向所述视觉纹理图设置；在模拟肺运动时,所述单目内窥镜采集视觉纹理图的视频帧；使用ORB-SLAM2算法对视频帧进行处理,重新建立关键帧判别准则,获得关键帧并对单目内窥镜的位姿进行求解；根据单目内窥镜的位姿获得模拟肿瘤位姿数据。其实现了对封闭体模内部肿瘤位姿的估计,结构简单,操作便捷,定位准确。(The invention discloses a method for estimating pose of tumor in a closed body mould, which comprises the following steps: fixedly arranging a visual texture map on the inner wall of the simulated lung; installing a monocular endoscope on the wall surface of the simulated lung to simulate lung tumor, wherein the monocular endoscope is arranged towards the visual texture map; when the lung motion is simulated, the monocular endoscope collects video frames of the visual texture map; processing the video frame by using an ORB-SLAM2 algorithm, reestablishing a key frame judgment criterion, obtaining a key frame and solving the pose of the monocular endoscope; and acquiring simulated tumor pose data according to the pose of the monocular endoscope. The method realizes estimation of the pose of the tumor in the closed body model, and has the advantages of simple structure, convenience in operation and accuracy in positioning.)

1. A method of closed body intramode tumor pose estimation comprising the steps of:

fixedly arranging a visual texture map on the inner wall of the simulated lung;

installing a monocular endoscope on the wall surface of the simulated lung to simulate lung tumor, wherein the monocular endoscope is arranged towards the visual texture map;

when the lung motion is simulated, the monocular endoscope collects video frames of the visual texture map;

processing the video frame by using an ORB-SLAM2 algorithm, reestablishing a key frame judgment criterion, obtaining a key frame and solving the pose of the monocular endoscope;

and acquiring simulated tumor pose data according to the pose of the monocular endoscope.

2. The method for closed body intramode tumor pose estimation according to claim 1, wherein said "re-establishing key frame criteria" specifically comprises: A. the requirement that the number of the inner points must exceed a set minimum threshold is met; B. satisfying one of three criteria, including:

a first criterion: MAX frames have passed since the last key frame insertion, MAX being the maximum value preset by ORB-SLAM 2;

the second criterion is that: at least past MIN frame from last inserting key frame, and local mapping process is in idle state, MIN is preset minimum value of ORB-SLAM 2;

the third criterion is that: the number of key frames in the key frame queue in the local mapping thread is not more than 3.

3. The method for closed body intramode tumor pose estimation of claim 1, wherein processing the video frames using the ORB-SLAM2 algorithm, re-establishing the keyframe decision criteria, obtaining keyframes and solving for the pose of the monocular endoscope comprises:

s41, inputting a video frame;

s42, extracting ORB characteristics from the original image and calculating a descriptor;

s43, estimating the motion of the monocular endoscope according to the matched feature points;

s44, reestablishing the key frame judgment criterion to enable the number of the interior points to exceed the set minimum threshold;

and S45, judging whether the current frame is a key frame, and solving the pose of the monocular endoscope according to the key frame.

4. The method of closed intramode tumor pose estimation according to claim 1, wherein the view angle of said monocular endoscope overlays a visual texture map.

5. The method of closing intramode tumor pose estimation of claim 1, wherein the key frame insertion condition of the ORB-SLAM2 algorithm is uniform insertion.

6. The method of closing in-mold tumor pose estimation of claim 1, wherein said obtaining simulated tumor pose data is three dimensional data.

7. The method of closing intramodal tumor pose estimation according to claim 1, wherein the simulated lung is disposed within a biomimetic simulated breathing model.

8. The method of closed intramodal tumor pose estimation according to claim 1, wherein the simulated lung is a lung shaped cavity balloon.

Technical Field

The invention relates to the technical field of a respiration tracking system of a radiotherapy robot, in particular to a method for estimating the pose of an in-mold tumor of an enclosed body.

Background

Tumors in the human thorax and abdomen, especially lung tumors, are usually accompanied by respiratory motion. The accurate positioning of the tumor in motion is an important content of the research of the radiotherapy robot at present. Because the tumor is located in the human body, for the motion acquisition of the internal tumor, a gold marker is implanted in the tumor or around the tumor in most clinical practice, and the position coordinates of the target area of the tumor are acquired by using an X-ray imaging device. Since long-term exposure to X-rays can cause damage to normal tissues surrounding the tumor, direct real-time localization of the tumor using imaging techniques such as X-ray is not desirable.

Therefore, tracking the respiratory motion of the tumor by using the body surface information becomes one of the key technologies for realizing precise radiotherapy by using a three-dimensional radiotherapy robot, and the most mainstream method at present is to predict the arrival position of the tumor in advance and plan the motion of a mechanical arm by using a body surface mark point and an associated model of the tumor in the body, so that the beam of a linear accelerator can track the motion of the tumor in real time, and the aim of precise radiotherapy is fulfilled.

In order to establish a correlation model between the body surface motion information and the motion of the tumor in the body, on one hand, a characterization method of the body surface motion information needs to be researched. The characterization method for researching the complete body surface motion information mainly has two directions. First, a study was developed around the number of finite body surface markers. And secondly, a body surface motion information characterization method based on a multi-modal sensor. On the other hand, the movement of the tumor in the body needs to be acquired. In order to avoid direct acquisition of the real tumor motion of the human body, researchers mostly obtain the motion by simulating the tumor in a respiratory phantom. The acquisition mode of the tumor movement in the phantom is mainly to implant a mark into the simulated tumor and acquire the movement of the simulated tumor by means of an imaging technology such as X-ray, but the cost is high and the operation is complex.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for estimating the pose of a tumor in a closed body mould, which realizes the estimation of the pose of the tumor in the closed body mould, and has the advantages of simple structure, convenient operation and accurate positioning.

In order to solve the technical problem, the invention provides a method for estimating the pose of an intramode tumor of a closed body, which comprises the following steps:

fixedly arranging a visual texture map on the inner wall of the simulated lung;

installing a monocular endoscope on the wall surface of the simulated lung to simulate lung tumor, wherein the monocular endoscope is arranged towards the visual texture map;

when the lung motion is simulated, the monocular endoscope collects video frames of the visual texture map;

processing the video frame by using an ORB-SLAM2 algorithm, reestablishing a key frame judgment criterion, obtaining a key frame and solving the pose of the monocular endoscope;

and acquiring simulated tumor pose data according to the pose of the monocular endoscope.

Preferably, the "reestablishing the key frame criterion" specifically includes: A. the requirement that the number of the inner points must exceed a set minimum threshold is met; B. satisfying one of three criteria, including:

a first criterion: MAX frames have passed since the last key frame insertion, MAX being the maximum value preset by ORB-SLAM 2;

the second criterion is that: at least past MIN frame from last inserting key frame, and local mapping process is in idle state, MIN is preset minimum value of ORB-SLAM 2;

the third criterion is that: the number of key frames in the key frame queue in the local mapping thread is not more than 3.

Preferably, the "processing the video frame by using the ORB-SLAM2 algorithm, reestablishing the key frame criterion, obtaining the key frame, and solving the pose of the monocular endoscope" specifically includes:

s41, inputting a video frame;

s42, extracting ORB characteristics from the original image and calculating a descriptor;

s43, estimating the motion of the monocular endoscope according to the matched feature points;

s44, reestablishing the key frame judgment criterion to enable the number of the interior points to exceed the set minimum threshold;

and S45, judging whether the current frame is a key frame, and solving the pose of the monocular endoscope according to the key frame.

Preferably, the viewing angle of the monocular endoscope overlays the visual texture map.

Preferably, the key frame insertion condition of the ORB-SLAM2 algorithm is uniform insertion.

Preferably, the "obtaining simulated tumor pose data" is three-dimensional data.

Preferably, the simulated lung is arranged in a bionic simulated breathing model.

Preferably, the simulated lung is a lung-shaped cavity balloon.

The invention has the beneficial effects that:

1. the invention realizes the pose estimation of the tumor motion by installing the monocular endoscope and the visual texture map in the simulated lung of the bionic human body breathing model, simulating the tumor motion by using the motion of the endoscope through a visual positioning method and realizing the pose estimation of the endoscope motion by using an ORB-SLAM2 algorithm.

2. The invention realizes the estimation of the pose of the tumor in the closed body model without any auxiliary imaging equipment.

3. The invention has simple structure, convenient operation and accurate positioning.

Drawings

FIG. 1 is a flow chart of the present invention FIG. 1 is a method of the present invention;

FIG. 2 is a schematic view of a monocular endoscope mounted on a simulated lung;

FIG. 3 is a visual texture map;

FIG. 4 is a key frame obtained using the ORB-SLAM2 algorithm;

FIG. 5 is a graph of a simulated tumor motion trajectory;

fig. 6 is a graph of simulated tumor motion in three components.

Detailed Description

The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.

Referring to fig. 1, the invention discloses a method for estimating the pose of an intramode tumor of an enclosed body, which comprises the following steps:

firstly, fixedly arranging a visual texture map on the inner wall of the simulated lung. Since the simulated lung is deformed during the simulated breathing movement, the visual texture map needs to be fixed in order to avoid the movement of the visual texture map. The specific operation is that an opening is cut on the simulated lung, and the hard plate of the texture map is pasted inside the lung. And the same size of hard plate is adhered to the corresponding position outside the lung for reinforcement. Fig. 3 is a visual texture map.

And secondly, installing a monocular endoscope on the wall surface of the simulated lung to simulate lung tumor, wherein the monocular endoscope is arranged towards the visual texture map. And adjusting the visual angle of the endoscope to cover the visual texture map, and ensuring that the visual angle does not remove the range of the texture map in the moving process of the endoscope. The simulated lung is arranged in the bionic simulated breathing model. The simulated lung is a lung-shaped cavity air sac. Fig. 2 is a schematic view of a monocular endoscope mounted on a simulated lung.

Of course, the monocular endoscope can be installed on the simulated lung to simulate the lung tumor, and then the visual texture map can be fixedly arranged on the inner wall of the simulated lung.

And step three, when the lung motion is simulated, the monocular endoscope collects the video frame of the visual texture map.

And step four, processing the video frame by using an ORB-SLAM2 algorithm, reestablishing a key frame judgment criterion, obtaining a key frame and solving the pose of the monocular endoscope.

Is a key frame obtained using the ORB-SLAM2 algorithm. The ORB-SLAM2 algorithm, to avoid information redundancy and reduce the amount of computation, the insertion of key frames must satisfy the following conditions: 1. the number of inner points must exceed a set minimum threshold, and the degree of overlap cannot be too large; the three satisfy one of the following conditions: 2.1, the MAX frame has passed since the last key frame insertion, MAX being the preset maximum value of ORB-SLAM 2; 2.2, at least past MIN frames are inserted into the key frame at the last time, the local mapping process is in an idle state, and MIN is a preset minimum value of ORB-SLAM 2; 2.3, the number of key frames in the key frame queue in the local mapping thread is not more than 3. Due to its application in the intra-pulmonary environment, the endoscope moves only within a limited range, resulting in too high an image overlap. Using default keyframe insertion conditions can result in fewer keyframes that do not present a real-time pose estimate for the camera. Therefore, by modifying the relaxed key frame insertion condition and removing the judgment of the key frame insertion condition, key frames can be inserted with uniform frequency.

The method for processing the video frame by using the ORB-SLAM2 algorithm, reestablishing the key frame judgment criterion, obtaining the key frame and solving the pose of the monocular endoscope specifically comprises the following steps:

s41, inputting a video frame;

s42, extracting ORB characteristics from the original image and calculating a descriptor;

s43, estimating the motion of the monocular endoscope according to the matched feature points;

s44, reestablishing a key frame judgment criterion;

and S45, judging whether the current frame is a key frame, and solving the pose of the monocular endoscope according to the key frame.

The key frame insertion condition of the ORB-SLAM2 algorithm is uniform insertion. Fig. 4 shows key frames obtained by using the ORB-SLAM2 algorithm, and small points are feature points used for matching between image frames.

And fifthly, acquiring simulated tumor pose data according to the pose of the monocular endoscope. The pose of the monocular endoscope is the pose of the simulated tumor. And simulating the tumor pose data into three-dimensional data.

As shown in fig. 5, the movement trace of the endoscope (tumor) obtained by using the ORB-SLAM2 is shown. As can be seen from the figure, the trajectory of the tumor pose conforms to the law of motion, and the drift is small.

As shown in fig. 6, the motion of the endoscope (tumor) with respect to time is shown in three motion components X, Y, and Z. It can be seen that the amplitude of the primary component (Z) motion is large; on the sub-component 1(X), the motion amplitude is small; on the sub-component 2(Y), the motion is substantially stationary. The obtained tumor motion accords with the real lung tumor motion rule of the human body, and the result shows that the method can realize the estimation of the pose of the tumor in the closed body mould.

It is worth noting that the bionic robot is applied to a bionic experiment platform, is not used in actual medical treatment, and does not act on a human body.

The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.