Surgical positioning error calculation methods, positioning error correction methods and equipment

Abstract

The present invention provides a method for calculating surgical positioning errors, a method for correcting positioning errors and a device. The method is applied to the field of medical images. The method comprises: obtaining a patient's preoperative two-dimensional medical perspective image and two-dimensional pixel coordinates and image parameters of a target point therein, wherein the image parameters include basic attributes of the medical perspective image and geometric parameters of an imaging system; calculating the three-dimensional world coordinates of the target point according to the two-dimensional pixel coordinates and the image parameters; obtaining the three-dimensional world coordinates of a light source point by calculating the target coordinate conversion matrix; calculating the three-dimensional world coordinates of the rotation center of the imaging system according to the three-dimensional world coordinates of the light source point and the three-dimensional world coordinates of the target point; and calculating the error vector between the three-dimensional world coordinates of the rotation center and the three-dimensional world coordinates of the target point. The present invention realizes accurate error correction and improves the surgical treatment effect.

Description

Technical Field

[0001] The present invention relates to the field of medical images, and in particular to a surgical positioning error calculation method, a positioning error correction method and a device. Background Art

[0002] Perspective images, as black-and-white images formed using X-ray perspective technology, generate image data of varying brightness based on differences in the degree of X-ray absorption by human tissues. CBCT images and DSA images are typical applications. In the field of surgical robots, CBCT images can be further converted into perspective images and converted into high-resolution three-dimensional slice data through specific algorithms, thereby accurately locking onto the center of the target lesion or other target points. Once these target image coordinates are acquired, the optical navigation module guides the robotic arm to operate, which not only improves the success rate of the first needle insertion, but also shortens the operation time. The entire process is highly dependent on precise image guidance.

[0003] In the field of tumor radiotherapy, the core application of CBCT (cone beam computed tomography) is image-guided radiotherapy. When a patient receives treatment for the first time, he or she will be positioned according to the three-dimensional coordinates determined by the treatment plan. Subsequently, a CBCT scan will be performed before formal treatment. This step is intended to provide doctors with real-time images of the patient before radiotherapy. The patient's position can then be adjusted at any time based on the immediate impact. However, in the current technology, when the CBCT image is automatically fused and registered with the CT image in the planning stage, the patient's anatomical structure, the accuracy of the instrument, the imaging problem, and the operator's experience level will cause the registration to be time-consuming and complex, resulting in errors in the registration, which to a certain extent limits the precise correction of the positioning. Any slight error may cause a change in the dose, thereby adversely affecting the effect of radiotherapy. Therefore, improving the efficiency and accuracy of registration is crucial to ensuring the efficacy of radiotherapy. Summary of the invention

[0004] In view of this, the present invention provides a method for calculating surgical positioning error, comprising:

[0005] Acquire a preoperative two-dimensional medical perspective image of the patient and two-dimensional pixel coordinates and image parameters of a target point therein, wherein the image parameters include basic attributes of the medical perspective image and geometric parameters of an imaging system;

[0006] Calculate the three-dimensional world coordinates of the target point according to the two-dimensional pixel coordinates and the image parameters;

[0007] Using the target coordinate transformation matrix, the three-dimensional world coordinates of the light source point are calculated;

[0008] Calculate the three-dimensional world coordinates of the rotation center of the imaging system according to the three-dimensional world coordinates of the light source point and the three-dimensional world coordinates of the target point;

[0009] An error vector between the three-dimensional world coordinates of the rotation center and the three-dimensional world coordinates of the target point is calculated.

[0010] Optionally, calculating the three-dimensional world coordinates of the target point according to the two-dimensional pixel coordinates and the image parameters includes:

[0011] Calculate the three-dimensional world coordinates of the initial target point according to the two-dimensional pixel coordinates and the image parameters;

[0012] updating the image parameters of the medical fluoroscopic image according to the three-dimensional world coordinates of the initial target point;

[0013] Calculation is performed based on the two-dimensional pixel coordinates and the updated image parameters to obtain the three-dimensional world coordinates of the actual target point.

[0014] Optionally, the two-dimensional medical perspective image is a perspective image taken at any two different viewing angles, wherein an included angle between a first viewing angle and a second viewing angle is between 30° and 150°.

[0015] Optionally, the image parameters include image resolution of the medical fluoroscopic image, pixel spacing, the distance from the light source point to the patient in the imaging system, the distance from the light source point to the detection plate in the imaging system, the first angle, the second angle, the first angle increment, and the second angle increment.

[0016] Optionally, calculating the three-dimensional world coordinates of the initial target point according to the two-dimensional pixel coordinates and the image parameters includes:

[0017] Calculating an initial target coordinate conversion matrix according to the image parameters, the initial target coordinate conversion matrix is ​​used to convert the two-dimensional pixel coordinates of the target point into three-dimensional world coordinates, wherein the initial target coordinate conversion matrix is ​​composed of conversion parameters of a two-dimensional pixel coordinate system, a two-dimensional image coordinate system, a three-dimensional camera coordinate system, and a three-dimensional world coordinate system;

[0018] Substituting the two-dimensional pixel coordinates of the target point of the dual-view into the initial target coordinate conversion matrix, and calculating the to-be-processed three-dimensional world coordinates of the target point of the dual-view;

[0019] Processing and calculation are performed according to the target point of the dual perspectives and the three-dimensional world coordinates to be processed to obtain the three-dimensional world coordinates of the initial target point of the dual perspectives.

[0020] Optionally, updating the image parameters of the medical fluoroscopic image according to the three-dimensional world coordinates of the initial target point includes:

[0021] The distance from the light source point to the plane where the target point is located in the imaging system is calculated according to the three-dimensional world coordinates of the initial target point, and the distance from the light source point to the patient target plane in the imaging system is obtained;

[0022] The updated pixel pitch is obtained by performing calculation based on the distance from the light source point to the detection plate in the imaging system and the pixel pitch.

[0023] Optionally, calculating according to the two-dimensional pixel coordinates and the updated image parameters to obtain the three-dimensional world coordinates of the actual target point includes:

[0024] Calculate a target coordinate conversion matrix according to the updated image parameters, wherein the target coordinate conversion matrix is ​​used to convert the two-dimensional pixel coordinates of the target point into three-dimensional world coordinates, wherein the target coordinate conversion matrix is ​​composed of conversion parameters of a two-dimensional pixel coordinate system, a two-dimensional image coordinate system, a three-dimensional camera coordinate system, and a three-dimensional world coordinate system;

[0025] The two-dimensional pixel coordinates of the target point of the dual-viewing angle are brought into the target coordinate transformation matrix to calculate the three-dimensional world coordinates of the target point after updating the dual-viewing angle;

[0026] Processing and calculation are performed based on the updated target points and three-dimensional world coordinates of the dual perspectives to obtain the three-dimensional world coordinates of the actual target points of the dual perspectives.

[0027] Optionally, calculating the three-dimensional world coordinates of the rotation center of the imaging system according to the three-dimensional world coordinates of the light source point and the three-dimensional world coordinates of the target point includes:

[0028] Draw a first projection path line according to the three-dimensional world coordinates of the light source point of the first viewing angle and the three-dimensional world coordinates of the actual target point;

[0029] Draw a second projection path line according to the three-dimensional world coordinates of the light source point of the second viewing angle and the three-dimensional world coordinates of the actual target point;

[0030] A common point on the first projection path line and the second projection path line is selected as a rotation center, and the three-dimensional world coordinates of the rotation center are calculated.

[0031] A second aspect of the present invention provides a surgical positioning error calculation device, which includes: a processor and a memory connected to the processor; wherein the memory stores instructions executable by the processor, and the instructions are executed by the processor so that the processor executes the above-mentioned surgical positioning error calculation method.

[0032] A third aspect of the present invention provides a method for correcting a positioning error, comprising: for a treatment bed and a patient positioned according to three-dimensional coordinates in a surgical plan, taking a preoperative two-dimensional medical perspective image, and obtaining an error vector using a surgical positioning error calculation method;

[0033] The light source system and / or the treatment couch in the imaging system is moved according to the error vector so that the target point is located at the center of the projected image.

[0034] The surgical positioning error calculation method provided by the present invention obtains the patient's preoperative two-dimensional medical perspective image and related coordinates and parameters, and then accurately calculates the three-dimensional world coordinates of the target point and the light source point according to the target transformation matrix, and determines the three-dimensional position of the rotation center of the imaging system according to the three-dimensional world targets of the light source point and the target point. In this process, it is particularly important to calculate the three-dimensional world coordinate error vector between the rotation center and the target point, because the purpose is to place the target point at the center of the two-dimensional medical perspective image, that is, the area expected to be observed can be in the center of the two-dimensional medical perspective image, so that the light source can vertically illuminate the target. When the projection of the target is located at the center of the two-dimensional medical perspective image, the projection light will be vertically illuminated along the optical axis onto the imaging plane, thereby reducing image distortion caused by factors such as lens distortion, which helps to ensure that the irradiation field in the radiotherapy plan is consistent with the actual irradiation situation. Thereby improving the accuracy of the operation and effectively reducing the treatment risk caused by positioning errors.

[0035] The positioning error correction method provided by the present invention adjusts the light source system and / or the patient's treatment bed according to the error vector, which has advantages in accuracy, safety and repeatability compared to temporarily changing the surgical plan. Therefore, in radiotherapy practice, when it is found that there is a large error between the actual position of the patient and the position in the medical plan, it is usually preferred to determine and correct the error through image registration rather than directly changing the surgical plan. This can ensure the accuracy of the radiotherapy process, that is, ensure that the treatment rays are accurately focused on the target area while minimizing damage to surrounding healthy tissues. In addition, determining and correcting errors through image registration can also improve the safety of treatment and avoid the uncertainty and risks that may be caused by directly modifying the surgical plan. Finally, this method also has good repeatability, which can ensure that in future radiotherapy processes, the patient can maintain a position consistent with the planned image, thereby further improving the stability and effect of the treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 is a flow chart of a method for calculating surgical positioning error in an embodiment of the present invention;

[0038] Figure 2It is a projection schematic diagram in an embodiment of the present invention;

[0039] Figure 3 is a schematic diagram of calculating a target point in an embodiment of the present invention;

[0040] Figure 4 is a schematic diagram of a mobile light source system in an embodiment of the present invention;

[0041] Figure 5 Schematic diagram of a treatment bed for moving patients in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0044] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0046] like Figure 1 As shown, an embodiment of the present invention provides a method for calculating surgical positioning errors, which is executed by an electronic device such as a computer or a server, and specifically includes:

[0047] S1, obtaining the patient's preoperative two-dimensional medical fluoroscopic image and the two-dimensional pixel coordinates and image parameters of the target points therein, wherein the image parameters include basic properties of the medical fluoroscopic image and geometric parameters of the imaging system.

[0048] The imaging system is a C-arm X-ray machine, including a light source system, which includes a transmitter and a receiver. The transmitter and the receiver are respectively located on both sides of the medical bed. X-rays are mainly emitted through the transmitter. After these rays penetrate the human body, they are attenuated, and then the receiver receives these attenuated signals to obtain perspective images. Among them, X-rays are not "light" in the traditional sense. The present invention can be broadly understood as a system that generates radiation sources required for imaging. Then the transmitter (i.e., X-ray source) can be regarded as part of the light source system, and the light source point mentioned below refers to the transmitter. At the same time, the C-arm can rotate around the patient to obtain more comprehensive perspective images from different angles. The C-arm X-ray machine is used to rotate at a predetermined angle to obtain a number of perspective images, and perspective images of any multiple viewing angles (the number is much less than the total number of perspective images) are selected.

[0049] Perspective images are two-dimensional pixel images, black-and-white images obtained through X-ray perspective technology, which use the different absorption of X-rays by different tissues of the human body to form data of different brightness. Common ones include CBCT images and DSA images. The target point can be the center of a tumor lesion, a body surface positioning marker, or the tip of a puncture needle or ablation needle in the body. The acquisition method is not limited to manual selection or extraction by traditional methods or machine learning methods. The two-dimensional pixel coordinates (u, v) of the target point with the pixel image as the coordinate system are obtained. The two-dimensional pixel coordinates are obtained before the patient's surgery, such as radiotherapy. Image parameters are built-in default values, which can be read from the standard format image of the DICOM image, or can be obtained by technicians or doctors based on actual environment.

[0050] S2, calculate the three-dimensional world coordinates of the target point based on the two-dimensional pixel coordinates and image parameters.

[0051] S3, using the target coordinate transformation matrix, calculate the three-dimensional world coordinates of the light source point.

[0052] S4, calculating the three-dimensional world coordinates of the rotation center of the imaging system according to the three-dimensional world coordinates of the light source point and the three-dimensional world coordinates of the target point.

[0053] The rotation center is the fixed point around which the transmitting and receiving ends of the C-arm rotate. The rotation center can be vertically projected to the center of the 2D perspective image.

[0054] S5, calculating an error vector between the three-dimensional world coordinates of the rotation center and the three-dimensional world coordinates of the target point.

[0055] This embodiment obtains the patient's preoperative two-dimensional medical perspective image and related coordinates and parameters, and then accurately calculates the three-dimensional world coordinates of the target point according to the target transformation matrix, and determines the three-dimensional position of the rotation center of the imaging system according to the three-dimensional world targets of the light source point and the target point. In this process, it is particularly important to calculate the three-dimensional world coordinate error vector between the rotation center and the target point, because the purpose is to place the target point at the center of the two-dimensional medical perspective image, that is, the area expected to be observed can be in the center of the two-dimensional medical perspective image, so that the light source can vertically illuminate the target. When the projection of the target is located at the center of the two-dimensional medical perspective image, the projection light will be vertically illuminated along the optical axis onto the imaging plane, thereby reducing image distortion caused by factors such as lens distortion, which helps to ensure that the irradiation field in the radiotherapy plan is consistent with the actual irradiation situation. This improves the accuracy of the operation and effectively reduces the treatment risk caused by positioning errors.

[0056] In one embodiment, calculating the three-dimensional world coordinates of the target point according to the two-dimensional pixel coordinates and the image parameters in step S2 includes:

[0057] S21, calculating the three-dimensional world coordinates of the initial target point according to the two-dimensional pixel coordinates and image parameters;

[0058] S22, updating the image parameters of the medical fluoroscopic image according to the three-dimensional world coordinates of the initial target point;

[0059] S23, calculate according to the two-dimensional pixel coordinates and the updated image parameters to obtain the three-dimensional world coordinates of the actual target point. The three-dimensional world coordinates of the actual target point can be used to know the center position of the tumor lesion in the patient's body, or the position of the body surface positioning marker or the needle tip of the puncture needle or ablation needle in the body.

[0060] This embodiment preliminarily determines the three-dimensional world coordinates of the target point and uses this coordinates to optimize the image parameters. In the process of converting the two-dimensional pixel coordinates into three-dimensional world coordinates using the updated image parameters, a reprocessing step of error correction is further implemented to ensure the high accuracy of the three-dimensional world coordinates of the actual target point finally obtained.

[0061] Preferably, the preoperative two-dimensional medical fluoroscopic image of the patient acquired in step S1 is a fluoroscopic image taken at any two different viewing angles, wherein the angle between the first viewing angle and the second viewing angle is between 30° and 150°.

[0062] For example, a C-arm X-ray machine rotates 180° in half a circle to obtain 180 frames of perspective images, and two frames of perspective images from two perspectives are selected. Selecting perspective images from multiple perspectives can avoid the loss of single-perspective information and reduce the time for acquiring images and algorithm calculations. Perspective images from too many perspectives will increase the calculation cost. Therefore, two or more perspectives can provide complementary information, reduce the amount of processing, and quickly obtain accurate information.

[0063] The angle between the perspective images of the two perspectives is controlled within the preset angle range, which can ensure that there is a certain parallax (depth and distance of the object) between the two perspective images, which is helpful for subsequent 3D reconstruction or target point positioning. If the angle is too small, it may lead to insufficient parallax, thus affecting the accuracy of 3D reconstruction. On the contrary, if the angle is too large, although the parallax will increase, it may also lead to a reduction in the overlap between the images, increasing the difficulty of subsequent processing.

[0064] The image parameters acquired in step S1 include basic attributes of medical fluoroscopic images and geometric parameters of the imaging system, wherein the image parameters include image resolution row, cols, pixel spacing, distance SOD from the light source point to the patient in the imaging system, distance SID from the light source point to the detection board in the imaging system, first angle , Second Angle , first angle increment , Second angle increment .

[0065] Among them, the distance from the light source point to the detection plate in the imaging system is the distance from the transmitting end to the receiving end of the C-arm X-ray machine; the first angle and the second angle are the initial angles of the two selected frames of perspective images, and the first angle increment and the second angle increment correspond to the angle of the frame image rotation. For example, the angle of the 90th frame is the corresponding initial angle plus the angle increment, that is, the angle of the corresponding viewing angle. The following description takes the dual viewing angles of 0° and 90° as an example. In one embodiment, the target coordinate conversion matrix is ​​calculated according to the image parameters, and the target coordinate conversion matrix is ​​obtained by the conversion matrix between the two-dimensional pixel coordinate system and the two-dimensional image coordinate system, the conversion matrix between the two-dimensional image coordinate system and the three-dimensional camera coordinate system, and the conversion matrix between the three-dimensional camera coordinate system and the three-dimensional world coordinate system. Among them, the conversion matrix between the two-dimensional pixel coordinate system and the two-dimensional image coordinate system is calculated by the image resolution and the pixel spacing, the conversion matrix between the two-dimensional image coordinate system and the three-dimensional camera coordinate system is obtained by the distance from the light source point to the patient, and the conversion matrix between the three-dimensional camera coordinate system and the three-dimensional world coordinate system is calculated by the first angle, the second angle, the first angle increment, and the second angle increment.

[0066] Furthermore, in step S21, the three-dimensional world coordinates of the initial target point are calculated according to the two-dimensional pixel coordinates and the image parameters, including:

[0067] S211, calculating an initial target coordinate transformation matrix according to the image parameters, the initial target coordinate transformation matrix is ​​used to transform the two-dimensional pixel coordinates of the target point into three-dimensional world coordinates, wherein the initial target coordinate transformation matrix is ​​composed of transformation parameters of a two-dimensional pixel coordinate system, a two-dimensional image coordinate system, a three-dimensional camera coordinate system and a three-dimensional world coordinate system.

[0068] The transformation matrix among the 2D pixel coordinate system, 2D image coordinate system, 3D camera coordinate system and 3D world coordinate system is calculated according to the image parameters to transform the 2D pixel coordinates of the target point into 3D world coordinates. All coordinate systems satisfy the right-hand coordinate system.

[0069] S212, bringing the two-dimensional pixel coordinates of the target point of the dual perspective into the initial target coordinate conversion matrix, and calculating the to-be-processed three-dimensional world coordinates of the target point of the dual perspective.

[0070] S213, performing processing and calculation according to the target point of the dual perspectives and the three-dimensional world coordinates to be processed, to obtain the three-dimensional world coordinates of the initial target point of the dual perspectives.

[0071] Specifically, an initial target coordinate transformation matrix is ​​first calculated according to the image parameters, and then the two-dimensional pixel coordinates of the target point of the dual perspective are converted into three-dimensional world coordinates using the initial target coordinate transformation matrix, and finally post-processing is performed to obtain the three-dimensional world coordinates of the target point.

[0072] The three-dimensional world coordinates obtained by accurate calculation in this embodiment provide more accurate initial conditions for the calculation of the target coordinate conversion matrix in the subsequent steps. The image parameters updated in step S22 will provide more accurate initial conditions for the subsequent steps and also help to optimize the coordinate conversion matrix. Therefore, the processing and calculation in steps S3-S5 will be able to be performed on a more accurate and reliable basis, thereby ensuring the accuracy of the final result.

[0073] Among them, step S213 processes and calculates the target point of the dual perspectives and the three-dimensional world coordinates to be processed to obtain the three-dimensional world coordinates of the initial target point of the dual perspectives, including:

[0074] S2131, using the initial target coordinate transformation matrix, calculate the three-dimensional world coordinates of the light source point of the dual perspective.

[0075] S2132, connecting the light source point of the first viewing angle with the corresponding target point to obtain a first connecting line, and connecting the light source point of the second viewing angle with the corresponding target point to obtain a second connecting line.

[0076] S2133, select a point on the first line and the second line respectively, so that the midpoint of the line connecting the two selected points is closest to the first line and the second line.

[0077] S2134, taking the midpoint as the initial target point, and obtaining the three-dimensional world coordinates of the initial target point.

[0078] The specific projection diagram is as follows Figure 2 As shown in the figure, the cube represents the patient, the light source point of the first viewing angle (0°) is A, the light source point of the second viewing angle (90°) is C, point B is the two-dimensional pixel target point obtained from the first viewing angle (corresponding to a point on the receiving end detection plate of the C-arm X-ray machine), and point D is the two-dimensional pixel target point obtained from the second viewing angle. Since the distance from the light source point to the patient in the image parameters is only the distance from the light source point to the patient's skin surface, not the distance to the tumor in the body, after the light source (such as X-ray) penetrates the human body, the image formed on the receiving end (such as the detection plate of the C-arm X-ray machine) can often only reflect the projection position on the skin surface, rather than the real position of the lesion in the body. Therefore, the two-dimensional pixel target points (such as points B and D) directly obtained from the image are often only the projection of the lesion on the skin surface, rather than the lesion itself. The target point obtained from the first viewing angle is E, and the target point obtained from the second viewing angle is F, that is, the target points E and F are also just points on the skin surface, and the real target is located on the line segment or extension line between the light source and the initial target point. Therefore, the initial target point E and point F need to be processed again. Point A and point E need to be connected to obtain the first connection line, and point C and point F need to be connected to obtain the second connection line.

[0079] Furthermore, since point B and point D are the target points of the pixel image obtained by projecting X-rays emitted by the light source point through the human body to the detection board at the receiving end, point B is on the extension line of the first connecting line, and point D is on the extension line of the second connecting line. Then, the equations of the first connecting line and the second connecting line are as follows:

[0080] ;

[0081] ;

[0082] in, represents the line equation of the first line, represents the line equation of the second line, A represents the 3D world coordinates of the light source point on the first line, B represents the 3D world coordinates to be processed of the target point on the first line, C represents the 3D world coordinates of the light source point on the second line, and D represents the 3D world coordinates to be processed of the target point on the second line. represents the parameters on the first line, Indicates the parameters on the second wire.

[0083] in,

[0084] ;

[0085] ;

[0086] The equation construction matrix is ​​as follows:

[0087] ;

[0088] Solve the basic form of PX=Q by the least square method and get:

[0089] ;

[0090] in,

[0091] ;

[0092] ;

[0093] in, is the 3D world coordinate of the light source point on the first line, ( is the 3D world coordinate of the target point on the first line to be processed, ( is the 3D world coordinate of the light source point on the second line, ( ) is the 3D world coordinate of the target point on the second line to be processed.

[0094] After solving i and j according to the above formula, substitute , Two equations, we can get the points on the two connecting lines, which is Figure 3 The midpoint of the two points is the closest point to the two lines. Figure 2 Point G is the initial target point, and its coordinates will be used as the three-dimensional world coordinates of the initial target point.

[0095] Since the lesion is located in the body, it must be located at a certain position of the two lines or their extension lines. In order to find an estimated position closer to the lesion, this embodiment adopts a method of taking the point closest to the two lines at the same time as the target point. This method is based on the assumption that the distance between the lesion and the two lines is equal (or at least very close). By constructing the line equation and solving it by the least square method, a pair of points (located on the two lines respectively) can be found, and their distances to the midpoint are equal (or closest to being equal). This midpoint is the target point we are looking for, and it is closer to the actual position of the lesion. This method not only takes into account the distance from the light source point to the patient's skin surface, but also solves through the intersection of the lines, further improving the accuracy of the target point positioning.

[0096] Further, according to step S2133, Figure 3The two lines in the middle and the closest point of the two lines in space are found. This point is the closest position to both lines, but it is still a certain distance from the two lines. If the distance can be reduced, the closest point of the two lines in space can be found again. The error will be smaller and the coordinates will be more accurate. The positioning accuracy of the current solution is within 5mm compared with the gold standard. This method is suitable for situations where the two lines in space have intersections or no intersections. However, in actual solutions, the two lines basically have no intersections in space. The reasons for this phenomenon include errors in picking up two-dimensional coordinates on perspective views and errors in DICOM's own tag values.

[0097] Therefore, after obtaining the three-dimensional world coordinates of the initial target point in step S21, the image parameters need to be updated. The image parameters updated in step S22 are the distance SOD from the light source point to the patient and the pixel spacing spacing in the imaging system. The distance from the light source point to the plane where the world coordinate point G obtained in step S21 is located is calculated to obtain SOD', which should be accurately called the distance from the light source point to the target plane. Then, based on SID and spacing, the similar triangle formula is used to obtain the corresponding spacing' under the new SOD'. Therefore, step S22 updates the image parameters of the medical fluoroscopic image according to the three-dimensional world coordinates of the initial target point, including:

[0098] The distance from the light source point to the plane where the target point is located in the imaging system is calculated according to the three-dimensional world coordinates of the initial target point, and the distance SOD' from the light source point to the patient target plane in the imaging system is obtained.

[0099] The updated pixel spacing' is obtained by calculating the distance from the light source point to the detection board and the pixel spacing in the imaging system.

[0100] This embodiment first determines the position of the tumor target in the patient's body based on the three-dimensional world coordinates of the target point initially obtained. Since the original distance SOD from the light source to the patient is measured to the patient, there is a certain deviation from the tumor target in the patient's body. Therefore, this embodiment calculates the distance SOD' from the light source to the plane where the target is located based on the three-dimensional world coordinates of the target, thereby replacing the original distance SOD from the light source to the patient. At the same time, in order to maintain the consistency of the image parameters, it is also necessary to update the corresponding pixel spacing spacing' based on the new SOD' value and the SID (the distance from the light source to the image receiver) of the imaging system and the original pixel spacing using the principle of similar triangles. This optimization step significantly improves the accuracy of positioning from two-dimensional perspective images to three-dimensional space, ensures the accuracy of positioning key structures such as target points, and provides more reliable information support for subsequent medical diagnosis and treatment.

[0101] Furthermore, in step S23, calculation is performed based on the two-dimensional pixel coordinates and the updated image parameters to obtain the three-dimensional world coordinates of the actual target point, including:

[0102] S231, calculating a target coordinate conversion matrix according to the updated image parameters, wherein the target coordinate conversion matrix is ​​used to convert the two-dimensional pixel coordinates of the target point into three-dimensional world coordinates, wherein the target coordinate conversion matrix is ​​composed of conversion parameters of a two-dimensional pixel coordinate system, a two-dimensional image coordinate system, a three-dimensional camera coordinate system, and a three-dimensional world coordinate system. The calculation logic of the target coordinate conversion matrix is ​​the same as that of the initial target coordinate conversion matrix mentioned above, and will not be repeated here.

[0103] S232, bringing the two-dimensional pixel coordinates of the target point of the dual perspectives into the target coordinate conversion matrix, and calculating and obtaining the three-dimensional world coordinates of the target point after updating of the dual perspectives.

[0104] S233, processing and calculating according to the updated target point and the three-dimensional world coordinates of the dual perspectives to obtain the three-dimensional world coordinates of the actual target point of the dual perspectives.

[0105] The calculation logic of the 3D world coordinates of the actual target point in step S233 is the same as that of the 3D world coordinates of the initial target point in step S213, which can be specifically:

[0106] The light source points of the dual-view are obtained as point A' and point C', and then point A' and point C' are connected with the updated target points (point E' and point F') respectively, and the following is obtained: Figure 3 Connect the two solid lines in , and the midpoint of the two points is the spatial point closest to the two lines, and its coordinates will be used as the three-dimensional world coordinates of the actual target point.

[0107] In one embodiment, the three-dimensional world coordinates of the rotation center of the imaging system are calculated according to the three-dimensional world coordinates of the light source point and the three-dimensional world coordinates of the target point in step S4, including:

[0108] S41, drawing a first projection path line according to the three-dimensional world coordinates of the light source point of the first viewing angle and the three-dimensional world coordinates of the actual target point;

[0109] S42, drawing a second projection path line according to the three-dimensional world coordinates of the light source point at the second viewing angle and the three-dimensional world coordinates of the actual target point;

[0110] S43, selecting a common point on the first projection path line and the second projection path line as a rotation center, and calculating the three-dimensional world coordinates of the rotation center.

[0111] This embodiment calculates the three-dimensional world coordinates of the rotation center of the imaging system, and then calculates the three-dimensional world coordinate error vector between the rotation center and the target point, so as to place the target point at the center of the two-dimensional medical fluoroscopic image, that is, the area to be observed can be in the exact center of the two-dimensional medical fluoroscopic image, so that the light source can vertically illuminate the target. When the projection of the target is located at the center of the two-dimensional medical fluoroscopic image, the projection light will be vertically irradiated onto the imaging plane along the optical axis, thereby reducing image distortion caused by factors such as lens distortion, which helps to ensure that the irradiation field in the radiotherapy plan is consistent with the actual irradiation situation.

[0112] The embodiment of the present invention further provides a method for correcting positioning errors, which is performed by a doctor or a technician and specifically includes:

[0113] For the treatment bed and the patient that have been positioned according to the three-dimensional coordinates in the surgical plan, a preoperative two-dimensional medical perspective image is taken, and an error vector is obtained using the above surgical positioning error calculation method;

[0114] The light source system and / or the treatment couch in the imaging system are moved according to the error vector so that the target point is located at the center of the projected image.

[0115] Specifically, based on the patient's CT or other imaging data, the doctor will develop a detailed treatment plan on the computer, including the three-dimensional coordinates of the target area, the treatment dose, etc. Then, based on the three-dimensional coordinates in the medical plan, the technician or doctor will adjust the patient's treatment bed so that the patient's target area (lesion) is as close to the planned position as possible. However, due to various factors (such as changes in patient position, equipment accuracy limitations, etc.), there is usually a certain error; therefore, after the initial positioning, the C-arm is used to take a perspective image of the patient, and the CBCT image obtained is used to obtain the current actual three-dimensional coordinates of the target tumor lesion in the patient's body; a vertical irradiation projection system is constructed based on the light source point, and the actual three-dimensional coordinates obtained by the CBCT are judged to be located at the center of the canvas of the vertical irradiation projection system, and the error vector (size and direction) is calculated using the surgical positioning error calculation method. Finally, based on the results of the error evaluation, the technician or doctor will adjust the light source system and / or the patient's treatment bed in the imaging system again to eliminate or reduce the positioning error. This method can be used in the fields of puncture, ablation and radiotherapy.

[0116] like Figure 4 This is a schematic diagram of a moving light source system. By moving the light source point according to the error vector and keeping the patient treatment bed (the target point in the patient's body) stationary, the projection of the target tumor lesion can be located at the center of the projection image. Figure 5 This is a schematic diagram of a treatment bed for moving a patient. The position of the treatment bed for the patient is moved according to the error vector, and the light source system (light source point) remains stationary, so that the projection of the target tumor lesion is located at the center of the projection image.

[0117] In this embodiment, adjusting the light source system and / or the patient's treatment bed according to the error vector has advantages in accuracy, safety and repeatability compared to temporarily changing the surgical plan. Therefore, in radiotherapy practice, when it is found that there is a large error between the actual position of the patient and the position in the medical plan, it is usually preferred to determine and correct the error through image registration rather than directly changing the surgical plan. This can ensure the accuracy of the radiotherapy process, that is, ensure that the treatment rays are accurately focused on the target area while minimizing damage to surrounding healthy tissues. In addition, determining and correcting errors through image registration can also improve the safety of treatment and avoid the uncertainty and risks that may be caused by directly modifying the surgical plan. Finally, this method also has good repeatability, which can ensure that in future radiotherapy processes, the patient can maintain a position consistent with the planned image, thereby further improving the stability and effect of the treatment.

[0118] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0119] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0120] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0121] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0122] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for calculating surgical positioning error, characterized in that: include: Acquire a preoperative two-dimensional medical perspective image of the patient and two-dimensional pixel coordinates and image parameters of a target point therein, wherein the image parameters include basic properties of the medical perspective image and geometric parameters of an imaging system, wherein the two-dimensional medical perspective image is a perspective image taken at any two different viewing angles, wherein an angle between a first viewing angle and a second viewing angle is between 30° and 150°; Calculate the three-dimensional world coordinates of the initial target point according to the two-dimensional pixel coordinates and the image parameters; updating the image parameters of the medical fluoroscopic image according to the three-dimensional world coordinates of the initial target point; Calculate according to the two-dimensional pixel coordinates and the updated image parameters to obtain the three-dimensional world coordinates of the actual target point; Using the target coordinate transformation matrix, the three-dimensional world coordinates of the light source point are calculated; Draw a first projection path line according to the three-dimensional world coordinates of the light source point of the first viewing angle and the three-dimensional world coordinates of the actual target point; Draw a second projection path line according to the three-dimensional world coordinates of the light source point of the second viewing angle and the three-dimensional world coordinates of the actual target point; Selecting a common point on the first projection path line and the second projection path line as a rotation center, and calculating the three-dimensional world coordinates of the rotation center; An error vector between the three-dimensional world coordinates of the rotation center and the three-dimensional world coordinates of the actual target point is calculated.

2. The method according to claim 1, characterized in that The image parameters include image resolution of the medical fluoroscopic image, pixel spacing, distance from the light source point to the patient in the imaging system, distance from the light source point to the detection plate in the imaging system, first angle, second angle, first angle increment, and second angle increment.

3. The method according to claim 1, characterized in that Calculating the three-dimensional world coordinates of the initial target point according to the two-dimensional pixel coordinates and the image parameters includes: Calculating an initial target coordinate conversion matrix according to the image parameters, the initial target coordinate conversion matrix is ​​used to convert the two-dimensional pixel coordinates of the target point into three-dimensional world coordinates, wherein the initial target coordinate conversion matrix is ​​composed of conversion parameters of a two-dimensional pixel coordinate system, a two-dimensional image coordinate system, a three-dimensional camera coordinate system, and a three-dimensional world coordinate system; Substituting the two-dimensional pixel coordinates of the target point of the dual-view into the initial target coordinate conversion matrix, and calculating the to-be-processed three-dimensional world coordinates of the target point of the dual-view; Processing and calculation are performed according to the target point of the dual perspectives and the three-dimensional world coordinates to be processed to obtain the three-dimensional world coordinates of the initial target point of the dual perspectives.

4. The method according to claim 2, characterized in that: Updating the image parameters of the medical fluoroscopic image according to the three-dimensional world coordinates of the initial target point includes: The distance from the light source point to the plane where the target point is located in the imaging system is calculated according to the three-dimensional world coordinates of the initial target point, and the distance from the light source point to the patient target plane in the imaging system is obtained; The updated pixel pitch is obtained by performing calculation based on the distance from the light source point to the detection plate in the imaging system and the pixel pitch.

5. The method according to claim 1, characterized in that Calculating according to the two-dimensional pixel coordinates and the updated image parameters to obtain the three-dimensional world coordinates of the actual target point includes: Calculate a target coordinate conversion matrix according to the updated image parameters, wherein the target coordinate conversion matrix is ​​used to convert the two-dimensional pixel coordinates of the target point into three-dimensional world coordinates, wherein the target coordinate conversion matrix is ​​composed of conversion parameters of a two-dimensional pixel coordinate system, a two-dimensional image coordinate system, a three-dimensional camera coordinate system, and a three-dimensional world coordinate system; The two-dimensional pixel coordinates of the target point of the dual-viewing angle are brought into the target coordinate transformation matrix to calculate the three-dimensional world coordinates of the target point after updating the dual-viewing angle; Processing and calculation are performed based on the updated target points and three-dimensional world coordinates of the dual perspectives to obtain the three-dimensional world coordinates of the actual target points of the dual perspectives.

6. A surgical positioning error calculation device, characterized in that: include: A processor and a memory connected to the processor; wherein the memory stores instructions executable by the processor, and the instructions are executed by the processor so that the processor executes the surgical positioning error calculation method as described in any one of claims 1-5.

7. A method for correcting positioning errors, characterized in that: include: For the treatment bed and the patient positioned according to the three-dimensional coordinates in the surgical plan, a preoperative two-dimensional medical perspective image is taken, and an error vector is obtained using the method described in any one of claims 1 to 5; The light source system and / or the treatment couch in the imaging system is moved according to the error vector so that the target point is located at the center of the projected image.

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