A Spatial Location Method and Device for X-ray Images Based on a Navigation Scale

Abstract

The present invention discloses a spatial positioning method and device for X-ray images based on a navigation ruler, which relates to the field of medical device technology, including: obtaining an anteroposterior X-ray image and a lateral X-ray image when a surgical navigation ruler is in a closed state; extracting double circular ring features and straight line features corresponding to a first circular portion, a second circular portion, and a line segment portion in the two X-ray images respectively; solving the parameter values of an imaging model of an X-ray imaging device based on the double circular ring features and straight line features; the imaging model of the X-ray imaging device represents the transformation relationship between a world coordinate system and a screen coordinate system; and calculating the three-dimensional coordinate value of the point to be positioned in space in the world coordinate system based on the coordinate values of the point to be positioned projected onto the anteroposterior X-ray image and the lateral X-ray image and the parameter values of the imaging model of the X-ray imaging device. The present invention can obtain three-dimensional information of an object and realize spatial positioning of the object through two X-ray images, which is more accurate and convenient.

Description

Technical Field

[0001] The present invention relates to the technical field of surgical navigation positioning technology, and in particular to a spatial positioning method and device for X-ray images based on a navigation scale. Background Art

[0002] Minimally invasive orthopedic surgeries often use X-ray images generated by intraoperative C-arm fluoroscopy to obtain the patient's anatomical information, thereby performing puncture positioning and ensuring that surgical instruments safely reach the patient's target surgical area. However, X-ray images are two-dimensional images, and a single X-ray image cannot provide sufficient information to determine the optimal positioning depth, positioning angle, and other parameters required for positioning. Therefore, orthopedic surgeons often perform fluoroscopy on the patient from multiple angles to supplement the target position information required by the doctor. Despite this, this method still places high demands on the doctor's spatial imagination ability. Therefore, for young doctors, this method has an extremely steep learning curve.

[0003] With advances in science and technology, 3D C-arms and O-arms have emerged as intraoperative devices. These provide doctors with 3D anatomical information directly during surgery, effectively solving the aforementioned problem. However, 3D C-arms and O-arms are expensive, making them available only to a few large hospitals. Most hospitals, especially those at the grassroots level, still rely on multi-angle 2D X-rays for positioning. Positioning using two X-ray images has a wide range of applications and great value. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the prior art, the present invention provides a method and device for spatial positioning of X-ray images based on a navigation scale, which can solve the above-mentioned technical problems.

[0005] One aspect of the present invention provides a method for spatial positioning of an X-ray image based on a navigation scale, the method comprising:

[0006] When the surgical navigation ruler is in a closed state, the surgical navigation ruler comprises a first circular portion, a second circular portion, and a line segment portion that can be imaged by a medical imaging device; wherein the first circular portion and the second circular portion are coaxial, the diameter of the first circular portion is smaller than the diameter of the second circular portion, and the line segment portion extends along the radial direction of the first circular portion;

[0007] The spatial positioning method of the X-ray image comprises the following steps:

[0008] Acquire an anteroposterior X-ray image and a lateral X-ray image when the surgical navigation ruler is in a closed state;

[0009] Extracting double circular ring features and straight line features corresponding to the first circular portion, the second circular portion, and the line segment portion in the two X-ray images respectively;

[0010] Solving parameter values of an imaging model of an X-ray imaging device based on the double-circle feature and the straight line feature; the imaging model of the X-ray imaging device represents a transformation relationship between a world coordinate system and a screen coordinate system;

[0011] The three-dimensional coordinate value of the point to be positioned in the space is calculated in the world coordinate system according to the coordinate value of the point to be positioned in the space projected onto the anteroposterior X-ray image and the lateral X-ray image and the parameter value of the imaging model of the X-ray imaging device.

[0012] Furthermore, the spatial positioning method of an X-ray image based on a navigation scale further includes:

[0013] Take any position in the X-ray imaging environment as the origin of the world coordinate system;

[0014] The radiation source of the X-ray imaging device is used as the origin of the coordinate system of the X-ray imaging device;

[0015] The two-dimensional projection of the object in the X-ray imaging environment through the X-ray imaging device and a certain plane is used as the image coordinate system, and the intersection of the optical axis and the image plane is used as the origin of the image coordinate system;

[0016] Presenting the image information converted by the two-dimensional projection on a computer screen, and using the two-dimensional coordinate system on the screen as a screen coordinate system;

[0017] The coordinate transformation relationship among the world coordinate system, the X-ray imaging device coordinate system, the image coordinate system and the screen coordinate system is calculated to construct an imaging model of the X-ray imaging device.

[0018] Furthermore, the spatial positioning method of an X-ray image based on a navigation scale further includes:

[0019] Taking the origin of the X-ray imaging device coordinate system as the optical center and aligning the z-axis of the X-ray imaging device coordinate system with the optical axis, the coordinate relationship between the point to be located in space in the world coordinate system and the X-ray imaging device coordinate system is calculated by the following formula:

[0020]

[0021]

[0022]

[0023] Among them, t x , t y , t zis the translation component between the two coordinates, α, β, γ are the rotation components between the two coordinate systems, x, y, z are the three-dimensional coordinates of the point to be located in space in the coordinate system of the X-ray imaging device, and X, Y, Z are the three-dimensional coordinates of the point to be located in space in the world coordinate system.

[0024] Furthermore, the spatial positioning method of an X-ray image based on a navigation scale further includes:

[0025] Let the x and y axes of the X-ray imaging device coordinate system be parallel to the horizontal and vertical axes of the image coordinate system, and calculate the projection position coordinates of the point to be located in the space in the image coordinate system by the following formula:

[0026]

[0027]

[0028] Wherein, u' and v' are the horizontal coordinate and vertical coordinate of the projection position of the point to be located in space in the image coordinate system, and f is the focal length of the X-ray imaging device.

[0029] Furthermore, the spatial positioning method of an X-ray image based on a navigation scale further includes:

[0030] The coordinate value of the point to be located in the space in the screen coordinate system is calculated by the following formula:

[0031]

[0032]

[0033] Among them, u and v are the horizontal and vertical coordinate values of the point to be located in the space in the screen coordinate system, u0 and v0 are the horizontal and vertical coordinate values of the origin of the image coordinate system in the screen coordinate system, dx is the actual horizontal axis size corresponding to the screen pixel, and dy is the actual vertical axis size corresponding to the screen pixel.

[0034] Furthermore, the spatial positioning method of an X-ray image based on a navigation scale further includes:

[0035] Combining the above relationships, we get the transformation relationship from the world coordinate system to the screen coordinate system:

[0036]

[0037] Furthermore, the spatial positioning method of an X-ray image based on a navigation scale further includes:

[0038] According to the above transformation relationship from the world coordinate system to the screen coordinate system, the imaging model of the X-ray imaging device is obtained:

[0039]

[0040]

[0041] The equation of the space line corresponding to a point in the image coordinate system:

[0042]

[0043] in,

[0044] Furthermore, the spatial positioning method of an X-ray image based on a navigation scale, obtaining mathematical expressions of the double-circle feature and the straight line feature in different coordinate systems, includes:

[0045] The analytical equation of the space straight line in the coordinate system of the X-ray imaging device is obtained as:

[0046]

[0047] Among them, e1, e2, h1, and h2 are the standard parameters of the spatial straight line equation in the coordinate system of the X-ray imaging device;

[0048] The analytical equation for the projection of the spatial straight line in the X-ray imaging device coordinate system onto the image coordinate system is:

[0049] e3u+m3v=n3

[0050] Among them, e3, m3, and n3 are the standard parameters of the analytical equation of the projection of the spatial straight line in the X-ray imaging device coordinate system onto the image coordinate system;

[0051] The analytical equation of the circle in the X-ray imaging device coordinate system is obtained as:

[0052]

[0053] Wherein, a, b, and c are the standard parameters of the analytical equation of the circle in the coordinate system of the X-ray imaging device;

[0054] The analytical equation for obtaining the projection of the circle in the X-ray imaging device coordinate system onto the image coordinate system is:

[0055] d(u) 2 +e(v) 2 +fuv+gu+hv+j=0

[0056] Wherein, d(u) represents the transformation function of the horizontal coordinate of the X-ray imaging device coordinate system projected onto the image coordinate system, e(v) represents the transformation function of the vertical coordinate of the X-ray imaging device coordinate system projected onto the image coordinate system, and g, h, and j represent the standard parameters of the analytical equation of the circle in the X-ray imaging device coordinate system projected onto the image coordinate system.

[0057] The above equations are combined with the imaging model of the X-ray imaging device to calculate the parameter values A1 to A 11 .

[0058] Furthermore, the spatial positioning method of an X-ray image based on a navigation scale calculates the spatial straight line corresponding to the coordinate value of the point to be positioned in space projected onto the anteroposterior X-ray image and the lateral X-ray image according to the spatial straight line equation corresponding to a point on the image coordinate system;

[0059] The midpoint coordinates of the common perpendicular lines of the two spatial straight lines are used as the three-dimensional coordinates of the point to be located in the world coordinate system.

[0060] Another aspect of the present invention provides a spatial positioning device for X-ray images based on a navigation scale, comprising:

[0061] A surgical navigation ruler, when in a closed state, comprises a first circular portion, a second circular portion, and a line segment portion that can be imaged by a medical imaging device; wherein the first circular portion and the second circular portion are coaxial, the diameter of the first circular portion is smaller than the diameter of the second circular portion, and the line segment portion extends along the radial direction of the first circular portion;

[0062] And spatial positioning modules, including:

[0063] An image acquisition unit, used for acquiring an anteroposterior X-ray image and a lateral X-ray image when the surgical navigation scale is in a closed state;

[0064] a feature extraction unit for respectively extracting double circular ring features and straight line features corresponding to the first circular portion, the second circular portion, and the line segment portion in the two X-ray images;

[0065] a parameter calculation unit, configured to solve parameter values of an imaging model of an X-ray imaging device based on the double-circle feature and the straight line feature; the imaging model of the X-ray imaging device represents a transformation relationship between a world coordinate system and a screen coordinate system;

[0066] The coordinate calculation unit is used to calculate the three-dimensional coordinate value of the point to be located in the space in the world coordinate system based on the coordinate value of the point to be located in the space projected onto the frontal X-ray image and the lateral X-ray image and the parameter value of the imaging model of the X-ray imaging device.

[0067] The present application provides a method and device for spatial positioning of X-ray images based on a navigation scale, which does not require the use of expensive equipment and can quickly and accurately achieve spatial positioning of the photographed object using only two X-ray images at different angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0069] Figure 1 This is a workflow diagram for achieving spatial positioning using two X-ray images provided in one embodiment of the present application;

[0070] Figure 2 This is a schematic diagram of a coordinate system provided by an embodiment of the present application;

[0071] Figure 3 This is a flowchart of a method for spatial positioning of X-ray images based on a navigation scale provided by one embodiment of the present application;

[0072] Figure 4 This is a diagram of the surgical navigation scale structure provided by one embodiment of the present application;

[0073] Figure 5 is a view of anterior and lateral X-ray images provided by one embodiment of the present application;

[0074] Figure 6 This is a schematic diagram of extracting double-circle features and straight line features from an X-ray image provided by an embodiment of the present application;

[0075] Figure 7 This is a schematic diagram of the transformation relationship between coordinate systems provided by an embodiment of the present application;

[0076] Figure 8 This is a schematic diagram of obtaining three-dimensional points of an object provided by an embodiment of the present application;

[0077] Figure 9 It is a structural diagram of a spatial positioning device for X-ray images based on a navigation scale provided in one embodiment of the present application. DETAILED DESCRIPTION

[0078] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0079] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0080] It should be understood that although the terms first, second, third, etc. may be used to describe the acquisition modules in the embodiments of the present invention, the acquisition modules should not be limited to these terms. These terms are only used to distinguish the acquisition modules from each other.

[0081] The word "if," as used herein, may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0082] It should be noted that the directional terms such as "upper," "lower," "left," and "right" described in the embodiments of the present invention are described from the perspectives shown in the accompanying drawings and should not be construed as limiting the embodiments of the present invention. Furthermore, in the context, it should be understood that when an element is referred to as being formed "on" or "under" another element, it can be formed not only directly "on" or "under" the other element, but also indirectly "on" or "under" the other element through an intermediate element.

[0083] In minimally invasive orthopedic surgery, X-ray images generated by C-arm fluoroscopy are needed to obtain patient anatomical information in order to accurately locate the puncture. In this environment, there are several contradictions: a single X-ray image is not enough to provide enough information to determine the optimal positioning parameters; multi-angle fluoroscopy requires high spatial imagination, and the learning curve for young doctors is extremely steep; three-dimensional C-arms and O-arms can directly provide patients with three-dimensional anatomical information, but they are expensive and only a few large hospitals can equip them. The present invention realizes spatial positioning through two X-ray images, which has positive significance for most hospitals, especially grassroots hospitals, that still use multi-angle two-dimensional X-ray images to achieve positioning. It can more conveniently and accurately achieve spatial positioning and obtain patient anatomical information.

[0084] Reference below Figure 1 , describes the overall workflow of intraoperative C-arm acquisition of two X-ray images for spatial positioning. Figure 1As shown, first, the anteroposterior and lateral X-ray images collected by the C-arm are acquired; then, the graphic features of the surgical navigation scale projection imaging in the two X-ray images are extracted; then, the imaging model parameters of the constructed X-ray imaging device are calculated based on the extracted graphic features; finally, the spatial coordinate values of the point to be located in space can be calculated based on the coordinate values projected onto the anteroposterior and lateral X-ray images and the imaging model of the X-ray imaging device.

[0085] Among them, constructing the imaging model of the X-ray imaging device involves four coordinate systems: the world coordinate system, the X-ray imaging device coordinate system, the image coordinate system, and the screen coordinate system. Figure 2 The world coordinate system is a coordinate system constructed by selecting any position in the X-ray imaging environment as the origin, which can describe the position of the X-ray imaging device and the position of any other object in the environment; the X-ray imaging device coordinate system is a coordinate system constructed with the radiation source of the X-ray imaging device as the origin; the image coordinate system is the two-dimensional projection of the object in the X-ray imaging environment through the X-ray imaging device and a certain plane as the image coordinate system, and the intersection of the optical axis and the image plane is the origin of the image coordinate system; the screen coordinate system is the image information converted by the two-dimensional projection presented on the computer screen, and the two-dimensional coordinate system in the screen is the screen coordinate system.

[0086] See also Figure 3 , an embodiment of the present application provides a spatial positioning method of X-ray images based on a navigation scale.

[0087] Surgical navigation rulers are tools that assist in positioning medical imaging equipment. Figure 4 As shown, when the surgical navigation ruler is in a closed state, it includes a first circular portion, a second circular portion, and a linear portion that can be imaged by medical imaging equipment. The first circular portion and the second circular portion are coaxial, the diameter of the first circular portion is smaller than the diameter of the second circular portion, and the linear portion extends radially along the first circular portion.

[0088] The spatial positioning method of X-ray images comprises the following steps:

[0089] Step S101 , acquiring an anteroposterior X-ray image and a lateral X-ray image when the surgical navigation scale is in a closed state.

[0090] Specifically, the C-arm is used during surgery to acquire images, obtaining anteroposterior and lateral X-ray images when the surgical navigation scale is closed. For example, to capture anteroposterior and lateral X-ray images of the lumbar spine, an anteroposterior X-ray image is captured from the patient's anteroposterior position, and a lateral X-ray image is captured from the left and right positions. Figure 5 The acquired anteroposterior and lateral images contain images of the area to be positioned and the surgical navigation scale, wherein the circular portion becomes an ellipse after perspective projection, and the line segment portion remains a line segment after perspective projection.

[0091] In step S102 , double circular ring features and straight line features corresponding to the first circular portion, the second circular portion, and the line segment portion are extracted from the two X-ray images respectively.

[0092] Specifically, the extraction effect is as follows Figure 6 As shown, the mathematical expressions for obtaining the straight line feature and the double ring feature, i.e., the elliptical feature formed by projecting the two circular parts onto the screen coordinate system, in different coordinate systems include:

[0093] The analytical equation of the space straight line in the coordinate system of the X-ray imaging device is obtained as:

[0094]

[0095] Among them, e1, e2, h1, and h2 are the standard parameters of the spatial straight line equation in the coordinate system of the X-ray imaging device;

[0096] The analytical equation for the projection of the spatial straight line in the X-ray imaging device coordinate system onto the screen coordinate system is:

[0097] e3u+m3v=n3

[0098] Among them, e3, m3, and n3 are the standard parameters of the equation of the projection of the space line in the X-ray imaging device coordinate system onto the screen coordinate system;

[0099] The analytical equation of the circle in the X-ray imaging device coordinate system is obtained as:

[0100]

[0101] Wherein, a, b, and c are the standard parameters of the analytical equation of the circle in the coordinate system of the X-ray imaging device;

[0102] The analytical equation for the ellipse formed by the projection of a circle in the X-ray imaging device coordinate system in the screen coordinate system is:

[0103] d(u) 2 +e(v) 2 +fuv+gu+hv+j=0

[0104] Wherein, d(u) represents the transformation function of the horizontal coordinate of the X-ray imaging device coordinate system projected onto the screen coordinate system, e(v) represents the transformation function of the vertical coordinate of the X-ray imaging device coordinate system projected onto the screen coordinate system, and g, h, and j represent the standard parameters of the analytical equation of the ellipse projected from the circle in the X-ray imaging device coordinate system onto the screen coordinate system.

[0105] Step S103 , solving parameter values of an imaging model of an X-ray imaging device according to the double-circle feature and the straight line feature; the imaging model of the X-ray imaging device represents the transformation relationship between the world coordinate system and the screen coordinate system.

[0106] Specifically, the method is divided into two parts: constructing an imaging model of the X-ray imaging device and solving the parameter values of the imaging model.

[0107] Construct an imaging model of an X-ray imaging device:

[0108] Assume that there is a point P to be located in the environment, (X, Y, Z) is its coordinate in the world coordinate system; (x, y, z) is its coordinate in the coordinate system of the X-ray imaging device; (u', v') is its coordinate in the image coordinate system; (u, v) is its coordinate in the screen coordinate system. The imaging model of the X-ray imaging device represents the transformation relationship between the world coordinate system and the screen coordinate system. The point P in the world coordinate system is mapped to the corresponding point in the screen coordinate system through a series of coordinate transformations. The transformation process is as follows: Figure 7 As shown, constructing an imaging model of an X-ray imaging device requires calculating the transformation relationship between this series of coordinate systems.

[0109] For example, let's construct a C-arm imaging model. A C-arm X-ray machine is primarily composed of a C-frame, a tube that generates X-rays, an image intensifier, a CCD camera, and an image processing workstation. First, in the transformation from the world coordinate system to the X-ray imaging device coordinate system, the X-ray imaging device coordinate system uses the optical center of the camera as the origin, with the z-axis coinciding with the optical axis of the camera. The homogeneous coordinates of the point to be located P in the world coordinate system and the X-ray imaging device coordinate system are (X, Y, Z, 1) respectively. T 、(x,y,z,1) T The coordinate transformation relationship of point P in the world coordinate system and the X-ray imaging device coordinate system is:

[0110]

[0111] is the rotation matrix, we have:

[0112]

[0113] Among them, t x , t y , t z is the translation component between the two coordinates, and α, β, and γ are the rotation components between the two coordinate systems.

[0114] Secondly, in the transformation from the X-ray imaging device coordinate system to the image coordinate system, the x and y axes of the X-ray imaging device coordinate system are parallel to the horizontal and vertical axes of the image coordinate system. The projection position P' of point P on the image is the intersection of the line connecting the optical center and P and the image plane. The coordinates of the projection position P' in the image coordinate system are then:

[0115]

[0116]

[0117] Where u' and v' are the horizontal and vertical coordinates of the projection position of point P in the image coordinate system, and f is the focal length of the X-ray imaging device. It is expressed as a homogeneous matrix as follows:

[0118]

[0119] Then, in the transformation from the image coordinate system to the screen coordinate system, an M×N pixel image can be stored in a computer as an M×N two-dimensional array. Each number in the array is mapped one-to-one to the pixels on the screen. The coordinates of each pixel on the screen are the row and column numbers of the pixel in the array. These coordinates have no clear physical meaning, so the units of the screen coordinates are converted into physical units. dx is the actual horizontal axis size corresponding to the screen pixel, and dy is the actual vertical axis size corresponding to the screen pixel. In the image coordinate system, the origin of the coordinate system is defined as the intersection of the optical axis of the camera and the image plane. However, due to camera manufacturing reasons, there will be some deviation. Assuming that the coordinates of the origin of the image coordinate system in the screen coordinate system are (u0, v0), and the coordinates of point P in the screen coordinate system are (u, v), then the transformation relationship of point P from the image coordinate system to the screen coordinate system is:

[0120]

[0121]

[0122] The form expressed as a homogeneous matrix is as follows:

[0123]

[0124] By combining the transformation relations between the above coordinate systems and the homogeneous matrix, we can get the transformation relation from the world coordinate system to the screen coordinate system:

[0125]

[0126] Finally, the imaging model of the C-arm can be obtained by expanding the above transformation relationship:

[0127]

[0128]

[0129] The equation of the space line corresponding to a point in the image coordinate system:

[0130]

[0131] in,

[0132] Solve for the parameter values of the imaging model:

[0133] The linear characteristic equation obtained in step S102 is combined with the imaging model of the C-arm obtained in the above part to obtain the final form: F1(A)x+F2(A)=0. This formula is always valid, so two quadratic equations are obtained: F1(A)=0, F2(A)=0.

[0134] The double-ring feature obtained in step S102, i.e., the elliptical feature equation, is combined with the imaging model of the C-arm to obtain the final form: F3(A)x 2 +F4(A)y 2 +F5(A)xy+F6(A)x+F7(A)y+F8(A)=0, this formula is always true, so we get 5 quadratic equations: F3(A) / F8(A)=1 / c, F4(A) / F8(A)=1 / c, F5(A)=0, F6(A) / F8(A)=a / c, F7(A) / F8(A)=b / c, and the same applies to large and small ellipses, so we can get 10 quadratic equations.

[0135] According to the obtained double-circle feature and straight line feature combined with the C-arm imaging model, a total of 12 quadratic equations can be formed, including A1 to A 11 There are 11 unknown parameters in total, which means that the imaging model parameter values can be calculated.

[0136] For example, after taking an X-ray image in the frontal and lateral positions, the C-arm imaging model is solved based on the double-circle feature and straight line feature in the image to obtain A 1正位 、A 2正位 …A 11正位 , A 1侧位 、A 2侧位 …A 11侧位 .

[0137] Step S104 , calculating the three-dimensional coordinate value of the point to be positioned in the world coordinate system according to the coordinate value of the point to be positioned in the space projected onto the anteroposterior X-ray image and the lateral X-ray image and the parameter value of the imaging model of the X-ray imaging device.

[0138] Specifically, based on the spatial line equation corresponding to the point on the screen image obtained in step S103, the spatial lines corresponding to the coordinate values of the point to be located in space projected onto the anteroposterior X-ray image and the lateral X-ray image are calculated. The coordinates of the midpoint of the common perpendicular line between the two spatial lines are used as the three-dimensional coordinates of the point to be located in the world coordinate system.

[0139] For example: See Figure 8 , select the coordinates of the object projected onto the front and side X-ray images at the same three-dimensional point, and obtain (u 正位 ,v正位 )、(u 侧位 ,v 侧位 ), respectively substitute the spatial straight line equation corresponding to a point on the screen image, and two spatial straight lines can be obtained, one in the orthogonal direction and the other in the lateral direction, passing through this three-dimensional point of the object. The spatial straight line in the orthogonal direction is the only straight line determined by the optical center of the camera and this three-dimensional point of the object when the C-arm is in the orthogonal position; the spatial straight line in the lateral direction is the only straight line determined by the optical center of the camera and this three-dimensional point of the object when the C-arm is in the lateral position. Ideally, these two spatial straight lines are intersecting, and the coordinates of this intersection are the coordinates of this three-dimensional point of the object. However, in actual situations, there may be errors that make the two spatial straight lines not intersect. Therefore, the three-dimensional coordinates of the midpoint of the common perpendicular line of the two spatial straight lines, that is, the three-dimensional coordinates of a point in space that is equal and shortest distance away from the two spatial straight lines, are selected as the three-dimensional coordinates of the selected three-dimensional point of the object in the world coordinate system, thereby completing spatial positioning.

[0140] The above-mentioned spatial positioning method of X-ray images based on navigation scales in this embodiment can obtain three-dimensional information of an object through two X-ray images and realize spatial positioning of the object, thereby simplifying the conventional multi-angle two-dimensional X-ray image positioning method.

[0141] See also Figure 9 Another embodiment of the present invention further provides a navigation scale-based X-ray image spatial positioning device 900, comprising a surgical navigation scale 910 and a spatial positioning module 920. The spatial positioning module 920 includes an image acquisition unit 921, a feature extraction unit 922, a parameter calculation unit 923, and a coordinate calculation unit 924. The navigation scale-based X-ray image spatial positioning device 900 is configured to perform the steps of the aforementioned method embodiment.

[0142] Specifically, the spatial positioning device 900 of the X-ray image based on the navigation scale includes:

[0143] The surgical navigation ruler 910, when in a closed state, comprises a first circular portion, a second circular portion, and a line segment portion that can be imaged by a medical imaging device; wherein the first circular portion and the second circular portion are coaxial, the diameter of the first circular portion is smaller than the diameter of the second circular portion, and the line segment portion extends radially along the first circular portion;

[0144] The spatial positioning module 920 includes:

[0145] An image acquisition unit 921 is configured to acquire an anteroposterior X-ray image and a lateral X-ray image when the surgical navigation scale is in a closed state;

[0146] The feature extraction unit 922 is configured to extract double circular features and straight line features corresponding to the first circular portion, the second circular portion, and the line segment portion in the two X-ray images, respectively;

[0147] A parameter calculation unit 923 is configured to solve parameter values of an imaging model of an X-ray imaging device based on the double-circle feature and the straight line feature; the imaging model of the X-ray imaging device represents a transformation relationship between a world coordinate system and a screen coordinate system;

[0148] The coordinate calculation unit 924 is configured to calculate the three-dimensional coordinate value of the point to be positioned in the world coordinate system based on the coordinate value of the point to be positioned in the space projected onto the anterior X-ray image and the lateral X-ray image and the parameter value of the imaging model of the X-ray imaging device.

[0149] It should be noted that the spatial positioning device 900 for X-ray images based on the navigation scale provided in this embodiment corresponds to a technical solution that can be used to execute various method embodiments. Its implementation principle and technical effects are similar to those of the method and will not be repeated here.

[0150] The above description is merely a preferred embodiment of the present invention. Those skilled in the art should understand that the scope of disclosure involved in the present invention is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also includes other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the above-mentioned disclosed concepts. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in the present invention.

Claims

1. A spatial positioning method for X-ray images based on a navigation scale, characterized in that: When the surgical navigation ruler is in a closed state, the surgical navigation ruler comprises a first circular portion, a second circular portion, and a line segment portion that can be imaged by a medical imaging device; wherein the first circular portion and the second circular portion are coaxial, the diameter of the first circular portion is smaller than the diameter of the second circular portion, and the line segment portion extends along the radial direction of the first circular portion; The spatial positioning method of the X-ray image comprises the following steps: Acquire an anteroposterior X-ray image and a lateral X-ray image when the surgical navigation ruler is in a closed state; Extracting double circular ring features and straight line features corresponding to the first circular portion, the second circular portion, and the line segment portion in the two X-ray images respectively; Solving parameter values of an imaging model of an X-ray imaging device based on the double-circle feature and the straight line feature; the imaging model of the X-ray imaging device represents a transformation relationship between a world coordinate system and a screen coordinate system; Calculate the three-dimensional coordinate value of the point to be located in the world coordinate system based on the coordinate value of the point to be located in the space projected onto the anteroposterior X-ray image and the lateral X-ray image and the parameter value of the imaging model of the X-ray imaging device; The steps of constructing the imaging model of the X-ray imaging device include: Take any position in the X-ray imaging environment as the origin of the world coordinate system; The radiation source of the X-ray imaging device is used as the origin of the coordinate system of the X-ray imaging device; The two-dimensional projection of the object in the X-ray imaging environment through the X-ray imaging device and a certain plane is used as the image coordinate system, and the intersection of the optical axis and the image plane is used as the origin of the image coordinate system; Presenting the image information converted by the two-dimensional projection on a computer screen, and using the two-dimensional coordinate system on the screen as a screen coordinate system; Calculating the coordinate transformation relationship among the world coordinate system, the X-ray imaging device coordinate system, the image coordinate system, and the screen coordinate system to construct an imaging model of the X-ray imaging device; The origin of the X-ray imaging device coordinate system is taken as the optical center, and the Z axis of the X-ray imaging device coordinate system is made to coincide with the optical axis. The coordinate relationship between the point to be located in space in the world coordinate system and the X-ray imaging device coordinate system is calculated by the following formula: in, 、 、 is the translation component between the two coordinates, 、 、 is the rotation component between the two coordinate systems, 、 、 is the three-dimensional coordinate of the point to be located in space in the coordinate system of the X-ray imaging device, 、 、 It is the three-dimensional coordinate of the point to be located in the space in the world coordinate system; The X and Y axes of the X-ray imaging device coordinate system are made parallel to the horizontal and vertical axes of the image coordinate system, and the projection position coordinates of the point to be located in the space in the image coordinate system are calculated by the following formula: in, and are the horizontal and vertical coordinates of the projection position of the point to be located in the space in the image coordinate system, is the focal length of the X-ray imaging device; The coordinate value of the point to be located in the space in the screen coordinate system is calculated by the following formula: in, and It is the horizontal and vertical coordinate value of the point to be positioned in the space in the screen coordinate system. 、 It is the horizontal and vertical coordinate values of the origin of the image coordinate system in the screen coordinate system. is the actual horizontal axis size corresponding to the screen pixels, The actual vertical axis size corresponding to the screen pixels; Combining the above relationships, we get the transformation relationship from the world coordinate system to the screen coordinate system: According to the above transformation relationship from the world coordinate system to the screen coordinate system, the spatial line equation corresponding to a point in the image coordinate system is obtained: , ， ， ， ， ， ， ， ， ， ， in, , ; The mathematical expressions of the double-circle feature and the straight line feature in different coordinate systems are obtained as follows: The analytical equation of the space straight line in the coordinate system of the X-ray imaging device is obtained as: in, 、 、 、 It is the standard parameter of the spatial straight line equation in the coordinate system of the X-ray imaging device; The analytical equation for the projection of the spatial straight line in the X-ray imaging device coordinate system onto the image coordinate system is: in, 、 、 are the standard parameters of the analytical equation for the projection of the spatial straight line in the coordinate system of the above-mentioned X-ray imaging device onto the image coordinate system; The analytical equation of the circle in the X-ray imaging device coordinate system is obtained as: in, 、 、 are the standard parameters of the analytical equation of the circle in the X-ray imaging device coordinate system; The analytical equation for obtaining the projection of the circle in the X-ray imaging device coordinate system onto the image coordinate system is: in, The transformation function representing the projection of the horizontal coordinate of the X-ray imaging device coordinate system to the image coordinate system, The transformation function representing the projection of the ordinate of the X-ray imaging device coordinate system to the image coordinate system, 、 h 、 Standard parameters for the analytical equation of a circle projected from the X-ray imaging device coordinate system to the image coordinate system; The above equation is combined with the spatial straight line equation corresponding to a point on the image coordinate system to calculate the parameter value of the imaging model to .

2. The spatial positioning method of an X-ray image based on a navigation scale according to claim 1, characterized in that: According to the spatial straight line equation corresponding to a point on the image coordinate system, a spatial straight line corresponding to the coordinate value of the point to be located in space projected onto the anteroposterior X-ray image and the lateral X-ray image is calculated; The midpoint coordinates of the common perpendicular lines of the two spatial straight lines are used as the three-dimensional coordinates of the point to be located in the world coordinate system.

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