CN108742843A - A kind of C-arm space calibration device - Google Patents

Abstract

The present invention relates to medical domain more particularly to a kind of C-arm space calibration devices.The calibration device is made of 5 faces：Plane A and remaining intersect in 4 faces on one of them；Plane B, the plane C of two bandgap calibration points intersect with other 2 supporting planes respectively；Calibration point 1,2,5,6,7 is on plane C, and calibration point 3,4,8,9 is on plane B；(1,5,6) three point on a straight line；Straight line (1,5,6), (2,7), (3,8), (4,9) intersect at same point O2；Straight line (1,2), (3,4), (6,7), (8,9) intersect at point O1；Straight line (7,8), (6,9) intersect at a point O3；Straight line (1,4), (6,9) are parallel.Calibration point is using the material that can develop in X-ray line；Upper plane A, plane B, there is the mark that can be identified by vision tracking equipment on plane C, in computer-assisted surgery navigation system.The present invention can be placed on any one of C arm imaging spatial dimensions, especially at surgical site, provide C-arm space stated accuracy.

Description

A C-arm space calibration device

technical field

The invention relates to the medical field, in particular to a C-arm space scaler.

Background technique

In recent years, with the development of computer technology, computer-aided surgical navigation technology has been gradually applied to clinical practice. The most important problem in computer-aided surgical navigation technology is the registration of various spaces, especially CT, X-ray and other image spaces. The C-arm is a commonly used imaging device in surgical operations, and the X-rays taken by it are the registration data commonly used in the spatial registration of computer-aided surgical navigation technology. Therefore, many scholars have carried out a variety of studies on the spatial calibration of the C-arm, but the traditional C-arm calibration modules use parallel double-layer plane calibration devices for calibration, and the calibration devices are mostly placed on the image intensifier of the C-arm At one end, the surgical target is outside the space range of the calibrator. Due to the distortion of the X image of the C-arm, there are errors in the selection of calibration points. The traditional method is used to calibrate the internal and external parameters of the C-arm to calculate the spatial position of the surgical target and Inaccurate. Therefore, the present invention proposes a C-arm space calibration device that can be placed in the surgical target area to improve the spatial calibration accuracy of the surgical target.

Contents of the invention

(1) Technical problems to be solved

The object of the present invention is to provide a C-arm space calibration device, which is used for high accuracy of space calibration of surgical target points.

(2) Technical solution

In order to achieve the above object, a C-arm space calibration device of the present invention includes the following parts: it is composed of 5 surfaces; the upper plane intersects with the remaining 4 surfaces; the two planes with calibration points are respectively connected with the other 2 The support planes intersect.

According to the present invention, the calibration points 1, 2, 5, 6, 7 are on the plane, and the calibration points 3, 4, 8, 9 are on the plane B.

According to the present invention, the calibration point distribution satisfies the following characteristics:

(1,5,6) three points collinear;

Lines (1,5,6), (2,7), (3,8), (4,9) intersect at the same point O2;

Lines (1,2), (3,4), (6,7), (8,9) intersect at point O1;

Lines (7,8), (6,9) intersect at a point O3;

Lines (1,4) and (6,9) are parallel.

According to the present invention, the upper planes A, B and C have marks that can be recognized by a visual tracking device. The conversion relationship between the C-arm camera space and the visual space can be established by tracking the marks on the calibrator with the visual tracking device. Each visual tracking mark has 3 black and white corners, which are connected end to end along the direction of corner division, and there are two vertical vectors; the inner color of the corners is uniform, if it is white, the two vectors rotate counterclockwise, otherwise they rotate clockwise; The midpoint of the longer of the two straight lines is the origin of the coordinate system, the long axis is the X axis, and the short axis is the Y axis.

According to the present invention, the marking point adopts the material that can be developed under X-ray; the main body plane of the calibration device adopts the material that does not develop or micro-develops under X-ray.

According to the present invention, the internal and external parameters of the C-arm can be obtained by marking the positions of the marking points on the C-arm imaging. The model of the C-arm is as follows:

A ₁ x+A ₂ y+A ₃ z+A ₄ -A ₅ xu-A ₆ yu-A ₇ zu=u

A ₈ x+A ₉ y+A ₁₀ z+A ₁₁ -A ₅ xv-A ₆ yv-A ₇ zv＝v

Given the space coordinates (x _i , y _i , z _i ) (n=1, 2, Λ n) of n (n≥6) groups of marked points and the corresponding screen coordinates (u _i , v _i ) (n=1 , 2, Λ n), then 2n linear equations about A _i (i=1, 2, Λ 11) can be obtained, expressed as a matrix:

A _11×1 ＝[A ₁ A ₂ A ₃ A ₄ A ₅ A ₆ A ₇ A ₈ A ₉ A ₁₀ A ₁₁ ] ^T

C _(2×n)×1 ＝[u ₁ u ₂ … u _n v ₁ v ₂ … v _n ] ^T

so

E·A=C

A＝(E ^T E) ^-1 E ^T C

Thus A _i (i=1, 2, Λ 11) is obtained.

According to the present invention, the linear equation corresponding to the point in the image in space can be solved according to the calibrated camera parameters;

The spatial straight line l equation corresponding to a point on the image:

According to the present invention, each visual tracking mark has 3 black and white corners, which are connected end to end along the direction of corner division, and there are two vertical vectors; the inner color of the corners is uniform, if it is white, the two vectors rotate counterclockwise, otherwise Rotate clockwise; the midpoint of the longer of the two straight lines is the origin of the coordinate system, the long axis is the X axis, and the short axis is the Y axis.

(3) Beneficial effects

A C-arm space calibration device proposed by the present invention can be placed in the surgical target area to improve the spatial calibration accuracy of the surgical target.

Description of drawings

Fig. 1 is a schematic diagram of the positional relationship of the marking points of a C-arm space calibrator;

Fig. 2 is the plane distribution situation of marking point of the present invention;

Figure 3 is a schematic diagram of the position of the visual tracking sign;

Figure 4 is several examples of visual tracking markers;

Figure 5 is a schematic diagram of the use of the C-arm space calibration device;

Fig. 6 is an X-ray picture taken by the calibrator and the knee joint.

Detailed ways

A C-arm space marker according to the present invention will be described in detail below in conjunction with the embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the following embodiments.

Referring to Fig. 1, a C-arm space calibration device of the present invention includes the following parts: it is composed of 5 surfaces; the upper plane intersects with the remaining 4 surfaces; two planes with calibration points are respectively connected with other 2 supports The planes intersect. The calibration points are made of materials that can be developed under X-rays; the main plane of the calibration device is made of non-developed or micro-developed materials under X-rays.

Referring to Figure 2, the calibration points 1, 2, 5, 6, and 7 are on the plane, and the calibration points 3, 4, 8, and 9 are on the plane B.

With reference to Fig. 1, calibration point distribution satisfies the following characteristics:

1) (1,5,6) three points collinear;

2) The straight lines (1,5,6), (2,7), (3,8), (4,9) intersect at the same point O2;

3) Lines (1,2), (3,4), (6,7), (8,9) intersect at point O1;

4) The straight lines (7,8) and (6,9) intersect at a point O3;

5) The straight lines (1,4) and (6,9) are parallel.

Referring to FIG. 3 , there are signs on the upper plane A, plane B and plane C that can be recognized by the visual tracking device. The conversion relationship between the C-arm camera space and the visual space can be established by tracking the marks on the calibrator with the visual tracking device.

Figure 4 is a schematic diagram of several visual tracking signs. In addition to meeting the following requirements, visual tracking marking equipment can be designed by itself according to needs:

1) Each visual tracking mark has three black and white corners, which are connected end to end along the direction of corner division, and there are two vertical vectors;

2) The inner color of the corner point is uniform, if it is white, the two vectors rotate counterclockwise, otherwise they rotate clockwise;

3) The midpoint of the longer of the two straight lines is the origin of the coordinate system, the long axis is the X axis, and the short axis is the Y axis.

Referring to Figure 5, place the calibrator within the program range of the C-arm, while ensuring that the surgical target is within the space area of the calibrator, take X-rays, and record the position coordinates of the marker plate with the visual tracking device. According to the image coordinates of each marked point on the X-ray film as shown in Figure 6, the 11 internal and external parameters in the following C-arm model are solved.

The model of the C-arm is as follows:

A ₁ x+A ₂ y+A ₃ z+A ₄ -A ₅ xu-A ₆ yu-A ₇ zu=u

A ₈ x+A ₉ y+A ₁₀ z+A ₁₁ -A ₅ xv-A ₆ yv-A ₇ zv＝v

Given the space coordinates ( _xi , y _i , _zi ) (n=1, 2, Λ n) of n (n≥6) groups of marked points and the corresponding screen coordinates (u _i , v _i ) (n=1 , 2, Λ n), then 2n linear equations about A _i (i=1, 2, Λ 11) can be obtained, expressed as a matrix form:

A _11×1 ＝[A ₁ A ₂ A ₃ A ₄ A ₅ A ₆ A ₇ A ₈ A ₉ A ₁₀ A ₁₁ ] ^T

C _(2×n)×1 ＝[u ₁ u ₂ … u _n v ₁ v ₂ … v _n ] ^T

so

E·A=C

A＝(E ^T E) ^-1 E ^T C

Thus, A _i (i=1, 2, Λ 11) is obtained.

Conversely, according to the calibrated camera parameters, the linear equation corresponding to the point in the image in space can be solved;

The spatial straight line l equation corresponding to a point on the image:

According to the present invention, each visual tracking mark has 3 black and white corners, which are connected end to end along the direction of corner division, and there are two vertical vectors; the inner color of the corners is uniform, if it is white, the two vectors rotate counterclockwise, otherwise Rotate clockwise; the midpoint of the longer of the two straight lines is the origin of the coordinate system, the long axis is the X axis, and the short axis is the Y axis

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (8)

1. A C-shaped arm space calibrator is characterized by comprising the following parts:

is composed of 5 surfaces;

the upper plane is intersected with the other 4 planes;

the two planes B and C with the calibration points are respectively intersected with the other 2 supporting planes; wherein,

index points 1,2,5,6,7 are on plane C and index points 3,4,8,9 are on plane B;

(1,5,6) three points are collinear;

the straight lines (1,5,6), (2,7), (3,8), (4,9) intersect at the same point O2;

the lines (1,2), (3,4), (6,7), (8,9) intersect at a point O1;

the lines (7,8), (6,9) intersect at a point O3;

the straight lines (1,4), (6,9) are parallel.

2. A C-shaped arm space calibrator is characterized in that marks which can be recognized by visual tracking equipment are arranged on an upper plane A, a plane B and a plane C.

3. A C-shaped arm space calibrator is characterized in that a calibration point is made of a material which can be developed under X-rays; the plane of the main body of the calibrator is made of a non-developable or micro-developable material under X-ray.

4. A C-shaped arm space marker is characterized by being placed at any position of an imaging range of a C-shaped arm when in use.

5. A C-shaped arm space calibrator is characterized in that internal and external parameters of a C-shaped arm can be solved through the position of a marking point on an image of the C-shaped arm.

The model of the C-arm is as follows:

A₁x+A₂y+A₃z+A₄-A₅xu-A₆yu-A₇zu＝u

A₈x+A₉y+A₁₀z+A₁₁-A₅xv-A₆yv-A₇zv＝v

giving the space coordinate (x) of n (n ≧ 6) groups of mark points_i,y_i,z_i) (n-1, 2, L n) and corresponding screen coordinates (u)_i,v_i) (n-1, 2, L n), 2n of a can be obtained_i(i ═ 1,2, L11), expressed in the form of a matrix:

A_11×1＝[A₁A₂A₃A₄A₅A₆A₇A₈A₉A₁₀A₁₁]^T

C_(2×n)×1＝[u₁u₂… u_nv₁v₂… v_n]^T

therefore, it is not only easy to use

E·A＝C

A＝(E^TE)^-1E^TC

Thus obtaining A_i(i＝1,2,L 11)。

6. A C-shaped arm space calibrator is characterized in that a linear equation corresponding to a point in an image in space can be solved according to calibrated camera parameters;

the equation of a spatial straight line l corresponding to one point on the image:

7. a C-shaped arm space calibrator is characterized in that a conversion relation between a C-shaped arm camera space and a visual space can be established by tracking marks on the calibrator through visual tracking equipment.

8. A C-shaped arm space calibrator is characterized in that,

each visual tracking mark is provided with 3 black and white angular points which are connected end to end along the angular point segmentation direction, and two vertical vectors exist;

the inner side of the corner point has uniform color, if the color is white, the two vectors rotate anticlockwise, otherwise, the two vectors rotate clockwise;

the middle point of the longer straight line of the two straight lines is the origin of the coordinate system, the long axis is the X axis, and the short axis is the Y axis.