CN100558302C - A kind of sphere center locating method based on the imaging of 3D sequence high accuracy - Google Patents

Abstract

The present invention relates to a kind of sphere center locating method based on the imaging of 3D sequence high accuracy, it may further comprise the steps: (1) supposes at first on the sectional view that the area S and the cross section of circle satisfy normal distribution between the coordinate figure on the scanning direction; (2) along the cross section circular image of ball at same axial arbitrary scan three width of cloth diverse locations, or scanning obtain the cross section circular image of two width of cloth diverse locations after, simulate the 3rd width of cloth cross section circular image, form a class value at the coordinate figure of scanning direction by this cross section area of a circle and this cross section circle; Three class values that (3) will obtain simulate a Gaussian curve, and the coordinate figure of area maximum point correspondence is the coordinate figure of the centre of sphere on this scanning direction on the curve; (4) after the same method, obtain the coordinate figure of the centre of sphere,, combine and be sphere centre coordinate each axial coordinate value at two other change in coordinate axis direction.The present invention has improved the precision that the centre of sphere calculates greatly, makes the demarcation of demarcation mould in the nuclear magnetic resonance surgery systems more accurate.

Description

A kind of sphere center locating method based on the imaging of 3D sequence high accuracy

Technical field

The present invention relates to sphere center locating method, particularly about a kind of sphere center locating method that in interventional therapy, adopts fixing imaging device to obtain based on the imaging of 3D sequence high accuracy.

Background technology

Interventional therapy is to use a kind of invasive treatment that modern high tech method carries out, and it is under the guiding of medical imaging device, and accurate operating theater instruments such as special conduit, seal wire is introduced human body, and internal lesions is diagnosed and topical therapeutic.Most projects of interventional therapy are all carried out in blood vessel, it need not be operated on, only need one less than the big little openning of the grain of rice, tubule insert can treat in the blood vessel manyly can't treat in the past, must operative treatment or the not good enough disease of medical treatment curative effect, as coronary heart disease, arrhythmia, tumor, hemangioma, various hemorrhage, cerebrovascular malformation etc.Interventional therapy have do not operate on, wound is little, recovery is fast, good effectiveness.In traditional intervene operation, the doctor relies on the perusal lesion image, by rule of thumb operating theater instruments is placed into the target location, and the error between operation device that this mode causes and the lesions position location can influence the quality of operation.

The applicant provides a kind of doctor of the making focus that the while can be seen on screen and the interventional navigation system of operating theater instruments relative position for this reason, in this system, need be provided with one and be used for focus and operating theater instruments place coordinate system are demarcated, demarcate mould the image in the different coordinates is introduced the solid of observing in the same coordinate system.Yet because the characteristic point of demarcating on the mould is not a point, but bead with certain volume, therefore when using that fixedly imaging device scans the characteristic point on the demarcation mould, being positioned at the characteristic point that is fixed into as the device scan center is different with the resulting figure of the characteristic point on being positioned at the edge, promptly can not from scanning patter, once obtain the center of characteristic point, the range sweep center is far away more, and anamorphose is big more, and the image that obtains characteristic point is got over distortion.

Summary of the invention

At the problems referred to above, the purpose of this invention is to provide a kind ofly in being fixed into picture equipment drawing picture, can accurately calculate the sphere center locating method of demarcating characteristic point sphere center position in the mould based on the imaging of 3D sequence high accuracy.

For achieving the above object, the present invention takes following technical scheme: a kind of sphere center locating method based on the imaging of 3D sequence high accuracy, and it may further comprise the steps: (1) supposes at first on the sectional view that the area S and the cross section of circle satisfy normal distribution between the coordinate figure on the scanning direction; (2) along the cross section circular image of ball at same axial arbitrary scan three width of cloth diverse locations, or scanning obtain the cross section circular image of two width of cloth diverse locations after, simulate the 3rd width of cloth cross section circular image, form a class value at the coordinate figure of scanning direction by this cross section area of a circle and this cross section circle; Three class values that (3) will obtain simulate a Gaussian curve, and the coordinate figure of area maximum point correspondence is the coordinate figure of the centre of sphere on this scanning direction on the curve; (4) after the same method, obtain the coordinate figure of the centre of sphere,, combine and be sphere centre coordinate each axial coordinate value at two other change in coordinate axis direction.

Wherein in the step (2), the described cross section area of a circle and this circle comprise that in the class value that the coordinate figure of scanning direction is formed (x, y z) represent sphere centre coordinate to usefulness, and d represents the distance of the centre of sphere to the cross section circle, R ₀Represent the radius of a ball, r represents the cross section radius of circle, and (a, b c) represent the round heart in cross section, and t1 represents cross section circule method line direction; There is following geometrical relationship in they:

d ²+r ²＝R ₀ ² (1)

The approximate radius R of known spheroid ₀,, can obtain central coordinate of circle (a, the b of cross section circle by analysis image, c), the area S of circle, utilize area of a circle S can obtain cross section radius of circle r, utilize that the centre of sphere and central coordinate of circle can obtain that the centre of sphere justifies to the cross section apart from d, thereby utilize formula (1) obtain this sphere centre coordinate on axially (x, y, z).

By geometrical relationship, as long as know the wherein parameter of two faces, the method for available geometry is listed following simultaneous equations, solves the coordinate figure of the centre of sphere:

To first face:

$\left\{\begin{array}{c}{(x-a_1)}^2+{(y-b_1)}^2+{(z-c_1)}^2+\frac{S_1}{\mathrm{\π}}={R_0}^2\\ \frac{x-a_1}{{t1}_x}=\frac{y-b_1}{{t1}_y}=\frac{z-c_1}{{t1}_z}\end{array}\right.---\left(2\right)$

Can solve two class values lays respectively at about the centre of sphere;

To second face:

$\left\{\begin{array}{c}{(x-a_2)}^2+{(y-b_2)}^2+{(z-c_2)}^2+\frac{S_2}{\mathrm{\π}}={R_0}^2\\ \frac{x-a_2}{{t2}_x}=\frac{y-b_2}{{t2}_y}=\frac{z-c_2}{{t2}_z}\end{array}\right.---\left(3\right)$

Can solve two class values lays respectively at about the centre of sphere;

By four centre ofs sphere that solve above, with wherein nearest 2 average, be the coordinate figure of the centre of sphere at this.

Adopt technique scheme, the present invention has the following advantages: the present invention is by calculating the sphere centre coordinate of spheroid on each axial scanning direction of 3D, utilize the gaussian curve approximation algorithm to determine sphere centre coordinate, the characteristics of nuclear magnetic resonance had both been fully taken into account, overcome the deviation that existing algorithm is caused by the magnetic resonance image (MRI) distortion again, improved the precision that the centre of sphere calculates greatly, made the demarcation of demarcation mould in the nuclear magnetic resonance surgery systems more accurate.

Description of drawings

Fig. 1 demarcates the mode structure sketch map

Fig. 2 demarcates modular character layer structural representation

Fig. 3 adopts fixedly that imaging device becomes the image sketch map

Fig. 4 is the sketch map of three sectional positions of Fig. 3

Fig. 5 is the sketch map that spheroid is arranged in three-dimensional coordinate

Fig. 6 is the Gaussian curve that simulates along the scanning of the z axle in the three-dimensional coordinate

Fig. 7 is the geometrical relationship sketch map of the embodiment of the invention

The specific embodiment

Below in conjunction with drawings and Examples the present invention is described in detail.

At first lift one and demarcate mould example (demarcating mode structure does not limit therewith), the problem to be solved in the present invention is done one simply to be introduced, as shown in Figure 1 and Figure 2, the demarcation mould of this case introduction is a rectangle demarcation mould body 1 of being made 300mm * 240mm * 200mm by pmma material, it is similar to demarcate mould body 1 other five faces except that the bottom surface, each face all has certain thickness characteristic layer 2, adopts bonding between each face or alternate manner is tightly connected.All be arranged at intervals with the spheroid of one deck in each characteristic layer 2 inside as characteristic point 3, five faces all characteristic points 3 formed feature point set I jointly.Outer surface at each characteristic layer 2 is corresponding with the position of each characteristic point 3, and a pit as characteristic point 4 is set, and the characteristic point 4 on five outer surfaces has been formed feature point set II jointly.Demarcating mould body 1 inside, is to demarcate mould solution 5 in the space that six bread gets up promptly, and this class is demarcated mould solution 5 can adopt sodium chloride solution, copper-bath etc., has the effect that improves load and signal to noise ratio.

Demarcate mould and mainly be and be used to demarcate and check mutual alignment between each coordinate system, because the characteristic point 3 of feature point set I can be analyzed from the image that MR imaging apparatus became and obtain, the characteristic point 4 of feature point set II can measure in tracked system identification, and the relation between feature point set I and the feature point set II known (being called the geological information of demarcating mould), as long as know the coordinate of characteristic point 3 (perhaps characteristic point 4 among the feature point set II) among the feature point set I wherein, just can extrapolate the coordinate of characteristic point 4 among the feature point set II (or among the feature point set I characteristic point 3), just can be created as transformation relation between picture device coordinate system and the tracking system coordinate system by the relation between them.

Yet, according to various imaging device (MR imaging apparatus, ct apparatus (CT), C type arm X line equipment etc.) imaging characteristics as can be known, when fixedly imaging device scans the characteristic point 3 among the feature point set I in the demarcation mould (as shown in Figure 3), because characteristic point 3 is not a point, but spheroid, scanning gained image is that integration obtains, and resulting image is also irregular, position particularly far away more apart from the device scan center, the anamorphose that obtains is big more (as a among Fig. 4, b, shown in the c), therefore can not from image, directly obtain the centre of sphere of spheroid.

As Fig. 5, shown in Figure 6, in order to obtain the characteristic point 3 real centre ofs sphere, the present invention supposes that at first the area S and the cross section of circle on the sectional view satisfy normal distribution between the coordinate figure on the scanning direction; With being fixed into picture device scan characteristic point 3, and the cross section circular image of arbitrary scan three width of cloth diverse locations along the same axis, a certain cross section area of a circle S on the scanning direction and can form a class value at the coordinate figure of scanning direction with this cross section; By geometry as can be known, as long as obtain three groups of such values, just can simulate a Gaussian curve, the coordinate figure that area maximum point (peak point) is corresponding on the curve is exactly the coordinate figure of the centre of sphere on this scanning direction.Curve 0 on the z axle reaches peak value, illustrates that this point is exactly that the centre of sphere is at the axial coordinate figure of z.After the same method, can obtain the coordinate figure of the centre of sphere, utilize on axially three cross sections to calculate the centre of sphere each, combine and to determine sphere centre coordinate at this coordinate figure on axially in two other coordinate axes (x, y) direction.

In scanning process, may have to two width of cloth sectional views sometimes, at this moment at first need simulate the 3rd width of cloth sectional view, and then calculate the coordinate position of the centre of sphere with said method by this two width of cloth figure through the center of circle.

Describe below by instantiation.

As shown in Figure 7, go to cut a spheroid with a plane, can obtain a circle, (x, y z) represent sphere centre coordinate, and d represents the distance of the centre of sphere to the cross section circle, R among the figure ₀Represent the radius of a ball, r represents the cross section radius of circle, and (a, b c) represent the round heart in cross section, and t1 represents cross section circule method line direction.There is such geometrical relationship between them:

d ²+r ²＝R ₀ ² (1)

The approximate radius of known cod-liver oil bead is 3mm, by the analysis of magnetic resonance image, can obtain the central coordinate of circle (a of cross section circle, b, c), the circle area S, utilize area of a circle S can obtain cross section radius of circle r, utilize the centre of sphere and central coordinate of circle can obtain d, thereby can utilize formula (1) obtain this sphere centre coordinate on axially (x, y, z).

By geometrical relationship, we know, as long as known the parameter of two faces, just can list following simultaneous equations with how much method, and the coordinate figure that solves the centre of sphere comes:

To first face:

$\left\{\begin{array}{c}{(x-a_1)}^2+{(y-b_1)}^2+{(z-c_1)}^2+\frac{S_1}{\mathrm{\π}}={R_0}^2\\ \frac{x-a_1}{{t1}_x}=\frac{y-b_1}{{t1}_y}=\frac{z-c_1}{{t1}_z}\end{array}\right.$

Can solve two class values like this, be each one up and down from how much.

To second face:

$\left\{\begin{array}{c}{(x-a_2)}^2+{(y-b_2)}^2+{(z-c_2)}^2+\frac{{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="C20071006490100092.png"\; state="\{\{state\}\}">S</figure-callout>}}_2}{\mathrm{\&pi;}}={R_0}^2\\ \frac{x-a_2}{{t2}_x}=\frac{y-b_2}{{t2}_y}=\frac{z-c_2}{{t2}_z}\end{array}\right.$

Also can solve two class values, also be each one up and down.

By four centre ofs sphere that solve above, should there be two to be same point (having error certainly certainly) in fact

So we ask the distance of every point-to-point transmission, l ₁, l ₂, l ₃, l ₄, then minimum 2 of distance should be exactly correct centre of sphere point, so be averaged, obtain the initial value of the centre of sphere that we want at these 2.

The initial value that the centre of sphere has been arranged is also known radius of a ball R ₀(R ₀Greatly about about 3mm), also just obtained crossing the cross section circle information of the centre of sphere, comprehensive existing two cross sections circle information just can be utilized the inventive method calculating centre of sphere.Because the information (center of circle of three cross section circles has been arranged, radius), can calculate the area of a circle, because the central coordinate of circle value is known, also just obtained 3 class values, every class value is formed at the coordinate figure of scanning direction by a certain cross section area of a circle on the scanning direction with this cross section, this three class value as the point coordinates on the Gaussian curve, just can simulate a Gaussian curve, thereby obtain the coordinate figure of the centre of sphere on this scanning direction.Profit uses the same method, and can obtain the coordinate figure of the centre of sphere on other both direction, thereby obtains the sphere center position coordinate.

Claims (2)

1, a kind of sphere center locating method based on the imaging of 3D sequence high accuracy, it may further comprise the steps:

(1) normal distribution is satisfied in area S and the cross section of at first supposing circle on the sectional view between the coordinate figure on the scanning direction;

(2) along the cross section circular image of ball at same axial arbitrary scan three width of cloth diverse locations, or scanning obtain the cross section circular image of two width of cloth diverse locations after, simulate the 3rd width of cloth cross section circular image, form a class value at the coordinate figure of scanning direction by each cross section area of a circle and this cross section circle through the center of circle;

Three class values that (3) will obtain simulate a Gaussian curve, and the coordinate figure of area maximum point correspondence is the coordinate figure of the centre of sphere on this scanning direction on the curve;

(4) after the same method, obtain the coordinate figure of the centre of sphere,, combine and be sphere centre coordinate each axial coordinate value at two other change in coordinate axis direction.

2, a kind of sphere center locating method as claimed in claim 1 based on the imaging of 3D sequence high accuracy, it is characterized in that: wherein in the step (2), the described cross section area of a circle and this circle comprise usefulness (x in the class value that the coordinate figure of scanning direction is formed, y, z) represent sphere centre coordinate, d represents the distance of the centre of sphere to the cross section circle, R ₀Represent the radius of a ball, r represents the cross section radius of circle, and (a, b c) represent the round heart in cross section, and t1 represents cross section circule method line direction; There is following geometrical relationship in they:

d ²+r ²＝R ₀ ² (1)

The approximate radius R of known spheroid ₀,, obtain central coordinate of circle (a, the b of cross section circle by analysis image, c), the area S of circle, utilize area of a circle S to obtain cross section radius of circle r, utilize that the centre of sphere and central coordinate of circle obtain that the centre of sphere justifies to the cross section apart from d, thereby utilize formula (1) obtain this sphere centre coordinate on axially (x, y, z).

By geometrical relationship, as long as know the wherein parameter of two faces, list following simultaneous equations with how much method, solve the coordinate figure of the centre of sphere:

To first face:

$\left\{\begin{array}{c}{(x-a_1)}^2+{(y-b_1)}^2+{(z-c_1)}^2+\frac{S_1}{\mathrm{\&pi;}}={R_0}^2\\ \frac{x-a_1}{{t1}_x}=\frac{y-b_1}{{t1}_y}=\frac{z-c_1}{{t1}_z}\end{array}\right.---\left(2\right)$

Solve two class values;

To second face:

$\left\{\begin{array}{c}{(x-a_2)}^2+{(y-b_2)}^2+{(z-c_2)}^2+\frac{S_2}{\mathrm{\&pi;}}={R_0}^2\\ \frac{x-a_2}{{t2}_x}=\frac{y-b_2}{{t2}_y}=\frac{z-c_2}{{t2}_z}\end{array}\right.---\left(3\right)$

Solve two class values;

By four centre ofs sphere that solve above, with wherein nearest 2 average, be the coordinate figure of the centre of sphere at this.

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