CN101561930B - Improved visualized method of virtual eversion of pipeline-shaped object - Google Patents

Abstract

The invention relates to a method in the technical field of image processing, in particular to an improved visual method of virtual eversion of a pipeline-shaped object. The method comprises the following steps: carrying out preprocessing and image segmentation to acquired three-dimensional image data of the pipeline-shaped object and obtaining the data of the inner wall and the outer wall of the pipeline-shaped object; based on the data of the outer wall, calculating and obtaining the central path of the outer wall; constructing a point charge model on the path; carrying out eversion to the data of the surface of the inner wall along the track of passing through electric field lines thereof to the outer side of the outer wall; and displaying the surface of the inner wall of a hollow cavity after eversion processing in a three-dimensional mode. The method carries out improvement by utilizing the central path of the smooth outer wall and avoids the problem of more serious structural deformation caused by eversion and the problem of structural overlapping.

Description

The visual method of virtual eversion of pipeline-shaped object of improvement

Technical field

What the present invention relates to is a kind of method of technical field of image processing, is specifically related to a kind of visual method of virtual eversion of pipeline-shaped object of improvement.

Background technology

Virtual endoscopic techniques is a kind of 3-D view visualization technique of observing pipeline-shaped object.This technological advantage is to need not brokenly ring or contact object itself, observes pipeline interior wall construction and state through Computer Image Processing simulation ground with the interior angle of spying on.But its visual angle is limited, can't observe the pipeline configuration simultaneously, can't judge the location of position in object of required concern on the inner-walls of duct intuitively.

Literature search through to prior art is found; People such as Zhao Jun are at disclosed " looking method outside the cavity property internal organs inwall virtual eversion formula three-dimensional " patent of invention (application number: proposed a kind of cavity property internal organs inwall visual method of virtual eversion 200610026664.0) on October 25th, 2006; And people such as Zhao Jun is at InternationalJournal of Biomedical Imaging (international biomedical imaging magazine; 2008 volumes, article numbering 763028) delivered Digital Eversion of a Hollow Structure:An Application in VirtualColonography (numeral of cavity structure is turned up and the application in a virtual coloscope) literary composition on.Above-mentioned technology has proposed a kind of method for visualizing of virtual eversion, has overcome virtual endoscope visual angle defect of insufficient.But the model that is based on the center path electric field has adopted the center path of inwall; When cavity inner wall unsmooth or for a long time protruding; The inwall center path also has a lot of complications, causes based on the electric field line distribution of inwall center path inhomogeneously thus, and direction and distance are inaccurate when causing structure and information on the object inwall to translate on the outer wall outward; The result of turning up who finally obtains is relatively poor, and malformation is more serious.

Summary of the invention

The present invention is directed to the deficiency of prior art, proposed a kind of visual method of virtual eversion of pipeline-shaped object of improvement.The present invention utilizes the center path of smooth outer wall to improve, the more serious malformation problem that can bring after avoiding turning up with avoided the structure overlap problem.

The present invention realizes through following technical scheme:

The present invention is the pipeline-shaped object 3 d image data to obtaining at first, is optimized pre-service and image segmentation, obtains the inner wall surface and the outer wall surface of pipeline-shaped object; Use center path generating algorithm to obtain the outer wall center path then; Then on the outer wall center path, make up point charge model and calculate the electric field line that exhales from these point charges; Subsequently the data of the inner wall surface track along electric field line is turned up to outer exterior wall; The pipeline-shaped object inner wall surface that to turn up at last after handling shows with three-dimensional picture, supplies the user from the outside visual angle of pipeline the inwall after turning up to be observed.

The present invention includes following steps:

(1) the pipeline-shaped object 3 d image data (with means such as CT, industry CT, MRI, ultrasonic imagings) to obtaining adopts suitable method to be optimized pre-service and image segmentation, obtains the inner and outer wall of pipeline-shaped object.Said appropriate pretreatment is meant with the method for cutting apart, according to the difference of three-dimensional data imaging technique, chooses corresponding supporting image optimization pre-service and dividing method to obtain complete inner and outer wall data.Optimization preprocess method commonly used has filtering and noise reduction, contrast adjustment, interpolation etc.Image partition method commonly used has region growing, Level Set Method etc.

(2) based on the outer wall surface data computation and obtain the outer wall center path.Described center path is meant: at an inner middle track shaft of pipeline-shaped object, each point all satisfies optimum central point decision criteria on the track.And center path generating algorithm just is meant the method that calculates center path according to decision criteria.Center path generating algorithm has topology refinement method, range conversion method, Level Set Method, manual standardization etc.

(3) on the outer wall center path, make up point charge model.Described point charge model is meant: in order to calculate the electric field line track, and emulation distributed points electric charge on center path, and other data areas do not have the quantity of electric charge in the pipeline-shaped object.From each point charge calculating electric field line.Described electric field line is meant: under the basic electromagnetic field theory, and the electric field line in the electric field that a plurality of point charges interactions produce.Whole center path point charge One's name is legion in the practical application can in conjunction with near the interaction of several point charges of regional area it, calculate the electric field line of all directions from each point charge on the center path.Electric field line will pass the inner wall surface of pipeline-shaped object and the outer wall that Gong to turn up, the part that exceeds outer wall be no less than this electric field line from the inner wall surface to the outer wall the distance of process.

(4) data of inner wall surface are turned up to outer exterior wall along the track that passes its electric field line.Be about to each point in the cavity inner wall surface data that obtains that extracts, be mapped to the opposite side of outer wall along the track that passes its electric field line, and draw out the surface data after turning up again.The distance that is mapped to outer wall can be the distance of inner wall surface along electric field line to outer wall, also can be that the distance of inner wall surface along electric field line to outer wall multiply by the value that a coefficient obtains, so that in concrete the application, improve effect of visualization.

(5) the cavity inner wall surface that will turn up after handling shows with three dimensional form.Promptly, carry out three-dimensional visualization and show the inner wall surface after turning up.Observation visual angle is positioned at the pipeline outside, and can be chosen arbitrarily by the user.

The present invention's pipeline-shaped object that outer wall is smooth for inwall is rough; Beneficial effect with respect to original virtual everting method based on inwall center path electric field line is: 1, avoid more convexity being arranged and causing the inwall center path tortuous when big, the more serious malformation problem that can bring after turning up when inwall.2, make the convexity on the inwall after turning up, can keep good direction, the structure of avoiding having is overlapping.

Description of drawings

Fig. 1: the distribution schematic diagram of center path and electric field line in the pipeline-shaped object.

Embodiment

Below in conjunction with accompanying drawing embodiments of the invention are elaborated: present embodiment provided detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment being to implement under the prerequisite with technical scheme of the present invention.

Embodiment

1. there is the industry CT faultage image data of fluctuating industrial pipeline (use year for a long time, corrosion and deposition are arranged) to carry out Filtering Processing to obtaining an outer wall smooth inner wall, comprises gaussian filtering and medium filtering, remove denoising.Use the 3D region growth algorithm from faultage image, to be partitioned into rough pipeline-shaped object internal cavities.Re-use three-dimensional level set partitioning algorithm, segmentation result as initial value, as velocity image, further is partitioned into accurate interior of articles cavity surface with former faultage image.The service orientation gradient method extracts the surfaces externally and internally profile of pipeline-shaped object from former faultage image, this profile is as velocity image, and the segmentation result of interior of articles cavity reuses the outer wall surface that three-dimensional level set partitioning algorithm extracts object as initial value.

2. service range transfer pair object outer wall surface is obtained the minor increment that this puts outer wall surface with interior every bit.Adopt the Dijkstra critical path method (CPM) to generate center path: starting point and the terminal point of promptly in cavity, choosing center path; Then with every bit in the cavity to the inverse of the distance value of outer wall surface as weights; Carry out Shortest Path Searching, get all weights minimum some connection source and terminal point and obtain the outer wall center path.The outer wall center path is more level and smooth than inwall center path, does not have too much complications, better the whole shape of reacting pipe.

3. the point charge of a unit of the virtual distribution of every bit on the outer wall center path; The direction of trying to achieve near concentricity path partial vertical this point charge through each point charge is decided to be inceptive direction; Calculate this point charge under point charge effect around it according to basic Theory of Electromagnetic Field; To the electric field line track that inceptive direction sends, obtain the bent cross section of forming by electric field line.For example ought calculate certain 1 P on the center path ₀The time, get point charge generation electric field in its K neighborhood, consider that front and back are total to 2K+1 point charge on the center path:

P _-K，P _-(K-1)，L，P ₀，L，P _(K-1)，P _K。These points are equally distributed on center path.Need obtain under above 2k+1 point charge interacts, from P ₀The cross section that the electric field line that sets out constitutes.

If ρ is the step-length when drawing electric field line.Value obtains more little accurate more, consuming timely also can increase but calculate thereupon, and ρ desirable 0.1 in the instance.If n is for putting the electric field number of lines of required sampling on the center path each, n desirable 400 in the instance.

At first, demand is appeared P ₀Point, and logical center path is at P ₀The plane of the partial vertical of point.

This plane can be represented by a French.Point is P ₀Point, normal vector Can be by P ₁-P _-1, and through the normalization acquisition.Can make

Coordinate be (n ₁, n ₂, n ₃), P ₀Coordinate be (p ₁, p ₂, p ₃).So this plane can be expressed as: n ₁(x-p ₁)+n ₂(y-p ₂)+n ₃(z-p ₃)=0.

And regulation

is the positive dirction in the plane.Can make

by obtaining after the following formula computing:

must be arranged at this moment, also is that

is vertical with

.Again carried out normalization and handle, can obtain positive dirction in the plane after the normalization

So, get P ₀Be true origin, the positive dirction in the plane Be y direction of principal axis, normal vector

Be the z direction of principal axis,

Be the x direction of principal axis, the coordinate system that definable is new.In new coordinate system, the coordinate of the vector of unit length of each change in coordinate axis direction in former coordinate system is following:

${\stackrel{V}{e}}_x=\left(\begin{array}{c}{l}_2{n}_3-l_3{n}_2\\ l_3{n}_1-l_1{n}_3\\ l_1{n}_2-l_3{n}_1\end{array}\right),{\stackrel{V}{e}}_y=\left(\begin{array}{c}{l}_1\\ l_2\\ l_3\end{array}\right),{\stackrel{V}{e}}_z=\left(\begin{array}{c}{n}_1\\ n_2\\ n_3\end{array}\right).---\left(3\right)$

In new coordinate system, the location of the initial position of electric field line is fairly simple, all is positioned at the x-y plane, can be by the polar coordinates in the plane (ρ, θ _i) represent.Wherein, ρ is step parameter, θ _iCan try to achieve through following formula by parameter n:

${\mathrm{\θ}}_i=\frac{2\mathrm{\π}\×i}{n},$ i＝0，1，2.L，n-1.(4)

So the coordinate of the electric field line initial position in new coordinate system is following:

$\left(\begin{array}{c}{x}_i^{\′}\\ y_i^{\′}\\ z_i^{\′}\end{array}\right)=\left(\begin{array}{c}\mathrm{\ρ}\cos {\mathrm{\θ}}_i\\ \mathrm{\ρ}{\sin \mathrm{\θ}}_i\\ 0\end{array}\right),$ i＝0，1，2，L，n-1.(5)

Will be in new coordinate system the initial position of electric field line, be converted in the original coordinate system, can adopt following formula to realize:

$\left(\begin{array}{c}{x}_i\\ y_i\\ z_i\end{array}\right)=\left(\begin{array}{ccc}{\stackrel{V}{e}}_x& {\stackrel{V}{e}}_y& {\stackrel{V}{e}}_z\end{array}\right)\left(\begin{array}{c}{x}_i^{\′}\\ y_i^{\′}\\ z_i^{\′}\end{array}\right)+\left(\begin{array}{c}{p}_1\\ p_2\\ p_3\end{array}\right),$ i＝0，1，2，L，n-1(6)

For current location is Q (q ₁, q ₂, q ₃), needing to calculate institute has a P _-n, P _-(n-1), L, P ₀, L, P _(n-1), P _nWhen supposing all to have the unit positive charge, the electric field intensity direction of ordering for Q.Utilize the superposition principle of electric field force, can calculate each P _iElectric field intensity direction to Q is ordered adds up again.

The electric field intensity formula that a bit produced of each point charge in the space is following:

Wherein,

is the vector of point charge to this point, i.e.

Because each point charge is to the electric field intensity of this point; value is identical, so can omit.So, calculate the electric field intensity direction and can adopt following formula to carry out:

Then; After again

being carried out the normalization processing; Can obtain the direction of electric field line, also promptly have

Can try to achieve the point coordinate Q ' after the ρ distance of advancing on the electric field line direction according to current location Q and current normalization direction of an electric field

.Also promptly:

Point if advance after the ρ distance still is between inner-walls of duct and the outer wall, then double counting electric field line direction, and the distance of the ρ that advances, the outer wall surface that has arrived or crossed pipeline up to resulting point.In like manner accomplish P ₀The electric field line of all directions calculates on the point.As long as it is enough close that electric field line is obtained, then the point on electric field line can be regarded the cross section of being taken out as.

4. the every bit on the inner-walls of duct surface that is obtained is mapped to the opposite side on pipeline outer wall surface along electric field line.Detailed process is: become to make C _iFor by the resulting bent cross section of the point on i the center path, F _IjBe cross section C _iOn j bar electric field line.Definition M is the inside surface of internal organs, and R is an outer wall, and E is for turning up back resulting.Defining point m again _IjBe F _IjWith the intersection point of M, r _IjBe F _IjWith the intersection point of R, e _IjBe F _IjIntersection point with E.The process of turning up along the electric field line numeral is just by each m _IjAnd r _IjAgain along F _IjObtain e _Ij, again by all e _IjConstitute the surperficial E after turning up.In order to try to achieve e _Ij, the following principle of definable: from a m _IjTo a r _IjAt F _IjOn segment of curve length with the some r _IjTo an e _IjAt F _IjOn the segment of curve equal in length.Repeat so the just complete virtual extraterrestrial outside of translating into outer wall, the surface of inwall.Owing to used more level and smooth outer wall center path, the information on the surface of inwall is able to turn up to outer exterior wall more truly.

5. the inner-walls of duct surface data that uses three-dimensional visualization kit such as VTK will be mapped to outside the outer wall repaints, and shows with user's controllable mode.The user can change the visual angle arbitrarily, and this surface is observed from the pipeline outside.

Such embodiment has kept each item advantage based on inwall center path virtual eversion technology, can show in that outside surface is virtual like the inwall of pipeline, and the user can change different visual angles neatly; Both can be observed the configuration of pipeline, and can analyze structure trickle on the inwall again, and interesting areas is accurately located.Avoided the more serious malformation problem that produces based on inwall center path virtual everting method simultaneously, for the damage of observing with the analysis conduit inwall provides more reliable data.

After present embodiment was applied to the virtual eversion of the rough and pipeline-shaped object that outer wall is smooth of inwall, effect was better than the method based on the inwall center path, can be applicable to the virtual eversion of various pipeline-shaped objects.As shown in Figure 1, when inner-walls of duct have more when protruding, will be tortuous thereupon based on the center path of inwall, according to original method hereinto wit directly go up distributed charge and will cause electric field line distribution inhomogeneous, and then the malformation after causing turning up.Center path must have good center degree, and is enough level and smooth again, avoids sharp turn and corner angle.The center path of smooth outer wall is more more smooth than the center path of uneven inwall, and distributed charge can obtain uniform and stable electric field line on the outer wall center path.Turn up along outer wall center path electric field line, both can keep each item advantage of original virtual everting method, can avoid more convexity being arranged and the inwall center path is tortuous when big, the serious malformation problem that can bring after turning up again when inwall.Therefore turn up along outer wall center path electric field line and help the nondestructive examination of inner-walls of duct.

Claims (9)

1. the visual method of virtual eversion of pipeline-shaped object of an improvement is characterized in that, may further comprise the steps:

(1) the pipeline-shaped object 3 d image data to obtaining carries out pre-service and image segmentation, obtains the data of the inner and outer wall of pipeline-shaped object;

(2), calculate and obtain the outer wall center path based on the outer wall data;

(3) on the outer wall center path, make up point charge model;

(4) data of inner wall surface are turned up to outer exterior wall along the track that passes its electric field line;

(5) the cavity inner wall surface that will turn up after handling shows with three dimensional form.

2. the visual method of virtual eversion of pipeline-shaped object of improvement according to claim 1 is characterized in that, described pretreated method comprises filtering and noise reduction, contrast adjustment or interpolation method.

3. the visual method of virtual eversion of pipeline-shaped object of improvement according to claim 1 is characterized in that, the method for described image segmentation comprises region growing or Level Set Method.

4. the visual method of virtual eversion of pipeline-shaped object of improvement according to claim 1; It is characterized in that; The data of described inner and outer wall are meant: according to the three-dimensional data imaging technique, choose supporting image optimization pre-service and dividing method to obtain complete inner and outer wall data.

5. the visual method of virtual eversion of pipeline-shaped object of improvement according to claim 1 is characterized in that, described center path is meant: at an inner middle track shaft of pipeline-shaped object, each point all satisfies optimum central point decision criteria on the track.

6. the visual method of virtual eversion of pipeline-shaped object of improvement according to claim 1; It is characterized in that; Described center path; Its generating algorithm is the method that calculates center path according to decision criteria, comprises topology refinement method, range conversion method, Level Set Method or manual standardization.

7. the visual method of virtual eversion of pipeline-shaped object of improvement according to claim 1; It is characterized in that; Described point charge model is meant: in order to calculate the electric field line track, emulation distributed points electric charge on center path; And other data areas do not have the quantity of electric charge in the pipeline-shaped object, from each point charge calculating electric field line.

8. the visual method of virtual eversion of pipeline-shaped object of improvement according to claim 1; It is characterized in that; Described track turns up; Be with extract each point in the cavity inner wall surface data that obtains, be mapped to the opposite side of outer wall, and draw out the surface data after turning up again along the track that passes its electric field line.

9. the visual method of virtual eversion of pipeline-shaped object of improvement according to claim 8; It is characterized in that; The described distance that is mapped to outer wall is the distance of inner wall surface along electric field line to outer wall, or the distance of inner wall surface along electric field line to outer wall multiply by the value that a coefficient obtains.

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