CN101006469A - System and method for creating a panoramic view of a volumetric image - Google Patents

Abstract

A system and method for creating a panoramic projection of a volumetric image of an object is disclosed. A virtual camera is placed in a center of a cubic space within the object. Images obtained from the camera are projected onto a single plane. A front image is mapped in a window at a center of the plane. A left, right, top and bottom image of the cubic space are mapped around the rectangular window such that the left, right, top and bottom images form a continuous image surrounding the rectangular window.

Description

Be used to produce the system and method for the panoramic view of volumetric image

The cross reference of related application

It is the interests of 60/561,183 U.S. Provisional Patent Application that the application requires in the application number that on April 9th, 2004 submitted to, by reference with the whole combinations of its content.

Technical field

The present invention is intended to a kind of system and method that is used to produce the panoramic view of volumetric image, more specifically, relates to the system and method that a kind of three-dimensional panorama that is used to produce the volumetric image of object (for example colon) shows.

Background technology

The virtual endoscopy method is a kind of noninvasive diagnostic routine of inside surface of the anatomical structure that is intended to detect inside of human body.Use advanced image processing techniques, three-dimensional (3D) model is able to reconstruct from a series of high-resolution two dimensions (2D) image.Thereby the doctor can manually or utilize the self-navigation algorithm to navigate in the 3D dummy model.

To one of use of the tool future of virtual endoscopy method is colorectal cancer patient's examination (screening).The traditional colonoscopy of virtual endoscopy method simulation also has following additional advantage, promptly lower invasion and have more attractive forces potentially as a kind of screening method.The extra benefit of the relative conventional junction enteroscopy of virtual coloscope inspection is the ability of passing through colon on the direction of advancing and falling back.Although this two-way navigation has significantly increased the amount on shown surface, the essential part of colon still is blocked on after the haustrum fold.

Many technology have been suggested some circumscribed image projection that overcome standard 3D visualization technique in order to generation.Thereby these technology are sought to show more colon surface and are increased polyp and check sensitivity.Some views generate by placing virtual camera and project image onto on the corresponding metope at the center of observation space.

A kind of known technology is used the cube observation space, wherein camera be positioned at cubical center and on each face with the viewing angle projected images of 90 degree.This cube then is launched into the single plane of 360 degree visual fields of an expression colon surface.An example of this projection is shown in Figure 1.In order to reduce the interference that the uncontinuity that produces with this representation causes, little image is added as the tablet that is adjacent to each face.Off-line animated image sequence is from originally generating along the selected a plurality of point samples of center path that pass colon.Fig. 1 shows a single frame that uses the animation sequence of this cube mapping.Each square shown in Fig. 1 is all represented cubical different side.As shown, the side is marked as a left side 102, bottom 104, front portion 106, top 108, the right side 110 and rear portion 112.The cube that launches forms a criss-cross structure.Although this technology illustrates the projection of a plurality of views with identical frame, the structure of layout is difficult to imitate and have the black region that disturbs viewing area.Therefore, when cube is unfolded, appears near the polyp in cube edge and divided at two or more windows.

Another kind of known technology adopts the integral surface to observing sphere to carry out visual mapping projection.Adopt Mercator (Mercator) and stereographic projection, the surface transformation of ball is to smooth surface.The major defect of this technology be since any projection on the surface of ball all on a plane, this has introduced the distortion to a certain degree of image.Especially, when showing the object in contiguous equator with minimum distortion, Mercator projection is mapped to the infinite distance with the utmost point of the earth.Need a kind of method that be used for producing the panorama endoscopic views from the volumetric image that shows view effectively and have a minimum distortion.

Brief summary of the invention

The present invention is intended to a kind of system and method for panoramic projection of the volumetric image that is used to produce object.Virtual camera is placed in the center of the cubic space of object inside.Be projected on the single plane from the image that camera obtained.Front image is mapped in the window at planar central place.Left and right, the top of cubic space and bottom diagram look like to be mapped to rectangular window around, make left and right, top and bottom diagram picture form consecutive image around rectangular window.

Description of drawings

The preferred embodiments of the present invention are described in detail the wherein same same element of reference number indication below with reference to accompanying drawing:

Fig. 1 illustrates a kind of prior art that is used to produce the projection of colon image;

Fig. 2 is for being used for producing from the volumetric image of colon the system chart of the system of panoramic view according to the present invention;

Fig. 3 illustrates the panoramic projection according to colon image of the present invention;

Fig. 4 illustrates the panoramic projection of colon image according to another embodiment of the present invention;

Fig. 5 illustrates the method that is used for producing from the volumetric image of colon the dish type panoramic view according to the present invention;

Fig. 6 illustrates according to square panoramic view of the present invention;

Fig. 7 illustrates the method that is used for seeking from the cube coordinate that launches direction vector according to the present invention;

The zone that Fig. 8 can't see after the image of colon being shown and using the standard camera projection to fall back and passing through; With

The zone that Fig. 9 can't see after the image of colon being shown and using panoramic projection of the present invention to fall back and passing through.

Embodiment

The present invention is intended to a kind of system and method that is used for producing from the volumetric image of object the panorama endoscopic views.To use medical image system the patient to be carried out aspect the medical inspection present invention is described.More specifically, will (Computed Tomography, CT) system carries out virtual coloscope inspection aspect present invention is described at the fault imaging that uses a computer.

One skilled in the art will appreciate that the present invention can use the two dimension or the 3-D imaging system of any kind that is used to observe patient's inner structure.These structures can comprise the structure of organ, blood vessel, tissue regions or other definition.The patient can be the human or animal.In addition, because filtrator is defined and is used for than higher-dimension and 2D, this method can be applied to the image of dimension arbitrarily.

The present invention also can be used to relate to the non-medical applications of two dimension or three-dimensional imaging.Such example can be the perhaps safe examination of parcel or other involved objects in being used for determining.Such system can be used to the postal delivery environment, perhaps is used in the examination airport or the adjunct in the place of other high safeties.The present invention also can have commercial Application, and is used to check or counts article manufactured or assembling.

The present invention utilizes the panoramic projection of the volumetric image of object, makes observer (for example doctor or medical science technician) not having under the situation of barrier and really to be positioned at the maximum that the mode of observed object inside is observed the surface with a kind of observer seemingly.Panoramic projection is designed to increase the surperficial visibility during the virtual endoscopy.The present invention produces a kind of projection, and described projection is rendered as a plane in a continuous manner with five faces in stereoscopy space.Because it has avoided must two-wayly passing through colon and having prevented the obstruction of potential polyp after the colon folds, use this visualization technique can significantly reduce estimated time as screening method to the colon cancer patient.

Fig. 2 has schematically described the system according to exemplary CT of the present invention.Can be used to the patient is carried out the noninvasive program with at different medical conditions examinations with CT system that computer aided detection (CAD) combines.The example of this program is to having the virtual coloscope inspection or the chest examination of the living tissue of damage or possibility cancer.One skilled in the art will appreciate that other image modes can be used under situation about not departing from the scope of the present invention with spirit.For example, magnetic resonance imaging (MRI), zyglo or ultrasonic imaging also can be used to obtain image.For illustrative purposes, will present invention is described using the CT system aspects.

The CT system disposition has the x-ray source 1 of emission cone type X-ray bundle 2, and the marginal ray of described X-ray beam is represented by penetrate checked object 3 (for example patient) and the dot-and-dash line that is mapped on the radiation detector 4 in Fig. 2.In this exemplary embodiment, x-ray source 1 is installed on the skirt 7 relative to one another with radiation detector 4.

But x-ray source 1 forms the gauging system that system for winding axle 8 rotates thus with radiation detector 4, make patient 3 can with respect to the different projection angles of described system axle 8 and along the diverse location place of system's axle 8 by x-ray bombardment.The synthetic output signal of independent detector element is read by data-acquisition system 10.This signal is sent to the signal processor 12 of the image that calculates patient 3, and this image can be shown on monitor 13 again.

By the CT system scan be transferred to CAD system 20 by the image that signal processor 12 calculates and be used for further processing.20 pairs of these image applications filtrators of CAD system are with the image that meets with a response.This then is used to produce the candidate.Feature then is collected (comprising the feature that derives from the filtrator value) and is used to described candidate classification from the candidate is the true or false positive.The candidate who only is categorized as true positives just is presented to the doctor.

According to the present invention, the rear-projected in the employed cube observation space is not shown.Virtual camera is placed in the center of solid space, and image is projected in the single plane with the viewing angle of 90 degree.As shown in Figure 3, according to the present invention, front image is mapped in the rectangular window of planar central, and other four images are projected in the trapezoidal window.This method has solved the discontinuity problem (see figure 1) that exists in the prior art, simultaneously the examination space that utilizes better.As in Fig. 3 as can be seen, the center of image 310 is central view of camera.Look and seek for left view 302, top view 304, right view 306 and bottom view 308 around this.The layout of view provides real more colon perspective internal view.

A kind of quick transmission of radiation algorithm is used to reproduce in real time each frame.Image 312 is the single frames during the crossing sequence.Owing to producing unique distortion of introducing by projection to the mapping of trapezoidal projection from cube body wall.In order to limit the distortion of the cubical edge that appears at expansion, according to another embodiment of the present invention, can use another kind of projection.Fig. 4 illustrates a kind of panoramic view, and wherein front 410 is mapped in the square, and other four sides 402-408 is mapped in the disk around this square.Projection has guaranteed the smooth transition around five faces.The size of front view can be conditioned.

The method that is used for producing from volumetric image panoramic projection is described in more detail referring now to Fig. 5-7.As shown, the axle of image coordinate system is marked as x, y and z.The x axle extends from the dextrad left side of image.The y axle extends to the top from the bottom of image.The z axle extends to the front portion from the rear portion of image.The panorama endoscopic views is by obtaining from the center projection radiation that is positioned over the virtual endoscope in the volume.The intensity of the point in the endoscopic views is the arbitrary function along the bulk strength value of corresponding ray.

From given endoscopy position, each bar ray is by the unique sign of direction vector.Like this, panoramic view is modeled as vector field (being the set of direction vector).This vector field is calculated at fixing endoscopy position.Suppose that endoscope is placed on the initial point of volume coordinate system and points to the z direction.By the translation and the rotation of vector field, any part of endoscope and direction can be considered.

Above-described two kinds of panoramic views (being dish type and square view) are the improvement that prior art is launched the cube view.These panoramic views are designed to obtain continuous projection, big visual field and limited distortion.

According to the present invention, projection is the process of one two step.At first, for each point in the panoramic view, find the point of the correspondence in one of cubical that launches.The second, find corresponding direction vector.

Fig. 5 illustrates according to the method on the continuous panoramic projection to of the cube disk that is used for launching of the present invention.Endoscopic views is modeled as a disk, and it is inscribed within the square that the length of side is L (promptly the radius of this disk equals L/2).Arbitrfary point in this square is by the position vector with respect to its center

Characterize.The inner length of side is the cubical front view of the square of l corresponding to expansion.The other parts of disk comprise the form after the conversion of the cubical top of expansion, left and right and bottom view.

As shown in Figure 5, introduce four vectors:

Term v (j) represents vector

J ingredient, and

Be its norm.Expressing | x| represents the absolute value of scalar x.Operational symbol is corresponding to the product of two scalars.

Coordinate system is affixed to cubical each face (wherein (0,0) is 1 for the upper left corner of face and the length of side) of expansion.On a given face, as shown in Figure 5, point is by one group of coordinate (r, c) location.Mapping between disk and cubical is as follows:

If

, the set-point intensity level is 0 (point is positioned at outside the disk) so

Otherwise

If $\mathrm{MAX}\left(\right|p\left(1\right)|,|p\left(2\right)\left|\right)<\frac{1}{2}$ So

(point is positioned at inner square-" front portion " view)

(what is corresponding coordinate?)

$r=0.5+\frac{p\left(1\right)}{l}$

$c=0.5+\frac{p\left(2\right)}{l}$

Otherwise

(point is positioned at lateral plan)

(which view?)

If

So

(point is positioned at " top " view)

( With

Between the cosine of angle)

(

Be positioned at the length of the part of inner square)

Else if So

(point is positioned at " right side " view)

[... ] (same principle is applied to new direction)

Else if So

(point is positioned at " left side " view)

[... ] (same principle is applied to new direction)

Else if

So

(point is positioned at " bottom " view)

[... ] (same principle is applied to new direction)

Finish

Finish

Finish

Fig. 6 illustrates according to of the present invention the continuous panoramic projection of cube the launched method to the square.The dimetric projection view is a kind of modification of disk projection view, and wherein the cube of Zhan Kaiing is mapped on the square.Do not have remaining areas not to be used, but have some distortions along the diagonal line of endoscopic views.Mapping between square and cubical is as follows:

If $\max \left(\right|p\left(1\right)|,|p\left(2\right)\left|\right)<\frac{1}{2}$ So

(point is positioned at inner square-" front portion " view)

Is (what corresponding coordinate?)

$r=0.5+\frac{p\left(1\right)}{l}$

$c=0.5+\frac{p\left(2\right)}{l}$

Otherwise

(point is positioned at lateral plan)

(which view?)

If

So

(point is positioned at " top " view)

(

With

Between the cosine of angle)

(

Be positioned at the length of the part of inner square)

Else if

So

(point is positioned at " right side " view)

[... ] (same principle is applied to new direction)

Else if

So

(point is positioned at " left side " view)

[... ] (same principle is applied to new direction)

Else if

So

(point is positioned at " bottom " view)

[... ] (same principle is applied to new direction)

Finish

Finish

The following description is with reference to figure 7, and Fig. 7 illustrates the method that is used for seeking from the cube coordinate that launches direction vector.Frustum (frustum) is corresponding to cubical each face (seeing Fig. 5 and Fig. 7) that launches.(be positioned at apart from the endoscope position is d to frustum by frontal plane _AnteriorThe length of side is l _AnteriorSquare) and back plane (being positioned at apart from the endoscope position is d _{The rear portion}The length of side be l _{The rear portion}Square) characterize.

Next how explanation seeks cube wherein simultaneously upward corresponding to position (r, the direction vector of ray c)

With " top " view is example; Can be directly applied for other view.

Order

(see figure 3)

And

(see figure 3)

Then

Should be understood that above-described method can be merged to obtain compacter and effective enforcement.The symmetry of vector field also can be utilized with minimizing and assess the cost.

In order to prove validity of the present invention, will utilize the number percent of the visual colon surface of standard camera projection to compare with utilizing the visual colon surface of panoramic projection of the present invention.One way is carried out in each projection passed through virtual colon.Fig. 8 illustrates and uses traditional virtual camera to be projected in the global view that reverse direction is passed through colon afterwards.The Dark grey pixel is represented sightless zone.

Fig. 9 illustrates the identical result who passes through who uses panoramic projection of the present invention.Because these projections show preceding, left and right, upper and lower view simultaneously, thereby the current surface coverage that has near 100% of one way.

For the coverage rate that obtains, traditional virtual navigation is typically carried out additional passing through on other direction.Additional passing through not only because surperficial some parts has increased time for reading detected twice, and even some zones still be hidden in after the colon folds.Because the number of times that passes through can be reduced half, so panoramic projection can be used to quicken 3D and reads.One skilled in the art will appreciate that panoramic projection of the present invention is not limited to the inspection to colon, and can be used to show the surface, inside of any virtual organ.

The embodiment of method that is used to produce the panoramic view of volumetric image is described, it should be noted, those skilled in the art can change and change according to above-mentioned instruction.Should be understood that thus, in disclosed specific embodiment of the present invention, can fall into by changing in the appended scope and spirit of the present invention that claim limited.In details with aspect the desired characteristic of Patent Law the present invention has been described, and desired and wish to obtain being illustrated in the appended claims of patent certificate protection.

Claims (27)

1, a kind of method of panoramic projection of the volumetric image that is used to produce object may further comprise the steps:

A virtual camera is placed at center in the cubic space of object inside;

Will be to single plane from image projection that camera obtained;

Front image is mapped in the window at planar central place; With

With left and right, the top of cubic space and bottom diagram look like to be mapped to rectangular window around, make left and right, top and bottom diagram picture form consecutive image around rectangular window.

2, the described method of claim 1, wherein left and right, top and bottom diagram look like to be mapped in the trapezoidal window.

3, the described method of claim 2, wherein left and right, top and bottom diagram picture and front image form a square-shaped image when mapped.

4, the described method of claim 1, wherein left and right, top and bottom diagram look like to be mapped in the angled fan-shaped window.

5, the described method of claim 4, wherein left and right, top and bottom diagram picture and front image form a dish type image when mapped.

6, the described method of claim 1, wherein in object inside along single direction mobile virtual camera.

7, the described method of claim 6 wherein when virtual camera during at the object internal motion, all produces panoramic projection to each picture frame subsequently.

8, the described method of claim 7, wherein the ray projective technique is used to reproduce each picture frame fast.

9, the described method of claim 1, wherein the size of front image can be conditioned.

10, the described method of claim 1, wherein object is a human organ.

11, the described method of claim 10, wherein human organ is a colon.

12, the described method of claim 11, the computed tomography (SPECT) system that wherein uses a computer obtains image.

13, a kind of method of panorama endoscope projection of the volumetric medical images that is used to produce virtual colon may further comprise the steps:

A virtual camera is placed at center in the cubic space of virtual colon inside;

Virtual colon is passed through in execution;

When passing through virtual colon, virtual camera obtains sequence of image frames;

To during passing through, project on the single plane from each picture frame that virtual camera obtained;

Front image is mapped in the rectangular window at planar central place; With

With left and right, the top of cubic space and bottom diagram look like to be mapped to rectangular window around, make left and right, top and bottom diagram picture form consecutive image around rectangular window.

14, the described method of claim 13, wherein left and right, top and bottom diagram look like to be mapped in the trapezoidal window.

15, the described method of claim 14, wherein left and right, top and bottom diagram picture and front image form a square-shaped image when mapped.

16, the described method of claim 13, wherein left and right, top and bottom diagram look like to be mapped in the angled fan-shaped window.

17, the described method of claim 16, wherein left and right, top and bottom diagram picture and front image form a dish type image when mapped.

18, the described method of claim 13, wherein in object inside along single direction mobile virtual camera.

19, the described method of claim 18 wherein when virtual camera during at the object internal motion, all produces panoramic projection to each picture frame subsequently.

20, the described method of claim 19, wherein the ray projective technique is used to reproduce each picture frame fast.

21, the described method of claim 13, wherein the size of front image can be conditioned.

22, the described method of claim 13, the computed tomography (SPECT) system that wherein uses a computer obtains image.

23, a kind of system of panorama endoscope projection of the volumetric medical images that is used to produce virtual colon comprises:

Virtual camera, it is placed on the center of the cubic space of virtual colon inside, and this virtual camera is carried out and is passed through virtual colon to obtain sequence of image frames;

Processor, be used for and during passing through, project to a single plane from each picture frame that virtual camera obtained, this processor front image is mapped in the rectangular window at planar central place and with left and right, the top of cubic space and bottom diagram look like to be mapped to rectangular window around, make left and right, top and bottom diagram picture form consecutive image around rectangular window; With

Display is used for display image.

24, the described system of claim 23, wherein left and right, top and bottom diagram look like to be mapped in the trapezoidal window.

25, the described system of claim 24, wherein left and right, top and bottom diagram picture and front image form a square-shaped image when mapped.

26, the described system of claim 23, wherein left and right, top and bottom diagram look like to be mapped in the angled fan-shaped window.

27, the described system of claim 26, wherein left and right, top and bottom diagram picture and front image form a dish type image when mapped.

Images