CN101849843B - Navigation method of three-dimensional cardiac ultrasonic virtual endoscope - Google Patents

Abstract

The present invention provides a three-dimensional echocardiographic virtual endoscopic navigation method, comprising the following steps: acquiring an initial two-dimensional slice image of the heart; reconstructing and displaying a three-dimensional view according to the two-dimensional slice image; setting a virtual endoscopic viewpoint that can be moved and controlled; and viewing is guided by movement of the virtual endoscopic viewpoint and an observation path is generated in said three-dimensional view. The method ensures that the observer is not easily lost while observing the tissue structure of the heart from multiple directions.

Description

Three-dimensional echocardiography virtual endoscopic navigation method

【Technical field】

The invention relates to the fields of computer medical imaging technology and navigation technology, in particular to a three-dimensional cardiac ultrasound virtual endoscope navigation method.

【Background technique】

Virtual endoscopy (virtual endoscopy, VE) is a new medical imaging technology currently developed, which uses computer virtual reality technology to generate three-dimensional visualization images with endoscopic visual effects. Combining virtual reality with visualization in scientific computing technology, using CT, MRI or ultrasound two-dimensional image data for three-dimensional visualization reconstruction, simulating the traditional endoscopic inspection process, and realizing roaming in human organs and even blood vessels, It can also perform flight observation along the virtual internal cavity, display continuous three-dimensional organ internal cavity structure diagrams, and generate visualized images with endoscopic simulation effects on the computer screen. This technology overcomes many disadvantages of ordinary endoscopes, such as coughing, nausea, or even wall perforation and bleeding caused by patients not adapting to endoscopes, and inexperienced doctors who control endoscopes moving in organs lose their direction and increase the pain of patients , and the structure of the endoscope itself cannot reach many important parts of the human body.

Since the first report of CT simulation bronchial endoscopy technology by Vining et al. in 1993, virtual endoscopy has combined virtual reality with scientific computing visualization technology and has been successfully applied to medical image processing. The virtual environment combines the user and the computer into a whole, and the user is placed in a three-dimensional electronic environment created by simulating the real world, producing an immersive interactive visual simulation.

However, the current application of virtual endoscopy in medicine mainly focuses on organs with cavity structures, such as gastrointestinal tract, bronchi, blood vessels, nasal cavity, inner ear, and so on. Because it is similar to fiberoptic endoscopy (Fiberoplic Endoscopy, FE), it is also called "simulated endoscopy". Virtual endoscopy is a non-invasive technology, which avoids the pain caused by cardiac catheterization to patients, and has no complications such as bleeding, perforation, and infection. VE can be operated repeatedly, observe repeatedly from any angle and position, and can easily pass through the stenosis to observe the situation after stenosis.

However, due to the complex internal anatomy and valve movement of organs such as the heart, when the observer observes and evaluates the region of interest, the virtual endoscope must not only provide interactive real-time multi-angle observation, but also require a virtual viewpoint The position is constantly changing for observation, so there may be inaccurate observation and disorientation when operating the virtual endoscope. Therefore, it is necessary to explore and establish a three-dimensional ultrasound virtual endoscope navigation method.

【Content of invention】

The purpose of the present invention is to solve the above-mentioned problems in the prior art, and provide a navigation method for a three-dimensional echocardiography virtual endoscope. When the observation position of the virtual viewpoint is constantly changing, the observer is not easy to get lost.

The purpose of the present invention is achieved by the following technical means:

A three-dimensional cardiac ultrasound virtual endoscope navigation method, comprising the following steps:

Obtain an initial two-dimensional slice image of the cardiac tissue structure;

reconstructing and displaying a three-dimensional view in three dimensions according to the two-dimensional section image;

providing a movable and controllable virtual endoscopic viewpoint in said three-dimensional view; and

A viewing path is generated in the three-dimensional view by movement of the virtual endoscopic viewpoint.

When the organ to be checked is the heart, an initial two-dimensional slice image of at least one complete cardiac cycle is acquired.

The step of creating a three-dimensional view also includes a step of selecting a region of interest. The step of selecting a region of interest (ROI) adopts a segmental analysis method, divides the region of interest into several, and determines the size of the region division according to the structure of these observation regions. The scope of the region of interest is determined according to the observation object. The ROI selection for the atrioventricular valve area and the atrioventricular septum area should be large, and the ROI selection for the aortic and pulmonary artery areas should be small.

The viewpoint of the virtual endoscope is set at the center of the cavity or the great blood vessel in the region of interest.

When the virtual endoscope viewpoint is controlled to move and observe, the region of interest is placed in the center of the viewer's line of sight, so that the three-dimensional view advances along the line of sight, and amplified multi-frames in which the tissue structure target in the heart is continuously approaching the viewer are generated image.

When the viewpoint of the virtual endoscope is controlled for stationary observation, by adjusting the viewing distance and viewing angle of the viewpoint of the virtual endoscope, observation can be made at any angle and at any position of the tissue structure in the heart.

The three-dimensional view imaging of the virtual endoscope viewpoint adopts the surface rendering method when moving to observe the tissue structure of the organ to be examined, and the three-dimensional view imaging of the virtual endoscope viewpoint adopts the volume rendering method when observing the tissue structure of the organ to be inspected statically.

The three-dimensional image displayed when the viewpoint of the virtual endoscope moves is saved and played back, and the path of observation is reproduced.

The viewpoint of the virtual endoscope can be observed through the saved three-dimensional image observation path or guided according to a preset guiding path, or can be guided according to the control of the observer.

The beneficial effect of the present invention is that the user manually controls the movement of the viewpoint of the virtual endoscope in the three-dimensional view, roams in the three-dimensional view of the intracardiac tissue in a human-computer interactive navigation mode, and allows continuous playback of the observed area, Reproduce the path generated by observing roaming at any angle, so as to obtain the virtual simulation endoscopic observation effect of organs, which is convenient for the observer to judge and is not easy to get lost.

【Description of drawings】

Fig. 1 is a schematic diagram of steps of a specific embodiment of the present invention;

Fig. 2 is a schematic diagram of a navigation interface in a specific embodiment of the present invention.

【Detailed ways】

The specific implementation of the three-dimensional cardiac ultrasound virtual endoscope navigation method provided by the present invention will be described in detail below with reference to the accompanying drawings.

The specific implementation method is as follows: step S101, obtain the initial two-dimensional section image of the cardiac tissue structure; step S102, select the region of interest; step S103, reconstruct and display the three-dimensional view in three dimensions; step S104, set a movable and controlled virtual endoscope viewpoint; step S105, guide observation and generate an observation path through the movement of the virtual endoscope viewpoint; step S107, playback the observation path.

When the organ to be inspected is the heart, the three-dimensional echocardiography has great advantages in displaying the intracardiac structure, valve movement, etc., the sampling is convenient, the image acquisition time is short, and the artifacts caused by breathing or heart movement can be reduced, and Echocardiography is cheap and cost-effective, while CT and MRI are expensive, take a long time for imaging, and are difficult to track the dynamic changes of the heart, and are not suitable for critically ill patients. Therefore, the present invention obtains the initial two-dimensional section image of the tissue structure of the organ to be examined through three-dimensional ultrasound.

Referring to FIG. 1 , in step S101 , an initial two-dimensional slice image of the cardiac tissue structure is acquired. When the organ to be checked is the heart, an initial two-dimensional slice image of at least one complete cardiac cycle is acquired.

In step S102, a region of interest is selected. The region of interest (region-of-interest ROI) is the range of the observation area selected by the operator. Image analysis is performed on all regions within the ROI on each frame of tomographic image through image cutting. Regions outside the ROI will not be included in the visualization range during navigation , to reduce disturbance to the observer.

According to the heart structure and motion characteristics, combined with Van Praagh's "segmental analysis method", three regions of interest were set, namely the atrioventricular valve region, the atrioventricular septal region, and the main and pulmonary artery regions. The range of ROI is determined according to the observation object, among which the ROI of the atrioventricular valve area and the atrioventricular septum area should be large, and the ROI selection of the aorta and pulmonary artery area should be small.

In step S103, the 3D reconstruction and display of the 3D view is performed. A three-dimensional view is created according to the region of interest selected in step S102, and regions outside the region of interest are not included in the visualization range of the observer. See Figure 2, which is a schematic diagram of the navigation interface after selecting the region of interest, in which the box on the left is the ROI area selection, the arrow points to the position of the viewpoint, and the viewpoint is in the left ventricle, and the diagram on the right is the corresponding aorta under manual navigation Valve, mitral valve virtual display results.

In other specific implementation manners, step S101 may directly enter step S103, and instead of selecting the region of interest, the user may navigate along a preset path.

In step S104, a movable and controllable virtual endoscopic viewpoint is set in the virtual display image. This virtual endoscope viewpoint allows movement in multiple directions up and down, left and right, and front and back according to the control of the observer. At the same time, the observed objects within the visualization range can also undergo spatial transformation at any angle. Preferably, the virtual endoscope viewpoint is set at the central position of the cavity or the large blood vessel in the observation region of interest to observe around, so that no deformed visual effect will be caused due to wall attachment.

In step S105, guide the observation and generate an observation path through the movement of the viewpoint of the virtual endoscope. The movement of the viewpoint of the virtual endoscope can be based on a preset guiding path or according to the control of the observer. The movement of the viewpoint of the virtual endoscope can also be selected. 3D images and viewing paths saved since.

When the virtual endoscope viewpoint is controlled to move and observe, the observation area of interest is placed in the center of the observer's line of sight, so that the three-dimensional view advances along the line of sight, and the enlarged multi-frame images of the tissue structure target in the heart are continuously approaching the observer.

For example, when observing the atrioventricular valve area of the heart, simulate the surgical path, and display it in three dimensions from the atrium to the ventricle, or observe from the apex to the atrium. , the dynamic real-time display of the atrioventricular valve tissue structure in front of the viewpoint, the complete observation of the atrioventricular valve shape and activity, and the spatial relationship between the mitral valve, tricuspid valve annulus, subvalvular structures and surrounding adjacent structures.

When observing the atrioventricular septal area of the heart, the viewpoint is located on both sides of the atrial and interventricular septum, and the line of sight and the septal tissue are either vertically viewed or viewed sideways at an angle. If there is a septal defect in the three-dimensional display, the viewpoint can be controlled by moving the right mouse button and keyboard Move to the direction of the defect, observe the anatomical position, shape, size of the defect and the relationship with the surrounding tissue structure. When the viewpoint quickly advances through the defect area and reaches the other side of the interval, the viewpoint can be reversed, and the distance and viewing angle can be changed further. Observe the spatial structure of septal defects and adjacent tissues.

When observing the aorta region of the heart, the ROI at the connection between the aorta and the ventricle is the center, and the viewpoint is located in the ventricular cavity to observe the aorta and pulmonary arteries. For the case of aortic overriding, the viewpoint is moved to the inside of the aorta and observed from the root of the aorta toward the ventricular cavity to display the proportion of the aorta overriding the ventricular septum and observe the anatomical location of the ventricular septal defect.

In step S106, the observed path is played back. The path of observation can be reproduced by saving and continuously playing back the three-dimensional images displayed when the viewpoint of the virtual endoscope moves. When the viewpoint advances with the support of the navigation system, the observer can "stop and go", and when the viewpoint stops on the walking path, the system allows the observer to look around with the help of keyboard keys, and the generated image is added to the A frame of animation in a sequence of images. After any step of roaming in the heart, the system can replay the observed path to realize video frame rate observation.

As a better technical solution, the three-dimensional view imaging of the virtual endoscope viewpoint adopts the surface rendering method when the virtual endoscope viewpoint moves to observe the tissue structure in the heart, and the three-dimensional view imaging method of the virtual endoscope viewpoint adopts the volume The volume rendering method.

The surface rendering method, also known as the indirect rendering method, is based on the extraction of two-dimensional image edges or contour lines, constructing intermediate geometric primitives (such as curved surfaces, planes, etc.) from the three-dimensional space data field, and fitting the three-dimensional object through geometric unit Structure, with the help of traditional graphics technology and hardware to achieve picture rendering. In the methods of 3D surface reconstruction of medical images, there are many different methods to generate isosurfaces directly from 3D volume data, the most representative of which is the Marching Cubes method. The visualized graphics constructed by the surface rendering method cannot reflect the whole picture and details of the entire original data field. The visualized mapping only maps some attributes in the original data to a plane or curved surface, but it can produce a relatively clear isosurface image, and can use existing Some graphics hardware implements the rendering function, which speeds up the generation and transformation of images, and is a commonly used visualization algorithm.

Volume Rendering is a 3D data visualization method that has developed rapidly in recent years. Volume rendering is completely different from surface rendering. It does not construct intermediate geometric primitives, but is directly generated from the 3D data field. The voxel is directly projected to the display plane by applying the visual principle. The field produces a two-dimensional image on the screen, also known as the direct volume rendering (Direct Volume Rendering) algorithm.

The purpose of volume rendering is to provide a voxel-based rendering technology, which is different from the traditional surface-based rendering, directly draws the processed data, and can draw every data point in the reconstructed 3D model , including data inside the heart muscle.

Virtual endoscopic imaging based on volume rendering technology adjusts the threshold, transparency, and endows artificial false colors and different light brightness. The reconstructed three-dimensional image of the inner surface of the heart cavity can display the internal details of the heart, and can retain the overall information of the heart. High quality and easy image post-processing.

The application of virtual endoscope system in analysis and diagnosis requires high imaging quality, and the ultimate goal is to achieve real-time accurate display and interactive operation. The research on 3D ultrasound image rendering shows that the comprehensive utilization of surface rendering and volume rendering will improve virtual Observation effect of endoscope. The surface rendering method can be used when navigating the viewpoint of the virtual endoscope, and the imaging is fast and the image is clear. When the viewpoint position does not move, the volume rendering method can be used. The volume rendering can display the subtle structure and shape, so that the region of interest can be provided more abundantly. And precise information, so that the observer can get a more satisfactory field of view observation effect.

Therefore, the three-dimensional view imaging of the virtual endoscope viewpoint adopts the surface rendering method when observing the tissue structure in the heart while moving, and uses the volume rendering method when observing the tissue structure in the heart statically, which can better achieve fast imaging and fine and realistic images.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, some improvements and modifications can also be made, and these improvements and modifications should also be considered Within the protection scope of the present invention.

Claims (9)

1. a three-D ultrasonic virtual endoscope air navigation aid is characterized in that, comprises following steps:

Obtain the original two-dimensional tangent plane picture of organ-tissue structure to be checked;

Create 3-D view according to described two-dimentional tangent plane picture;

A virtual endoscope viewpoint that can move and control is set in described 3-D view;

Mobile guiding by the virtual endoscope viewpoint is observed, when controlling the static observation of described virtual endoscope viewpoint, by adjusting sighting distance and the visual angle of virtual endoscope viewpoint, observe the arbitrarily angled of organ-tissue structure to be checked with at any part, described virtual endoscope viewpoint is observed or according to the observation person's control guiding observation according to the default Route guiding that instructs, the iso-surface patch method is adopted in the 3-D view imaging when mobile observation organ-tissue structure to be checked of virtual endoscope viewpoint, and object plotting method is adopted in the 3-D view imaging when static observation organ-tissue structure to be checked of virtual endoscope viewpoint; And

In described 3-D view, generate observation path.

2. three-D ultrasonic virtual endoscope air navigation aid according to claim 1 is characterized in that, when described organ to be checked is heart, obtains the original two-dimensional tangent plane picture of at least one complete cardiac cycle.

3. three-D ultrasonic virtual endoscope air navigation aid according to claim 1 is characterized in that, also comprises the step of selection viewing area interested in the step of described establishment 3-D view.

4. three-D ultrasonic virtual endoscope air navigation aid according to claim 3, it is characterized in that, the step of described selection viewing area interested adopts segmental analysis, interested viewing area is divided into several, and the size of dividing according to the significance level definite area of these viewing areas.

5. three-D ultrasonic virtual endoscope air navigation aid according to claim 3 is characterized in that, described virtual endoscope viewpoint is arranged at the center of cavity or the trunk of described viewing area interested.

6. according to claim 3 or 5 described three-D ultrasonic virtual endoscope air navigation aids, it is characterized in that, controlling described virtual endoscope viewpoint moves when observing, described viewing area interested is placed observer's sight line center, 3-D view is advanced along direction of visual lines, produce the multiple image of the constantly close observer's of organ-tissue structural object to be checked amplification.

7. three-D ultrasonic virtual endoscope air navigation aid according to claim 1, it is characterized in that, when controlling described virtual endoscope viewpoint and moving, judge virtual endoscope viewpoint position according to blood distribution and the blood flow direction of organ-tissue structure to be checked in the 3-D view.

8. three-D ultrasonic virtual endoscope air navigation aid according to claim 1 is characterized in that, the 3-D view that showed when described virtual endoscope viewpoint is moved is preserved and carried out playback, reproduces the path of observing.

9. three-D ultrasonic virtual endoscope air navigation aid according to claim 8 is characterized in that, described virtual endoscope viewpoint is observed by the 3-D view observation path guiding of preserving.

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