WO2007049207A1

WO2007049207A1 - System and method for generating for display two-dimensional echocardiography views from a three-dimensional image

Info

Publication number: WO2007049207A1
Application number: PCT/IB2006/053873
Authority: WO
Inventors: Pau Soler
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2005-10-27
Filing date: 2006-10-20
Publication date: 2007-05-03
Also published as: JP2009513221A; CN101297326A; EP1952359A1

Abstract

A system and method for generating for display a number of standard 2D echocardiographic views from 3D image data acquired in respect of a subject. In one embodiment, a medical practitioner positions the 3D probe so that one visualisation plane corresponds to a standard 2D view and then pre-calculated relative coordinates are used to automatically locate and generate other standard 2D views. Alternatively, a landmark extraction algorithm is used to identify specific features, from which the respective visualisation planes can be located and the standard 2D views generated.

Description

SYSTEM AND METHOD FOR GENERATING FOR DISPLAY TWO-DIMENSIONAL ECHOCARDIOGRAPHY VIEWS FROM A THREE-DIMENSIONAL IMAGE

The invention relates to a system and method for generating and displaying standard two-dimensional echocardiography views, and a corresponding diagnostic display apparatus.

Two-dimensional ultrasonic imaging is used as an important non-invasive technique in the comprehensive characterization of a number of body organs. In ultrasonic imaging, a sound pulse is sent along a ray from a transducer towards the organ that is being imaged. The pulse is attenuated and reflected when it hits a medium with an acoustic impedance different from that of the medium in which the pulse is travelling. The time the sound pulse takes in transit is a measure of the distance of the medium interface from the transducer. The amount of energy that is reflected is a measure of the difference in acoustic impedance across the interface. Assuming that the pulse travels at a single speed in the body, and by taking rays uniformly distributed across a given plane, a two- dimensional record of the received energy in spatial (Cartesian, polar) coordinates can be used to present a cross-sectional view of the imaged organ.

Echocardiography is the application of ultrasonic imaging to the heart. Echocardiography has experienced widespread acceptance in the evaluation of cardiac disease, structure and function of the heart. This acceptance is in large part due to its noninvasive nature, and to its real-time capability for observing both cardiac structure and motion. Using echocardiography, quantitative information may be obtained concerning cardiac anatomy, chamber diameter and volume, wall thickness, valvular structure, ejection fraction, etc. However, the technique of imaging the heart using ultrasound waves presents some limitations. For example, ultrasound waves cannot penetrate ribs, therefore a limited field of view is onbtainable from transthoracic examinations. Furthermore, tissues parallel to the ultrasound beam are not very reflective, resulting in a poor tissue delineation, and ultrasound waves are attenuated through their propagation, therefore a limited depth can be imaged.

Current medical practice overcomes these limitations by obtaining different scans of the heart through different acoustic windows, i.e. different anatomical points where the probe is placed, typically between the ribs.

Currently, 2D echocardiography is the most popular imaging technology. 2D echocardiography is the transmission of ultrasound beams (by a one dimensional array of ultrasonic transducers) at a series of angles to interrogate a sector of a plane. The image thus obtained displays a slice of the heart at its intersection. Standard echocardiographic views have been defined by clinical protocol and referring to Figure 1 of the drawings, typical views include (a) parasternal long axis, (b) parasternal short axis, (c) apical four- chamber, apical two chamber, sub-costal, etc. Moreover, the probe angle can be adjusted to obtain the best tissue delineation. Medical practitioners usually combine these different views for a complete heart diagnosis, and it takes quite some time to obtain all of the necessary images from the various respective viewpoints.

The recent introduction of 3D ultrasonic imaging systems has enabled new capabilities and protocols in the field of echocardiography. For example, US Patent No.6, 352,509 describes a 3D ultrasonic diagnosis apparatus which performs a 3D acquisition of a subject's heart, identifies in the acquired 3D image data the cardiac cavity region and then displays the image data acquired in respect of that region. Some of the standard 2D views referred to above may be contained in a single 3D acquisition, and a medical practitioner can scan through such a 3D acquisition to search for the appropriate information. Moreover, 3D ultrasound imaging systems also enable volume renders to be generated, whereby the whole 3D data set can be viewed, rather than just 2D slices. In this case, it is necessary to select a region of interest to look at notable features. Typical notable features include the mitral valve from inside the left ventricle, the tricuspid valve and apical four chambers. Once again, however, it takes the medical practitioner quite some time to scan through the 3D image data and select the appropriate fields of view for diagnosis.

Nevertheless, 3D echocardiography is gaining increasing support within the medical community for use in diagnosis and treatment of various heart conditions, including diagnosis of numerous valve pathologies such as mitral stenosis, mitral prolapse, mitral flail, mitral regurgitation, aortic stenosis, aortic regurgitation and ischemias, among others.

It is an object of the present invention to provide a system and method for generating for display a number of different two-dimensional images from various viewpoints in respect of a structure of interest, whereby the time and effort required to obtain such images is significantly reduced relative to prior art arrangements. It is also an object of the invention to provide a corresponding display system.

In accordance with the present invention, there is provided a system for generating for display, a plurality of predetermined two-dimensional images at different respective coordinates in respect of a structure or volume of interest, the system comprising means for receiving three-dimensional image data acquired in respect of said structure or volume of interest, means for automatically determining respective coordinates corresponding to one or more predetermined viewpoints in respect of said structure or volume of interest, and means for generating from said three-dimensional image data respective two-dimensional images from said one or more predetermined viewpoints.

Also in accordance with the present invention, there is provided a method for generating for display, a plurality of predetermined two-dimensional images at different respective coordinates in respect of a structure or volume of interest, the method comprising receiving three-dimensional image data acquired in respect of said structure or volume of interest, automatically determining respective coordinates corresponding to one or more predetermined viewpoints in respect of said structure or volume of interest, and generating from said three-dimensional image data respective two-dimensional images from said one or more predetermined viewpoints.

Thus, the present invention provides means to automatically obtain the standard 2D echocardiographic views from a 3D image data acquisition, and to display these 2D echocardiographic views together with 3D render views, also obtained from the same 3D image data acquisition, this results in a faster examination process (typically a ratio of four to one) and facilitates the diagnosis task, since these 2D views contain the most relevant information.

In one embodiment, the system may further comprise means for receiving user- selected data representative of a first predetermined viewpoint, and means for calculating from said data respective coordinates of one or more further predetermined viewpoints. Such user- selected data is preferably derived by manual placement relative to said structure or volume of interest of means for capturing said three-dimensional image data. Thus, the medical practitioner manually situates the 3D probe so that one visualisation plane coincides with a standard 2D view, say the apical four-chamber, and other standard views are obtained using coordinates pre-calculated by the system.

In an alternative embodiment, the system comprises means for identifying within said three-dimensional image data one or more features of said structure or volume of interest and calculates therefrom the respective coordinates corresponding to said one or more predetermined viewpoints. Thus, all of the 2D the view coordinates can be determined without the medical practitioner' s intervention.

The two-dimensional images beneficially correspond to predetermined two- dimensional echocardiographic views.

The present invention extends to a display apparatus for displaying images of a structure or volume of interest, the apparatus comprising a system as defined above for generating a plurality of two-dimensional images at different respective coordinates in respect of said structure or volume of interest, and display means for displaying said two- dimensional images.

The apparatus may further comprise means for generating and displaying three - dimensional image data, such as one or more 3D render views, in respect of said structure or volume of interest.

These and other aspects of the present invention will be apparent from, and elucidated with reference to, the embodiments described herein.

Embodiments of the present invention will now be described by way of examples only and with reference to the accompanying drawings, in which:

Figures l(a) - (c) illustrate schematically the acquisition of a 2D echocardiographic plane and the resultant image in respect of the parasternal long axis, the parasternal short axis and the apical four-chamber 2D views respectively;

Figure 2 is a schematic block diagram illustrating the principle features of a system according to a first exemplary embodiment of the present invention; and

Figure 3 is a schematic block diagram illustrating the principle features of a system according to a second exemplary embodiment of the present invention.

Referring to Figure 2 of the drawings, in a first exemplary embodiment of the present invention, 3D image data is acquired (at 10) in respect of the subject's heart. The medical practitioner performing the examination is required to position the ultrasonic probe (at 12) during the 3D image acquisition process such that one of the 3D planes coincides with a standard 2D view, such as an apical four-chamber. This can be done simply by viewing the current image on a screen and adjusting the position of the probe relative to the subject such that the desired view is obtained. Once this view has been obtained, the coordinates for this view can be set to (0,0) and pre-calculated relative coordinates are used (at 14) to determine the coordinates corresponding to other standard 2D views, such as the apical two-chamber 16, the parasternal long axis 18 and the parasternal short axis 20. These views are displayed on a screen 21, together with, for example, a 3D render 22 of the mitral valve.

This manual mode has the benefit of being extremely fast and robust. Although it may not be quite as accurate as the automatic mode to be described below, it provides a goo and fast starting point for the visualisation. Even if the medical practitioner wants to refine the displayed views, most of the work has already been done. On the other hand, the medical practitioner must monitor the position of the original apical four-chamber to keep the images in its frame.

Referring to Figure 3 of the drawings, in an alternative exemplary embodiment of the invention, an unsupervised scheme is proposed, whereby the system relies on an automatic landmark detection algorithm (at 24) to determine the coordinates for, and generate the 2D views, in respect of, say, the apical four-chamber 12, the apical two- chamber 16, the parasternal long axis 18 and the parasternal short axis 20. These views are displayed once again on a screen 21, together with, for example, a 3D render 22 of the mitral valve. The automatic landmark detection algorithm may, for example, identify valves, the mitral annulus, apex or any other characteristic feature of the heart within the acquired 3D image data. Once the position in space has been determined, the standard 2D views can be displayed accordingly. In other words, pre-calculated relative coordinates may be applied once specific landmarks have been identified.

This mode of operation has the benefit of operating unsupervised, so from a good 3D acquisition, 2D and 3D standard views can be automatically extracted. This reduces the acquisition time relative to prior art systems and also enable practitioners with less experience to obtain good scans. It is also faster in terms of human-machine interaction. On the other hand, the computational cost of this embodiment of the invention is dependent on the complexity of the feature extraction algorithm, which in turn has an effect on the length of time it might take to start the system. It will be apparent to a person skilled in the art that there are a number of algorithms that could be used to extract landmarks, including fast ones such as "k-means" segmentation for detecting structure walls, "k-means" segmentation of difference images for valves, but also more complex ones such as those based on level-sets or differential equations. Other types of feature extraction algorithm are envisaged to be suitable for use for this purpose, and the present invention is not necessarily intended to be limited in this regard. For example, the Haigh transfer is a well known feature extraction technique used in digital image processing to detect shapes, such as circles. The classical transfer identifies lines in an image, but it has been extended to identify positions of arbitrary shapes, such as circles. By detecting circles in the axial planes, it is possible to find the main axis of the left ventricle. Velocity maps provide another example for automatically detecting landmarks. The principle of velocity maps consists in performing the difference of different frames, e.g. v(x,O) = i(x,O) - i(x,l) where i(x,t) is the image frame at time t and x is the position in space. Basically, the points x where v is bigger correspond to the points which move the most, i.e. the valves. It will be appreciated that another more robust estimate than simply this difference, could be used. In fact, many other means for automatically detecting landmarks will be apparent to a person skilled in the art.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be capable of designing many alternative embodiments without departing from the scope of the invention as defined by the appended claims. In the claims, any reference signs placed in parentheses shall not be construed as limiting the claims. The word "comprising" and "comprises", and the like, does not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The singular reference of an element does not exclude the plural reference of such elements and vice- versa. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. A system for generating for display, a plurality of predetermined two-dimensional images at different respective coordinates in respect of a structure or volume of interest, the system comprising means for receiving three-dimensional image data acquired in respect of said structure or volume of interest, means for automatically determining respective coordinates corresponding to one or more predetermined viewpoints in respect of said structure or volume of interest, and means for generating from said three- dimensional image data respective two-dimensional images from said one or more predetermined viewpoints.

2. A system according to claim 1, further comprising means for receiving user- selected data representative of a first predetermined viewpoint, and means for calculating from said data respective coordinates of one or more further predetermined viewpoints.

3. A system according to claim 2, wherein said user- selected data is derived by manual placement relative to said structure or volume of interest of means for capturing said three-dimensional image data.

4. A system according to claim 1, further comprising means for identifying within said three-dimensional image data one or more features of said structure or volume of interest and means for calculating therefrom the respective coordinates corresponding to said one or more predetermined viewpoints.

5. A system according to claim 1, wherein said two-dimensional images correspond to predetermined two-dimensional echocardiographic views.

6. A method for generating for display, a plurality of predetermined two-dimensional images at different respective coordinates in respect of a structure or volume of interest, the method comprising receiving three-dimensional image data acquired in respect of said structure or volume of interest, automatically determining respective coordinates corresponding to one or more predetermined viewpoints in respect of said structure or volume of interest, and generating from said three-dimensional image data respective two- dimensional images from said one or more predetermined viewpoints.

7. A display apparatus for displaying images of a structure or volume of interest, the apparatus comprising a system as defined above for generating a plurality of two- dimensional images at different respective coordinates in respect of said structure or volume of interest, and display means for displaying said two-dimensional images.

8. Apparatus according to claim 7, further comprising means for generating and displaying three-dimensional image data in respect of said structure or volume of interest.