IMAGING SYSTEM FOR DISPLAYING A STRUCTURE OF TEMPORALLY CHANGING CONFIGURATION
FIELD OF THE INVENTION The present invention relates to an imaging system for use in monitoring a structure having a configuration which changes with time, such as for example a functioning heart.
BACKGROUND OF THE INVENTION
The stretching of the Left Ventricle (LV) during the cardiac cycle is known to be related to cardiac health. Imaging technology enables static volume (3D) images and dynamic volume (4D) images to be generated. Cardiac imaging systems such as Ultrasound, CT or MRI Imaging have been developed to image the LV during the cardiac cycle. A specific ultrasound imaging technique is disclosed in WO2004003851.
A useful modality of visualisation has now been devised.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a modality of visualisation enabling an observer to interact with and/or observe an image display providing useful technical understanding of how a structure changes in configuration over time.
According to a first aspect, the invention provides an imaging system for displaying image data representative of a structure of temporally changing configuration, the system comprising display rendering means for processing data representative of the changing configuration of the structure and rendering a display comprising a reference image of the structure in a predetermined configuration and superposing with the reference image a changing image of the structure which changes in configuration with respect to time.
The invention therefore enables the provision of a moving sequential image of the changing configuration structure with respect to a reference image. This aids in both qualitative and quantitative review. The invention has particular application in relation to cardiac evaluation, but the skilled addressee will readily appreciate that the invention has application in reviewing other structures that have a configuration that changes over time.
Beneficially, the system includes data acquisition means for acquiring the data representative of the structure configuration as it varies with time. In one embodiment, the system may include ultrasound imaging apparatus for acquiring the data. The acquisition means preferably acquires 3D volume, data for processing.
According to another aspect, the invention provides a method of rendering image data representative of a structure of temporally changing configuration, the method comprising processing data representative of the changing configuration of the structure and rendering a display comprising a reference image of the structure in a predetermined configuration and superposing with the reference image a changing image of the structure which changes in configuration with respect to time.
The reference image is preferably a static image of the structure, remaining static whilst the configuration of the changing image changes with respect to time.
The system preferably comprises a 3D imaging system and the reference image and/or the changing image is beneficially a 3D rendered image.
The temporally changing structure typically changes in configuration cyclically and the changing image beneficially represents the cyclically changing 3D volume of the structure. Beneficially the reference image represents the maximum volume of the structure. For example, the structure monitored may comprise the Left Ventricle (LV) of a heart, in which case the reference image is beneficially representative of the LV End Diastole (ED).
The image reviewed is beneficially the boundary of the structure, and to this end the data represents the boundary of the structure.
In a specific realisation, the invention provides a method of imaging the Left Ventricle (LV) of a heart comprising rendering a display comprising a reference image of the LV in End Diastole and superposing with the reference image a changing image of the LV through the heart beating cycle.
According to a further aspect, the invention provides a computer program product comprising a set of instructions enabling performance of the method.
These and other aspects of the invention will be apparent from and will be elucidated with reference to the embodiments described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described in more detail, by way of example, with reference to the accompanying drawings, wherein:
- Figure 1 is a schematic flowchart representing operation of a system in accordance with the present invention, - Figure 2 is an ultrasound image of the LV of a patient's heart showing the computer generated border,
Figure 3 shows a series of 3D mesh frames of the LV at different time periods within the cardiac cycle, superposed with the 3D ED mesh, Figure 4 is a schematic representation of the data acquisition system.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings, figure 1 shows a flowchart of steps taken in a technique according to the invention to generate a visualisation of the LV beat. The LV of a patient is initially monitored (block 100) using conventional monitoring techniques such as ultrasound imaging and or ECG, to ascertain the ED (end-diastole) phase (block 110) of the cardiac cycle.
In an exemplary technique a 3D echocardiography system could be utilised. The system having means for acquiring a digital image sequence, and is associated to a digital processing system for processing the acquired 3D volume data. The examination system 550 shown in figure 4 comprises means for providing image data to the processing system which has at least one output 506 to provide image data to display and/or storage means 530,540. The display and storage means may respectively be the screen and memory of a workstation 510. The workstation 510 may also comprise a keyboard 531 and a mouse 532.
The image processing system 520 may be a suitably programmed computer of a workstation 510, or a special purpose processor having circuit means such as filters, logic operators, memories that are arranged to perform the functions of the method steps according to the invention. The processing system 520 may use a computer program product having program
instructions to be executed by the computing means of the processing system 520 in order to carry out the method steps.
Following the 3D volume acquisition, the 3D image data corresponding to the LV at the ED phase of the cardiac cycle is processed to generate a computed border 400 of the LV, as seen in figure 2.
A computer algorithm then prompts a user to select a series of points (block 120) within the computer generated border and then uses the information to generate a 3D mesh (block 130) that completely covers the area of the image within the border and thus specifies the surface of the LV. (This segmentation technique is related to the Finite Element Method, which is one of several standard mathematical techniques used in the analysis of image data). In this manner, a reference mesh is obtained for the ED phase of the LV during the cardiac cycle. If necessary the computer generated mesh can be modified at this stage (block 140).
The ES (End-Systole) (block 200) phase of the LV is then ascertained in a similar manner with the border of the LV again being determined (block 210) and the corresponding mesh generated (block 230) through the user selecting a series of points (block 220). Again this mesh can be modified if necessary (block 240).
Following the determination of the ED (block 100) and ES (block 200) phases of the cardiac cycle, the border of the LV is determined from a sequence of 3D images within the cardiac cycle at selected time intervals (block 300) from ED to ES (block 310), and the corresponding mesh is generated automatically (block 320), which if necessary can be modified (block 330).
In accordance with the invention, the system then renders an image display having a reference image of the structure in a preselected configuration (the ED phase of the LV), superposed with the changing image of the structure as it changes with respect to time.
Thus, by playing the acquired mesh frames in succession, the 3D LV border can be displayed as a live beating object and when displayed within the ED reference mesh, clear departures can be seen between the current frame and the reference frame 500 during the cardiac cycle (figure 3). Furthermore, the superposition of meshes also highlights any global movement the
LV may undertake during for example, respiration. Such visualisation images provide a collective account of the motion of the surface of the LV as it changes with respect to time and therefore, in contrast to the prior art in which only one frame time is shown, the visualisation illustrates the changes of the LV border over the whole heart cycle.
It is to be understood that whilst the image visualisation has been presented here in the form of a mesh, further visual remedies are also possible which do not depart from the scope of the invention. Thus, it should be realised that the reference mesh and temporally changing mesh are simply representative of an image. The data could equally be manipulated to generate other representations of the surface of the LV.
It is also to be understood that whilst an ultrasound imaging technique has been primarily described, the invention can be used to manipulate and display image data obtained using other techniques such as for example Magnetic Resonance Imaging (MRI) or Computed Tomography (CT).
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.