WO2010070532A2

WO2010070532A2 - Positioning a cut plane in respect of a three-dimensional image

Info

Publication number: WO2010070532A2
Application number: PCT/IB2009/055578
Authority: WO
Inventors: Yi Zhang; Njin-Zu Chen
Original assignee: Koninklijke Philips Electronics NV
Current assignee: Koninklijke Philips NV
Priority date: 2008-12-16
Filing date: 2009-12-08
Publication date: 2010-06-24
Anticipated expiration: 2011-06-16
Also published as: WO2010070532A3

Abstract

A system for positioning a cut plane in respect of a three-dimensional image comprises visualizing means (1) for providing a visualization of the three-dimensional image and the cut plane according to a viewing direction. Rotating means (3) enable a user to control a rotation of the three-dimensional image in respect of the cut plane and in respect of the viewing direction, leaving an orientation of the cut plane fixed with respect to the viewing direction. Positioning means (4) position the cut plane parallel to the viewing direction, for example vertically in the visualization with respect to an orientation of a user. Shifting means (5) enable a user to shift the cut plane with respect to the three-dimensional image

Description

Positioning a cut plane in respect of a three-dimensional image

FIELD OF THE INVENTION

The invention relates to positioning a cut plane in respect of a three- dimensional image, in particular a medical image.

BACKGROUND OF THE INVENTION

Three-dimensional images are datasets comprising information of objects in a three-dimensional space. Such information can comprise location, shape, and/or appearance. Such three-dimensional images may be visualized in many ways using a viewing application. Such viewing applications may allow interactive visualization, allowing a user to manipulate the image and/or the visualization thereof. Common interaction possibilities include rotating, zooming, and panning of the image with respect to a viewing direction. Another common possibility is to provide a cut plane, which is a plane intersecting the image. Such a plane can be used to create sectional views of the image. Interactive positioning of a cut plane is experienced as a difficult task by many end users, in particular when the structure which is being visualized is complex.

US 2003/0095120 Al discloses a method comprising defining a cut plane through the volume and displaying a pair of axial images, one image representing a first sub- volume from a first direction whereas the other image represents a second, complementary sub- volume from the opposite direction. A freely selectable point of rotation in the visualized volume is defined through which the cut plane extends and about which the cut plane can also be rotated. Preferably, this point of rotation is defined at locations with important object details, for example, in complex vascular deformations such as, aneurysms, AVMs, or stenoses, but also in the vicinity of bone fractions.

However, using the known method, it is still difficult to position the cut plane.

SUMMARY OF THE INVENTION

It would be advantageous to have an improved system for positioning a cut plane in respect of a three-dimensional image. To better address this concern, in a first aspect of the invention a system is presented that comprises visualizing means for visualizing the three-dimensional image and the cut plane according to a viewing direction; and rotating means for enabling a user to control a rotation of the three- dimensional image in respect of the cut plane and in respect of the viewing direction, leaving an orientation of the cut plane fixed with respect to the viewing direction.

The rotating means as proposed makes it easier to make a cut in the way desired. It was found that rotating the volume, leaving the cut plane in a fixed position, is an easier task for the user than manipulating the cut plane directly. The task of rotating a volume with respect to the plane may be experienced as a natural form of interaction by the user, because it corresponds to real- life manipulation of objects such as cutting vegetables, wherein a vegetable to be cut may be rotated before cutting, while the knife is kept in the same direction.

Positioning means may be provided for automatically positioning the cut plane parallel to the viewing direction. The cut plane parallel to the viewing direction corresponds to the metaphor of cutting food with a knife on the kitchen table. In the kitchen example, the plane in which the cut takes place may be downward, perpendicular to the kitchen table. Viewing the cutting operation from above, the cut plane is parallel to the viewing direction. By orienting the cut plane with respect to the viewing direction in a manner which allows the user to refer to real- life experience, the process of positioning the cut plane is made easier. The positioning means may be arranged for positioning the plane vertically in the visualization with respect to an orientation of a user. The vertical orientation is regarded as particularly natural, corresponding to a common position of a knife when slicing vegetables.

Shifting means may be provided for enabling a user to shift the cut plane with respect to the three-dimensional image. The shifting, or moving, of the cut plane while keeping the orientation of the cut plane fixed with respect to the three-dimensional image, may be offered to the user as a relatively straightforward operation and in addition to the functionality of rotating the three-dimensional image. The shifting means may be arranged for keeping the position of the three-dimensional image fixed with respect to the visualization while shifting the cut plane. This keeps the interaction relatively simple.

Second visualizing means may be provided for providing an additional visualization of the three-dimensional image and the cut plane from a viewing direction oblique or perpendicular to the cut plane. The additional visualization provided by the second visualization means may be in addition to the visualization of the visualization means set forth. The additional visualization helps to quickly assess the cut.

The system set forth may be included in a medical imaging workstation or in a medical image acquisition apparatus. It will be appreciated by those skilled in the art that two or more of the above- mentioned embodiments, implementations, and/or aspects of the invention may be combined in any way deemed useful.

Modifications and variations of the image acquisition apparatus, of the workstation, of the system, and/or of the computer program product, which correspond to the described modifications and variations of the system, can be carried out by a person skilled in the art on the basis of the present description.

A person skilled in the art will appreciate that the method may be applied to multidimensional image data, e.g., to 2-dimensional (2-D), 3-dimensional (3-D) or 4- dimensional (4-D) images, acquired by various acquisition modalities such as, but not limited to, standard X-ray Imaging, Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Ultrasound (US), Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT), and Nuclear Medicine (NM).

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention will be further elucidated and described with reference to the drawing, in which

Fig. 1 is a block diagram of a system for positioning a cut plane in respect of a three-dimensional image;

Fig. 2 is a block diagram of a method of positioning a cut plane in respect of a three-dimensional image;

Figs. 3 through 6 are sketches illustrating aspects of a visualization of a three- dimensional image and a cut plane.

DETAILED DESCRIPTION OF EMBODIMENTS Limitations may be imposed on possible ways in which a user can move a plane in respect of a three-dimensional object, both the plane and the three-dimensional object being objects in a computer graphics scene. These limitations may reduce confusion of a user relating to the question of how to position the plane in a particular way. Moreover, a user can be provided with an auxiliary image showing the result of the cut in order to reduce the overall operation effort.

Nowadays, clinical personnel, such as physicians, use more and more 3D viewing applications. Some of these viewing applications may for example be used during the intervention procedures to facilitate efficient and effective patient treatments. Other viewing applications may for example be used in a viewing room. The viewing applications provide plentiful functions, so that physicians are able to look into the vessels to plan and apply the treatments. Such viewing applications may provide a cut functionality. After a 3D volume image is constructed from raw detector data, physicians typically want to focus on a subset of that data that is relevant for the treatment or diagnosis at hand. They may use cut functions to remove any irrelevant portion and keep only the relevant data. In this way, a more appropriate view may be obtained. In this description, a number of techniques are described in relation to a volume dataset. However, this is not a limitation. Most techniques apply to a three-dimensional image in general. Such a three-dimensional image may comprise a volumetric dataset, or volume image, but it may also comprise, for example, a surface model of a structure. A volume image typically associates intensity levels with points, or volume elements, in a three-dimensional volume. Such intensity levels may represent objects, such as a vascular structure or an organ.

One of the possible cut functions is 'cut plane'. With this function, a user can position a plane and cut away the portion in the volume image on one side of the plane. This plane can be rotated or moved by means of user interaction functionalities, using mouse input, for example. The 3D volume can also be rotated or moved together with the plane.

However, positioning the plane may be a difficult task for a user. One of the reasons for this is that the mapping of the rotation commands provided to the system may cause confusion. Also, it may be difficult to assess the current rotation angle and position of the cut plane in the visualization of the scene.

Moreover, it may be difficult to predict the results of the cut. For example, only one side of the 3D object being cut may be shown at any time. To view the cut from the other side, a user may have to rotate the volume (together with the plane) to view the cut plane from the other side. Such an operation costs extra time and might have a negative impact on the user's confidence.

By lowering the difficulty of the 2D plane control and by providing a relatively simple way to view the results of the cut, the 'cut plane' function is made easier to use. This may improve the effectiveness and/or efficiency of the cut plane functionality. The metaphor of cutting a vegetable, for example an onion, in a kitchen may be used to obtain a simplified interaction for positioning a cut plane. An onion in the kitchen may be cut using the following process. First, the onion is put on the kitchen sink. The user observes the onion from above. The blade of the kitchen knife is positioned on top of the onion with the sharp side facing downward. The user observes the knife as a vertical line with the onion below it. Next, the user pushes the blade down, cutting the onion in two parts. Some aspects of this scenario can be simulated to make the process of positioning a cutting plane in a medical image easier. The plane may correspond to the blade of the knife and the objects in the volume image may correspond to the onion to be cut. When slicing the onion, the knife may be moved from side to side, while the onion is kept in place. At some point, when the cutting process becomes awkward, the orientation of the onion may be changed by rotating it to a different angle, and then the cutting may be continued. During the procedure, two movements are involved, the rotation of the onion and the translation of the knife. Similarly, it would be 'natural' for a user to be able to rotate the volume, keeping the cut plane in place. It would also be 'natural' for a user to be able to translate the cut plane in respect of the volume. It would also be 'natural' for a user if the cut plane were kept in an upright (i.e. vertical) position with respect to the user. It may help already if only one or only some of these features were implemented in a cut plane tool.

For example, the user interface may allow a user to rotate the volume and translate the cut plane. The functionality to rotate the cut plane may be omitted. The functionality to translate the volume may also be omitted. Omitting these two functionalities may make the interaction more intuitive for some users. However, other users may prefer to be offered these functionalities as well. For example, it may be allowed to rotate and move the volume, but only translate the plane. An auxiliary visualization may be provided in addition to the visualization set forth (the latter being referred to hereinafter as the 'main visualization'). In this additional visualization, the cut plane may be visualized from the side. For example, the cut plane may be visualized from an oblique angle, slightly different from the main visualization, allowing a user to see the result of the cut. Moreover, two auxiliary visualizations may be provided, showing the cut plane from different sides.

Fig. 1 shows a block diagram of a system for positioning a cut plane in respect of a three-dimensional image. The system may, for example, be implemented at least partly in software, for being executed on a computer system. The system can also be implemented in a dedicated electronic circuit. When implemented in a computer system, such as a medical workstation or a console of an imaging acquisition apparatus, the system may comprise a processor for executing instructions of the software code, a storage means, including for example one or more of: RAM, ROM, hard drive, removable media, DVD, CD-ROM. Such storage means can be used to store the software and/or to store image data and patient information, for example. It is also possible to store coordinates of a cut plane in respect of a three-dimensional image, or to store a snapshot showing a visualization of a three- dimensional image with a cut plane applied thereto. Also, a communication port may be provided for input and output of image data, patient data, control data, user input data, and other kinds of data. Such communication port may be connected to a network connection to for example a LAN, WLAN, or the Internet.

A display 7 may be provided for displaying visualizations of a three- dimensional scene, and for displaying menu items and control icons. A scene control unit 6 may be provided for maintaining coordinates of positions and orientations of objects in a computer graphics scene. Examples of such objects are a three-dimensional image, or a cut plane. Other examples are arrows or annotations which may be provided in the scene and defined in respect of the three-dimensional image. The scene control unit 6 may be arranged for providing an initial scene comprising a three-dimensional image and a cut plane intersecting the three-dimensional image. Also a snapshot storage 8 may be provided for storing a snapshot of a visualization generated by visualizing means 1 or 2. Another option is to store the coordinates of a cut plane as provided by the scene control unit 6. A dataset representing a three-dimensional image 9 may be provided. This dataset may be obtained from a medical image acquisition apparatus such as a 3D Rotational Angiography x-ray apparatus, a CT scanner or an MR scanner. The three-dimensional image 9 may be a volume image, which assigns intensity levels to volume elements (voxels). The three-dimensional image 9 may also comprise a geometric object, such as a surface shape model. User input device 10 may comprise a keyboard and/or a mouse. Other user input devices such as haptic feedback devices may also be used.

The system may comprise visualizing means 1 for providing a visualization of the three-dimensional image and the cut plane according to a viewing direction. The visualizing means 1 applies computer graphic techniques to generate such a visualization, usually a two-dimensional rendering of the three-dimensional scene. The visualization may be displayed on the display 7 or stored in the snapshot storage 8.

The system may comprise rotating means 3 for enabling a user to control a rotation of the three-dimensional image in respect of the cut plane and in respect of the viewing direction. The rotating means 3 keeps an orientation of the cut plane fixed with respect to the viewing direction applied by the visualization means 1 during generating the visualization. The rotating means may receive and process events generated by the user input device 10. Some events may be translated by the rotating means 3 into a rotation operation of the three-dimensional image. The rotation operation may be performed by providing the scene control unit 6 with new orientation parameters of the three-dimensional image. Such orientation parameters can comprise a quaternion representing a rotation, or angles of rotation around three orthogonal axes, for example.

The system may comprise positioning means 4 for positioning the cut plane parallel to the viewing direction. This positioning may be performed automatically. The positioning means 4 may be arranged for automatically positioning the cut plane in the way set forth, upon entering a cut plane mode. As a result of this, the cut plane may be visible in the visualization as a line, for example. The positioning means 4 may be arranged for positioning the cut plane vertically in the visualization with respect to an orientation of a user. This could result in a visualization of a vertical line representing the cut plane.

The system may comprise shifting means 5 for enabling a user to shift the cut plane with respect to the three-dimensional image. If the cut plane is vertical, this can result in the cut plane moving to the left or to the right. The shifting means may be arranged for receiving events triggered by the user input device 10. Some events may be translated by the shifting means 5 into shift operations. The shifting means 5 may be coupled to the scene control unit 6. The shifting operation may be realized by providing the scene control unit 6 with the new position of the cut plane.

The system may comprise second visualization means 2 for providing an additional visualization of the three-dimensional image and the cut plane from a viewing direction oblique or perpendicular to the cut plane. For example, a second viewport on the display 7 may be provided in which the additional visualization is displayed.

The several means described above may be configured for being activated in response to a user command received via user input 10. Such activation may activate a 'cut plane' mode, in which the cut plane may be initialized by the positioning means 4 and which allows to adapt the cut by rotating the three-dimensional image and shifting the cut plane in the way set forth. The 'cut plane' mode may be exited by another command to be received via user input 10. After exiting said 'cut plane' mode, the cut plane may be frozen with respect to the three-dimensional object. The cut plane as a geometric object may not be visualized any more, but the portion of the three-dimensional image on one side of the cut plane may be hidden in further visualizations. Such hiding may also optionally be performed by either one or both visualization means 1 and 2, while still positioning the cut plane.

The system set forth may be included in a medical workstation or in a medical image acquisition apparatus. Fig. 2 illustrates a method of positioning a cut plane in respect of a three- dimensional image. The method may include a step 101 of providing a visualization of the three-dimensional image and the cut plane according to a viewing direction, and a step 102 of enabling a user to control a rotation of the three-dimensional image in respect of the cut plane and in respect of the viewing direction, leaving an orientation of the cut plane fixed with respect to the viewing direction. The method allows being implemented as a computer program product comprising computer instructions for causing a processor system to perform the steps of the method.

Fig. 3 through Fig. 6 illustrate an example of how a 'cut plane' may be manipulated. Similar objects have been labeled with the same reference numerals. Fig. 3 illustrates a visualization of a volume image 31 in an arbitrary orientation, the volume comprising an aneurysm 33 and vessels 34. At 35, it is indicated where the user intends to position a cut plane. The actual cut plane 32 may be positioned vertically in a plane parallel to the viewing direction. The plane may be generated automatically at the request of the user. By default, the plane may be placed in the centre of the image area, standing in the same direction with his view.

The user may give one or more commands to the system to rotate the volume. For example, command buttons may be provided to rotate the volume clockwise or counterclockwise around any of three perpendicularly chosen axes. It is also possible to map mouse movements to rotations about one or more axes, in a way known in the art per se. The volume may be rotated freely. The user would rotate the volume such that the position 35 where he would like to make a cut is more or less parallel to the plane 32. This situation is illustrated in Fig. 4.

Next, the user would translate the cut plane 32 in the direction of the aneurysm 33 containing the position 35 of the envisaged cut. To this end, the cut plane 32 is translated in the direction of the arrow 41. As shown in Fig. 5, the user positions the cut plane 32 on the desired position 35 on the aneurysm 33. Also, an auxiliary visualization 51 is provided enabling the user to inspect the result of the cut from a different point of view. This auxiliary visualization 51 shows a cross section of the neck 52 of the aneurysm corresponding to the cut plane 32. Fig. 6 illustrates a sketch of the situation after rotation of the volume image 31 in the direction of the arrow 53. This further improves the alignment of the cut plane 32 with the desired cut position 35.

The techniques described herein can be applied to 3D object manipulation and 3D modeling application. They may improve the ease of positioning a cut plane. It will be appreciated that the invention also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of a source code, an object code, a code intermediate source and object code such as a partially compiled form, or in any other form suitable for use in the implementation of the method according to the invention. It will also be appreciated that such a program may have many different architectural designs. For example, a program code implementing the functionality of the method or system according to the invention may be subdivided into one or more subroutines. Many different ways to distribute the functionality among these subroutines will be apparent to the skilled person. The subroutines may be stored together in one executable file to form a self-contained program. Such an executable file may comprise computer executable instructions, for example processor instructions and/or interpreter instructions (e.g. Java interpreter instructions). Alternatively, one or more or all of the subroutines may be stored in at least one external library file and linked with a main program either statically or dynamically, e.g. at run-time. The main program contains at least one call to at least one of the subroutines. Also, the subroutines may comprise function calls to each other. An embodiment relating to a computer program product comprises computer executable instructions corresponding to each of the processing steps of at least one of the methods set forth. These instructions may be subdivided into subroutines and/or stored in one or more files that may be linked statically or dynamically. Another embodiment relating to a computer program product comprises computer executable instructions corresponding to each of the means of at least one of the systems and/or products set forth. These instructions may be subdivided into subroutines and/or stored in one or more files that may be linked statically or dynamically.

The carrier of a computer program may be any entity or device capable of carrying the program. For example, the carrier may include a storage medium, such as a ROM, for example a CD ROM or a semiconductor ROM, or a magnetic recording medium, for example a floppy disc or hard disk. Further the carrier may be a transmissible carrier such as an electrical or optical signal, which may be conveyed via electrical or optical cable or by radio or other means. When the program is embodied in such a signal, the carrier may be constituted by such a cable or other device or means. Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circuit being adapted for performing, or for use in the performance of, the relevant method.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the 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 positioning a cut plane in respect of a three-dimensional image, comprising visualizing means (1) for providing a visualization of the three-dimensional image and the cut plane according to a viewing direction; and rotating means (3) for enabling a user to control a rotation of the three- dimensional image in respect of the cut plane and in respect of the viewing direction, leaving an orientation of the cut plane fixed with respect to the viewing direction.

2. The system of claim 1, further comprising positioning means (4) for automatically positioning the cut plane parallel to the viewing direction.

3. The system of claim 2, the positioning means (4) being arranged for positioning the cut plane vertically in the visualization with respect to an orientation of a user.

4. The system of claim 1, further comprising shifting means (5) for enabling a user to shift the cut plane with respect to the three-dimensional image.

5. The system of claim 4, the shifting means (5) being arranged for keeping the position of the three-dimensional image fixed with respect to the visualization while shifting the cut plane.

6. The system of claim 2, further comprising second visualization means (2) for providing an additional visualization of the three-dimensional image and the cut plane from a viewing direction oblique or perpendicular to the cut plane.

7. A medical workstation comprising the system of claim 1.

8. A medical image acquisition apparatus comprising the system of claim 1.

9. A method of positioning a cut plane in respect of a three-dimensional image, comprising providing (101) a visualization of the three-dimensional image and the cut plane according to a viewing direction; and enabling (102) a user to control a rotation of the three-dimensional image in respect of the cut plane and in respect of the viewing direction, leaving an orientation of the cut plane fixed with respect to the viewing direction.

10. A computer program product comprising computer instructions for causing a processor system to perform the steps of the method according to claim 8.