Patent Application
20100315487
This application claims priority under 35 U.S.C. §119(a)-(d) or (f) to prior-filed, co-pending French patent application number 0953952, filed on Jun. 12, 2009, which is hereby incorporated by reference in its entirety.
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1. Field of the Invention
The present invention relates to imaging.
It more particularly concerns imaging methods in which views corresponding to 3D representations of an observation region are superimposed over 2D images of the same observation region.
2. Description of Related Art
Fluoroscopy techniques are conventionally used in interventional radiology in particular to allow real-time viewing, during a procedure, of 2D fluoroscopic images of the region in which the procedure is being carried out. The surgeon is therefore able to take bearings for navigation in vascular structures and to check the positioning of instruments and their deployment.
With the so-called 3D Augmented Fluoroscopy technique or “3DAF” this information is completed by superimposing, over the 2D image, a 2D view of a previously acquired 3D image of the observation region containing the structure or organ in which procedure is being conducted.
Under the present invention, “2D view” means a representation in a plane of a 3D representation.
This 2D view is calculated for this purpose so that it corresponds to the same acquisition geometry as defined by the 2D fluoroscopic image over which it is superimposed. One example of this type of processing is notably described in the patent application “Method and apparatus for acquisition geometry of an imaging system” (US 2007-0172033).
The information given to the practitioner by this superimposed display remains limited however, since the 2D view is calculated for only one acquisition geometry i.e. that of the 2D fluoroscopic image.
The present invention concerns a medical imaging method using at least one 2D image of a patient's observation region acquired by an imaging device defining an acquisition geometry, a region for which there exists a 3D representation, characterized in that the method comprises the determination of at least 2D views of the 3D representation following the acquisition geometry of the imaging device for at least two different viewing points of the observation region, so as to allow the superimposition of the 2D image with each 2D view.
If the view is a volume view entailing management of hidden parts, the information given is different and complementary since if part A hides part B for one viewing point, part B will hide part A for the opposite viewing point.
This then provides the practitioner both with a front 2D view and a back 2D view of the parts of the structure or organ, without it being necessary to change the viewing angle and hence the acquisition geometry of the fluoroscopic 2D image.
Preferred, but non-limiting, aspects of the method of the invention are the following:
In one embodiment for example, the images being acquired using apparatus with a conical radiation source:
A geometric conversion matrix is applied to the previously acquired original 3D representation, such that all the rays leaving the focal point of the source and passing through the 3D representation following the acquisition geometry before conversion are parallel after conversion.
And in the converted 3D representation, a view is determined following a parallel viewing geometry, equivalent to the acquisition geometry in the original 3D representation, and from a viewing point at which the depth is defined from the image formation plane of the acquisition geometry (front view).
Under another embodiment:
If the focal point is infinity, the case is the simple case in which the acquisition geometry is parallel and in which geometric conversion of the 3D representation is identical.
The invention also concerns a medical imaging system comprising an imaging device defining an acquisition geometry and allowing the acquisition of at least one 2D image of an observation region in a patient, a region for which there exists a 3D representation, noteworthy in that the system comprises means to determine at least two 2D views of the 3D representation following the acquisition geometry of the imaging device for at least two different viewing points of the observation region, so as to allow superimposition of the 2D image with each 2D view.
The invention also concerns a medical imaging system comprising a radiation source and an acquisition sensor of 2D images, at least one memory to store at least one previously acquired 3D image, a processing unit which determines a front view in said 3D image from a same viewing angle as for the 2D image, a display screen on which said processing unit displays the superimposition of said 2D image and said front view, the system being noteworthy in that said processing unit further determines a back view in said 3D representation said view being superimposable over the 2D image.
The invention also concerns a computer programme product comprising programming instructions able to determine a back view in a 3D image, the back view being from the same viewing angle as the 2D image, characterized in that the programming instructions, in said 3D image, are also able to determine a front view of said 3D image, and to display a superimposition of the front view and the 2D image.
Other characteristics and advantages of the invention will become further apparent from the follow description which is solely illustrative and is non-limiting, and is to be read with reference to the appended figures in which:
a and 4b are examples of anterior (or front) images and posterior (or back) images obtained using a method according to
a and 5b are examples of front and back views obtained using a method according to
The apparatus shown in
As is conventional, the C-arm is able to be pivoted about the axis of a table (4) intended to receive the patient to be imaged, and to be moved relative to this table 4 in different directions schematized by the double arrows in the figure, so as to allow adjustment of the positioning of said arm relative to that part of the patient that is to be imaged.
The source (2) is an X-ray source for example. It projects conical radiation which is received by the sensor (3) after passing through the patient to be imaged. The sensor (3) is of matrix array type and for this purpose comprises an array (3) of detectors.
The output signals from the detectors of the array (3) are digitized and they are received and processed by a processing unit (5) which optionally stores in memory the digital 2D images thus obtained. Before and after processing, the digital 2D images thus obtained can also be memorized separately from the processing unit (5), any medium possibly being used for this purpose: CD-ROM, USB key, mainframe memory, etc.
As is conventional for example, prior to the procedure a set of 2D images is acquired of the patient organ on which procedure is to be performed by rotating the C-arm around the patient. The set of 2D images obtained is then processed to calculate a 3D representation of the organ concerned by procedure. Processing operations to isolate a given organ and to determine a 3D representation from a set of 2D images are conventionally known per se.
Display of a 2D view of the 3D representation is then made using a given viewing geometry containing a viewing angle direction z, a direction orthogonal to the plane of formation of the 2D view and whose origin defines the viewing point. Direction z therefore defines a depth relative to the viewing point such that the foreground planes are defined for z values close to 0 and the more distant planes by z's of higher value. The 3D representation points which correspond to the x, y coordinates in the formation plane of the 2D view orthogonal to the viewing direction z are projected in relation to their depth z in said direction. For this purpose, for each coordinate point x, y of the 2D view to be displayed a buffer depth memory is formed in which the voxels of the 3D representation are memorized in relation to their depth z. This buffer depth memory is itself processed so that the displayed 2D view shows those parts of the 2D view which are in the foreground and does not show the hidden parts (background). Said processing is conventionally known per se.
The 2D view of the 3D representation can be displayed superimposed over a 2D image whose acquisition geometry is known, for example a fluoroscopic image acquired in real-time during a procedure. One example of such processing is notably described in the patent “Method for the improved display of co-registered 2D-3D images in medical imaging” (US 2007/0025605).
As illustrated in
During a first step (A1) a geometric conversion matrix is applied to the original 3D representation in memory, this matrix intended to allow viewing in parallel geometry equivalent to viewing using the conical acquisition geometry of the radiation of source (2) for the original 3D representation.
As effectively illustrated in
During a second step (B1), the value of a point is determined in the 2D view which it is desired to display by projecting in parallel from a back viewing point (
Another manner of proceeding, illustrated
Both manners of proceeding are equivalent and in both cases allow a front 2D view (7) of the 3D representation to be obtained which, as is usual for the back 2D view (8), can be displayed by being superimposed over the fluoroscopic 2D image.
This therefore provides the practitioner with two 2D views (7, 8) superimposed over the fluoroscopic 2D view: one a front view (7), the other a back view (8) of the organ on which procedure is being performed.
These two 2D views of the 3D representation, which are superimposed over the fluoroscopic 2D image, can be displayed successively or simultaneously on the display screen, one beside the other.
Examples of front and back 2D views 7, 8 obtained in this manner are given in
It will be appreciated that said display of 2D views of the 3D representation corresponding to front and back 2D views provides practitioners with better perception of their surgical movements.
As an example, when treating multilobar intercranial aneurysms, the lobes can be viewed on either side of the head for better apprehending of the aneurysm being treated.
Additionally, said front and back display has the advantage of helping the practitioner to solve some positioning ambiguities of instruments. For example, in electrophysiology, by being able to view the catheter tip from two different 2D views, the surgeon is able to better identify the heart area where the instrument is positioned.
As will be understood, the processing just described is performed digitally, by unit 5 for example, the results being displayed on a display screen 5a of said unit. The programming instructions corresponding to this processing can be memorized in dead memories of unit 5 or in any suitable data processing medium: CD-ROM, USB key, memory of a remote server, etc.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0953952 | Jun 2009 | FR | national |
