Patent Application
20110038518
This application claims priority of German application No. 10 2009 037 242.3 filed Aug. 12, 2009, which is incorporated by reference herein in its entirety.
The invention relates to a method for the superimposed representation of images, for instance a roadmap method, in which, original images are recorded in a first phase during the system dose regulation phase and then x-ray images are recorded during a second phase, for instance a filling phase, in which the vessels are filled with contrast agent, from which roadmap images develop following if necessary further image processing.
For a diagnostic examination and interventional procedures in the field of cardiology for instance, radiology and neurosurgery are used to image interventional x-ray systems, the typical essential features of which may be a robot controlled C-arm, to which an x-ray tube and an x-ray detector are attached, a patient support couch, a high voltage generator for generating the tube voltage, a system control unit and an imaging system including at least one monitor. A C-arm x-ray system of this type shown in
By means of the articulated robot 1 known from U.S. Pat. No. 7,500,784 B2 for instance, which preferably comprises six axes of rotation and six degrees of freedom, the C-arm 2 can be adjusted spatially in an arbitrary fashion, for instance by being rotated about a rotation center between the x-ray emitter 3 and the x-ray detector 4. The inventive x-ray system 1 to 4 can be rotated in particular about a rotation center and axes of rotation in the C-arm plane of the x-ray image detector 4, preferably about the axes of rotation intersecting the center point of the x-ray image detector 4 and about the center point of the x-ray image detector 4.
The known articulated robot 1 has a base frame, which is fixedly mounted to a floor for instance. A carousel is rotatably fastened thereto about a first axis of rotation. A robot lever is pivotably attached to the carousel about a second axis of rotation, to which robot lever a robot aim is rotatably fastened about a third axis of rotation. A robot hand is rotatably attached to the end of the robot aim about a fourth axis of rotation. The robot hand comprises a fastening element for the C-arm 2, which can be pivoted about a fifth axis of rotation and rotated about a sixth axis of rotation which proceeds at right angles thereto.
The realization of the x-ray diagnostics facility is not dependent on the industrial robot. Conventional C-arm devices can also be used.
The x-ray image detector 4 may be a rectangular or quadratic, flat semiconductor detector, which is preferably made from amorphous silicon (a-Si). Integrating and possibly numerative CMOS detectors can however also be used.
A patient 6 to be examined is positioned as an examination object on a patient support couch 5 for recording a heart for instance in the radiation path of the x-ray emitter 3. A system control unit 7 comprising an imaging system 8 is connected to the x-ray diagnostics facility, said imaging system 8 receiving and processing the image signals of the x-ray image detector 4 (control elements are not shown for instance). The x-ray images can then be observed on a monitor 9.
Different imaging methods are used nowadays in interventional vascular radiology, which assist with moving or positioning interventional objects “IOs” such as wires, coils, balloons, stents, prostheses, catheters etc. in the vessel tree. These are so-called roadmap methods. In this way the vessel tree recorded at a preceding point in time is superimposed using the current fluoroscopy, during which the IO is moved. These may be the following methods for instance:
Classical Roadmap:
DSA-Based Roadmap:
A suitable DSA image is used here for the mask.
3-D-Based Roadmap:
All these methods have a common feature; the two data records, at least the mask image and the current image of the active fluoroscopy series, are achieved in the local space, in other words by mixing the gray scale values of both data records. Here the dark wire of the current fluoroscopy is superimposed onto the bright vessel tree of the mask image for instance. With the pixel-by-pixel superimposition, the addition of the one original image A to a certain percentage μ to the other original image B,
C(i,j)=μ·A(i,j)+(1−μ)·B(i,j)
causes the new, superimposed roadmap image C to lose contrast in each pixel (i,j). The dark wire becomes less dark, the bright vessel loses brightness.
This also generally applies if gray scale value adjustments are subsequently still performed in the case of the resulting roadmap image C, like for instance gray scale value windowing, or if more complex superimposition techniques are used in the local space (and/or gray scale value space), which may alternatively be used. Current conventional methods of this type are explained in more detail with the aid of
The object underlying the invention is to improve the superimposed representation of images according to the roadmap method of the type cited in the introduction in an easy fashion.
The object is achieved in accordance with the invention for a method and for an apparatus by the features specified in the independent claims. Advantageous embodiments are specified in the dependent claims.
The object is achieved in accordance with the invention for a method by the following steps:
A temporal “superimposition” is achieved as a result, so that no complicated connections are needed. Also no contrast of the individual images gets lost.
It has proven advantageous if the processing of the individual original images according to step b) involves an inversion of one of the original images, a sharpening and/or a general gray scale value adjustment being implemented.
In accordance with the invention, the first original image may be a mask image and the second original image may be a current fluoroscopy image.
Advantageously, for representation purposes, at least one original image can be derived from an original image sequence as a second original image.
In accordance with the invention, several original images can be routed for a consecutive representation.
It has proven advantageous if the original images are created with at least one medical imaging system from the group comprising x-ray system, CT system, MR system, ultrasound system and/or PET system, with the original images corresponding in terms of their projection.
A flickering of the images is prevented if the representation takes place with an increased frequency compared with the reproduction frequency.
If necessary, the average and/or general gray scale value of the two original images or original image sequence n is to be matched to one another in order to further reduce the impression of the flickering.
The object is achieved in accordance with the invention for an apparatus comprising
It has proven advantageous for the image processing to be embodied such that an inversion of one of the original images, a sharpening and/or a general gray scale value adjustment can be implemented.
In accordance with the invention, the medical imaging system can be selected from the group comprising x-ray system, CT system, MR system, ultrasound system and/or PET system.
The invention is described in more detail below with the aid of exemplary embodiments shown in the drawing, in which:
The inventive roadmap method for the superimposed representation of images is now shown in more detail with the aid of
The main idea was now to propose a temporal “superimposition” in order to improve the superimposition of two original images (current fluoroscopy image and mask image). In this process the original images A and B possibly remain separate at first in order to be processed to form roadmap images A′ 16 and B′ and/or roadmap sequence B′n 18. This can take place for instance by, inter alia, inverting one of the original images A or B, sharpening or general gray scale value adjustment. The roadmap images A′ 16 and B′ and/or roadmap image sequence B′n 18 are then shown alternately one after the other, i.e. presented alternately to the eye with high frequency, with attention having to be paid to the correct position on the monitor by means of the selected projection. Here the original contrast of each original image is essentially retained. Therefore here the superimposition takes place in the brain and not on the plane of the image processing. By alternately representing the images, they can be used originally, i.e. the full contrast is retained.
If individual images 10 and 11 (A and B) are shown as temporally superimposed in each instance, the roadmap images 16 and 18 (A′ and B′) are easily consecutively reproduced (following a separate image processing). In some instances, this takes place with a higher frequency than in the case of a representation of only one image, in order to prevent flickering.
If an individual original image A 10 and an original image sequence Bn 11 or original image series are to be superimposed, the roadmap image 16 (A′) is shown respectively between a roadmap image 18 (B′) of the original image sequence Bn (n=1, N) 11. To prevent the impression of flickering, the process must be carried out at in some instances with an image reproduction frequency which is higher than usual. Nowadays, x-ray images for instance, which are recorded with a recording frequency of 15 B/s or also only 4 B/s, are shown with 30 B/s for instance or also considerably higher in the case of the image reproduction. This generally results in a repeated image representation. The images are then each shown 2 and/or 8 times per second in this example. Here the roadmap image A′ 16 and the roadmap image B′n 18 are always shown alternately in the case of the image repetition.
With the new method, on account of the original acquisition frequency of the original image sequence B for instance or for optophysiological reasons, a higher, possibly double frequency must be shown since the mask image must still additionally be shown occasionally in each instance.
If necessary, the general gray scale value of the two original images or original image sequence n is to be matched to one another in order to further reduce the impression of flickering.
Flickering may occur as a result of two things:
There must be no “subtraction images”. The important thing is essentially that the image reproduction frequency is selected so high that the “superimposition” goes on in the head.
The roadmap method can be expanded to the superimposition of any medical images, which match in terms of their projection. For instance, an alternating representation 14 of x-ray and CT images, x-ray and MR images, CT and ultrasound images, MR and ultrasound images and/or MR and PET images etc. is also possible.
Instead of two images or images sequence n in each instance, several images or image sequences n of different modalities can at the same time also be alternately superimposed. The images must then be displayed consecutively in each instance and the frequency is possibly further increased.
This is illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2009 037 242.3 | Aug 2009 | DE | national |
