Patent Application
20090185657
This application claims priority of German application No. 10 2008 005 118.7 filed Jan. 18, 2008, which is incorporated by reference herein in its entirety.
The invention relates to a method for the geometric registration of an imaging device outside an object, in particular a radiation device, with a device emitting fan-shaped signals, in particular an ultrasound emitter, within the object.
Several imaging modalities are increasingly used consecutively in the case of interventional operations, in order to control the guidance of the interventional instruments. The aim here is to use the advantages of the respective modalities. One example of this is an intracardiac echocardiogram within electrophysiology, which is recorded in particular during ablations of atrial fibrillations. In this way, a registration of an intracardiac ultrasound emitter with an x-ray C-arm system arranged outside the patient is necessary. The acoustic waves used for imaging which have a fan-shaped form are characteristic here of the ultrasound emitter.
The object of the invention is to specify a method for the geometric registration of these imaging devices.
To achieve this object, a method is provided which has the following steps:
A registration of the imaging device outside the object with the device emitting fan-shaped signals is thus possible, since the position of the emitter of the device emitting fan-shaped signals determines the spatial position of the fan. I.e. the position of the fan can be calculated from the position of the device. The position of the fan nevertheless determines the spatial position of the image data of the device. If one thus knows the relative position of the two imaging modalities in respect of each other, he/she also knows the relative position of the images generated thereby. The two imaging modalities are thus registered with one another after carrying out this method, since a mapping regulation can be determined, which connects and/or assigns to one another the two different coordinate systems of the two modalities and a superimposition and/or merging of the images generated thereby is easily possible. All additional changes of position can then be automatically detected by a computing device and included in a possible merging calculation.
The position determination of the fan of the device emitting fan-shaped signals in the 3D image data record can advantageously be performed automatically by a computing device, in particular by using at least one programming means. The automation of the position determination allows this to be performed in an extremely rapid and very precise fashion. The imaging unit in the 3D image data record is typically clearly silhouetted against the examined object and can thus be segmented with simple and rapidly operating algorithms. The position of the fan generated by this device can be inferred from the position of said device.
In the case of a 3D image-compatible device emitting fan-shaped signals, the center plane or a plane which is parallel to the center plane of the fan can preferably be used and the distance from the center plane can also be registered. The absolute position in the room is not important for the plane containing the fan, but instead its relative alignment compared with the imaging device outside the object. It is thus insignificant whether use is made of exactly the center plane or a plane which is parallel thereto; the line which is essentially perpendicular thereto and which connects the center point of the radiation source and the detector of the imaging device outside the object is always the same. Thus the plane which is most favorable for the plane calculations can be selected by the computing device.
Particularly advantageously, in the event of an interruption in the registration, the 3D image data record containing the device emitting fan-shaped signals can be recorded again, but with a smaller range which is essentially limited to the device. Such an interruption represents a movement for instance. This can be caused by the body of the patient moving or also merely by organ movements. In order to detect such an interruption in the registration, the device emitting fan-shaped signals can be equipped with a position detection device. Alternatively, two-dimensional x-ray images could also be recorded prior to and after the registration for this position detection and one possible displacement of the device could also be determined therefrom. The position of the device emitting the fan-shaped signals is approximately known after all from the already recorded 3D image data record which is unfortunately no longer completely suited to the registration process; said position can thus be used predominantly for the registration such that a smaller range is selected for imaging purposes. Doses can be reduced as a result and the acceptance by the patient on the one hand and the service life of the device on the other hand can thus be increased.
Further advantages, features and details of the invention result from the exemplary embodiments described below as well as with reference to the drawings, in which;
In the event of the patient moving and a registration no longer being provided as a result, the method can be repeated, with it being possible to restrict the volume recorded by the 3D image data record 7 to the ultrasound emitter 4. A reduction in the exposure to dose is achieved as a result. Such an interruption in the registration is determined by a position detection system. The recording of two-dimensional x-ray images prior to and after the registration lends itself to this for instance. The position of the ultrasound emitter and a possible movement between the recordings can be detected from this.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 005 118.7 | Jan 2008 | DE | national |
