Patent Application
20070282197
Exemplary embodiments of the invention are explained below in greater detail with reference to the drawings. The figures show:
In the figures the same elements or those with the same function have been labeled with the same reference symbols where it makes sense to do so.
The function of the catheter 1 is as follows:
The rotational movement of the magnet 4 creates a magnetic alternating field. The strength of the alternating field can be detected by means of sensors. As a result of the reduction of the strength of the alternating field as the distance from the magnet 4 increases, the strength of the alternating field contains information about the position of the magnet 4 relative to the sensor. This information can be used to determine the position of the magnet.
The strength of the alternating field able to be created at a predetermined distance from the magnet 4 increases as the rotation frequency increases. To determine the position of the magnet 4 in the body it is necessary for the alternating field to also be able to be detected with a suitable strength outside the body. The alternating field must be at least strong enough, despite absorption losses in the body, for a threshold value for the sensitivity of the sensor to still be exceeded outside the body. This can be achieved with the catheter 1 in a simple manner by the drive unit 10 being used with a sufficiently high speed of rotation. It can thus be insured that the position of the magnet 4, and thereby of the end section 3 of the catheter 1, is able to be determined with especially high accuracy.
The drive unit 10 can for example be an electric motor with a regulatable speed. To obtain a suitable speed, the drive unit 10 can also include a step-up or a reduction gear.
To transmit the rotational movement from the motor or gear to the shaft 5, the latter can be connected directly to a motor or gear shaft. It is also possible for a floating clutch, claw clutch, leaf clutch, disk clutch, magnetic clutch or suchlike to be used. The clutch can also include runner wheels or rollers which roll on a circumference of the shaft 5 and thus transmit the rotational movement to the shaft 5. The latter allow an especially simple connection of the shaft 5 to the motor or gear, especially for different types and diameters of shaft.
The turning movement is translated by means of the shaft 5 into the rotational movement 11. To avoid variations in the rotational movement 11, which influence the strength of the alternating field and are detrimental to the accuracy of the determination of the position of the magnet 4, the shaft 5 is guided in the tube 6. The inner surface of the tube 6 and the outer surface of the shaft are preferably embodied such that sliding friction between shaft 5 and tube 6 is especially small.
For a rigid catheter 1 the shaft 5 and the tube 6 can be embodied as rigid or flexible devices. For a flexible catheter the shaft 5 and the tube 6 are likewise flexible and are made of a sufficiently fracture-resistant, torsionally stiff, and kink-proof material. The shaft 5 and/or the tube 6 can for example be made of a plastic material.
The function of the OCT catheter 12 is as follows:
The alternating field is created in a similar way to field creation for the catheter 1 of
Unlike the catheter 1 of
Apart from this investigations by means of Optical Coherence Tomography (OCT) can be carried out using OCT catheter 12. To this end OCT catheter 12 can be introduced into a blood vessel for example. Subsequently light 16 is coupled in via the optical fiber 15. The light 16 exits in the end section 3 from the optical fiber 15 and hits the mirror 17 arranged on the attachment arm 13. The light 16 is deflected by the mirror 17 and exits through the exit window 18 from the catheter and hits the wall of the vessel. A reflection light reflected form the wall of the vessel in the direction of the mirror 17 can be directed via the mirror 17 and the optical fiber 15 to an OCT device not shown in the diagram for detection and processing of the reflection light. The fact that the mirror 17 is arranged on the attachment arm 13 means that the mirror 17 makes the same rotational movement 11 as the magnet 4. As a result of the rotational movement 1 the inside of the vessel wall can be scanned using the light 16. Based on the reflection light an OCT image of the vessel wall can be created which can be used for diagnostic purposes.
The advantage of the inventive OCT catheter 12, as well as giving the option of an especially precise location of the magnet 4, is that only one drive unit 10 is necessary for the magnet 4 and the mirror 17.
The function of the IVUS catheter 19 is as follows:
The inventive IVUS catheter 19 differs from the catheter 1 of
It is of course also possible to provide a drive unit in the end section with catheter 1 and OCT catheter 12.
With IVUS catheter 19 the transmission of the turning movement via the shaft 5 routed to the second end 7 in the tube 6 is omitted. This makes it possible to avoid the accuracy of the rotation frequency of the magnet 4 being adversely affected by friction resistance of the shaft 5 in the tube 6 and a lengthwise kinking of the IVUS catheter 19. As a result the position of the magnet 4 can be determined precisely.
The ultrasound converter 23 for carrying out intravascular ultrasound investigations is rotated together with the magnet 4.
The first line 24 is provided to supply the drive unit and/or of the ultrasound converter 23 with energy. The first line 24 can also be used for transmission of ultrasound signals from or to the ultrasound converter 23. Signals of the ultrasound converter can also be transmitted via a wireless connection, e.g. a radio connection. For energy supply a source of energy, such as an accumulator, can also be provided in the end section 3.
The motor can for example be an electric motor, stepping motor or a piezoelectric motor etc. The motor 21 can be selected in accordance with the torque for the magnet 4 and ultrasound converter 23 and the dimensions in the end section 3.
The inventive IVUS catheter 19 does not require any connections to external drive elements. As a result the handling of the IVUS catheter 19 can be greatly simplified. Like catheter 1 and OCT catheter 12, IVUS catheter 19 allows an especially simple and exact determination of the position of the magnet 4.
The function of the imaging position fixing system is as follows:
First of all image data is recorded by the x-ray device, which includes the x-ray source 26 and the detector 27, to create a first image of a section of the inside of the body 30. The image data can for example involve a series of 2D images. Such 2D image datasets allow a reconstruction of a 3D image of the recorded section. The image data detected by the detector 27 is transmitted via the second line 33 to an image creation device included in the computer 35. From the image data the image creation device can create a first image of the section, e.g. a 2D sectional image or 3D image. The image data recorded for creating each pixel of the first image is correlated with a first coordinate system which is defined by the image recording device. The image data also contains information about the markings 29. The position of the markings 29 can be identified and described with marking coordinates in the first coordinate system. By means of the image recording device the first image with the position of the markings 29 indicated within it can be displayed on a screen not shown in the diagram.
The first image can be used to create an overlay image, which reproduces the section of the inside of the body 30 and within this an exact position of the magnet 4.
To determine the position of the magnet 4, and thereby of the section 3, a magnetic alternating field is created by a rotation of the magnet 4. The magnet 4 can be rotated in a manner similar to the way in which it is rotated in the catheter 1, OCT catheter 12 and IVUS catheter 19 of
To create the overlay image it is necessary for the first and second coordinate system to be correlated. For correlation coordinates can additionally be determined in the second coordinate system for the magnet 4 positioned at the marking 29. The marking coordinates and the correlation coordinates describe the same point in space in the first or second coordinate system. Starting from this point a coordinate transformation rule between the first and second coordinate system can be determined, which represents a correlation of the first coordinate system and second coordinate system.
After correlation has been undertaken, the medical instrument, preferably a catheter, a needle and such like, is introduced into the section of the body 30. The position of the magnet 4 can be continuously determined by means of the magnetic field detection device and the position determination device. Provided the orientation of the section relative to the markings 29 does not change significantly, the same first image can be used for the overlay image and within this the instantaneous position of the magnet 4 can be shown. No continuous recording of image data is necessary, so that the applied x-ray dose can be drastically reduced.
An ongoing determination of the position of the magnet 4 can be undertaken as follows:
To determine the position of the magnet 4 location and time-dependent gradients of the alternating field can be dimensioned by means of the first 31 and second sensor 32 and by the further sensors not shown. The position of the magnet 4 can be computed on the basis of the sensor signals. To this end predetermined algorithms can be used, with which for example faults caused by electrical conductors, ferromagnetic objects and such like can also be taken into account.
The overall image can specify the position of the magnet 4 in the form of a simple symbol, e.g. a cross, an arrow and such like. It is also possible for the overlay image to contain a representation of the progress of the medical instrument in the body 30, with end section reproducing the position of the magnet 4. The presentation can for example involve a line which is clearly distinguishable from the first image in color tone.
The computer 35 can be used in the position fixing system for any given control, computation processes and such like. For example the computer 35 can control the actuators, the image recording device and such like and store, edit and process data determined by the first 31 and second sensor 32 and further sensors not shown, as well as the image data.
The x-ray device concerned can be an x-ray computer tomography device or x-ray C-arm device. A magnetic resonance tomography device, ultrasound tomography device, Positron Emission Tomography device, Single-Photon Emission Computer Tomography device or any other imaging device with which imaging data can be recorded for three-dimensional reconstruction of a section of the inside of the body 30 can be used to record image data.
The medical instrument 25 involved can be a catheter, especially an IVUS or OCT catheter, a needle, especially a puncturing needle or biopsy needle, a probe, especially a stomach or bowel probe.
The exemplary embodiments concerned are typical embodiments of the invention. Naturally alternate, similar embodiments are also conceivable within the framework of the invention. For example components of the embodiment can be replaced by alternate components which operate in the same way.
The inventive instrument, position fixing system and position fixing method make it possible to precisely fix the position of a magnet 4 provided in an end section 3. Furthermore the inventive magnet 4 attached to a rotation drive can be integrated in a simple manner into known, especially medical, devices. This applies especially to catheters with a shaft 5 which is present in any event. This allows an especially simple option for fixing the position of the magnet 4 or end section 3 to be provided. Apart from this it is possible, with recording systems in which the body is subjected to damaging radiation when the image data is recorded, to greatly reduce the radiation load.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 023 733.1 | May 2006 | DE | national |
