Patent Application
20090234224
The present invention relates to a positioning device configured to be arranged to a target area inside a body. The invention also relates to a system for detecting a position of such a device.
In the published Swedish patent SE 511 291 is a method disclosed for administrating treatment radiation towards a target area, such as a tumour, within a patient. The administration direction is determined by providing a reference object which is inserted into the body of the patient close to the target area. The reference object has reference markings that may be detected using computed tomography (CT) or X-ray.
A drawback with the prior art is that an amount of radiation has to be used to detect the position of the reference object. The patient is submitted to an unnecessary exposure of radiation before the actual treatment may commence.
A solution to this drawback is directed to the use of magnetically activated sensors, or markers. These may be wirelessly implanted into a body and the markers could be tracked using an induced magnetic field. The sensors are normally permanently inserted into the body, and may migrate over time.
A drawback with this solution is that Magnetic Resonance Imaging (MRI) may not be used unless the sensors are removed.
Another solution is to provide a marker with an electromagnetic transmitter at the tip of the device that is inserted into the body and a receiver unit is placed outside the body to track the movement of the tip during the inserting procedure.
This solution has a drawback in that it experience a limited resolution, which leads to that x-ray normally still needs to be used to verify the position of the sensor/marker.
An object with the invention is to provide a device which may be used in a system to detect the position of the device which overcomes the above mentioned drawbacks.
The object is achieved in a device configured to be arranged in relation to a target area within a body. The device comprises at least one transmitter configured to emit an electromagnetic signal, which signal is received in at least three positions by a receiver arranged outside the body. The electromagnetic signal is generated in an externally arranged control unit and the device is configured to be connected to the control unit through transmission lines. The frequency of the emitted electromagnetic signal must be selected in such a way that a distance from each transmitter to each of the receiver's positions is within the same integer number of wavelengths of the electromagnetic signal.
The object is also achieved by a system using a device as described above.
An advantage with the present invention is that x-ray is not needed to be used to verify the position of the device.
Another advantage is that the present invention can be used to locate the device at all times after the device has been inserted into a body, which makes it possible to verify its position inside the body during e.g. treatment or feeding.
Still another advantage with the present invention is that there is a possibility for automation, i.e. radiation treatment can be administered automatically.
Still another advantage with the present invention is that the need for picture estimation by a doctor is eliminated, due to auto-positioning of the device.
An advantage with a preferred embodiment is that MRI may be used on the body since the positioning device easily may be removed from the body without the need for a surgical procedure.
This type of positioning device is preferably used during cancer treatment, such as prostate cancer, breast cancer uterus cancer, and a very accurate position of the prostate 17 (target area) is required to optimise the treatment procedure. The catheter is in this example inserted through a natural opening, as illustrated in
An electromagnetic signal is generated in the control unit 15 and is thereafter transmitted from the transmitter 11. The electromagnetic signal is adapted to propagate with a wavelength in the body and, in a first example, a phase difference of the electromagnetic signal is detected in at least three positions 18, preferably four or more positions, by a receiver 19 arranged outside the body. The wavelength is selected so that a distance from the transmitter 11 to each of said at least three positions 18 is within the same integer number of wavelengths of the electromagnetic signal. The distance between each transmitter and the positions 18 of the receiver 19 is preferably selected so that they operate in a near field region. A prior art detector system is described in an international patent application PCT/SE05/000646, assigned to the same applicant, wherein a transmitter arranged in relation to a target area inside a body transmits a signal having a frequency within the range of 5-350 MHz and a phase difference from the transmitted signal is detected by a receiver at three, or more, positions to track variations in position of the transmitter.
The prior art system described defines a transmitter and a multiple of receiving antennas that operates in a near field region. The behaviour of an electromagnetic signal in the near field region is known for a skilled person and is described in a publication with the title “Near field Phase Behavior”, by Hans Gregory Schantz, IEEE APS Conference July 2005. In this publication the author presents a reprint of a plot published in “Electric waves”, by Heinrich Hertz, London, Macmillian & Co. 1893, page 152 and a plot, shown in
The plot describes the phase behaviour of the magnetic field (H-field) and the electrostatic filed (E-field) below one wavelength of an electromagnetic signal. In this near field region of an antenna, the magnetic field and electrostatic field phases radically diverge, and in a far field region, many wavelengths away from a transmit antenna, the magnetic and electrostatic field move with perfect synchronized phase.
The separation of the magnetic field and the electrostatic field in the near field region opens up a number of possibilities to construct improved measurement systems. The shape of the wave front of the electromagnetic signal may be used to determine the distance between the transmitter and the receiver. It is also advantageous to increase the sensitivity of the measurement system by introducing electrostatically shielded antennas, which is possible since the magnetic field and electrostatic field are separated in the near field region, whereby the magnetic field is used to determine the variations of the position of the transmitter.
A more detailed description of the detector system may be found in the international patent application with the application number PCT/SE05/000646, which is hereby incorporated by reference.
In a second example, amplitude difference of the electromagnetic signal is detected instead of the phase difference as described above. A transmitter arranged in relation to a target area inside a body transmits a signal having a frequency within the range of 1 kHz-350 MHz and an amplitude difference from the transmitted signal is detected by a receiver at three, or more, positions to track variations in position of the transmitter. The amplitude of the magnetic field is preferably measured when operating in near field, for instance by measuring absolute value or mean value of the magnetic field.
It is of course possible to combine the above described examples and use both phase and amplitude difference to determine variations of the position of the transmitter.
The receiver 19, comprising a multiple of antennas at separate positions 18 (in this example four positions), is positioned on the outside of the body and is also connected to the control unit 15, and a very accurate tracking of the transmitter 11, and thus the prostate 17, may be performed. When radiotherapy treatment is completed, the removable catheter 10 is removed by deflating the expandable portion 13 and withdrawing the catheter 10.
The plaster could, for instance, be used when a patient having breast cancer is exposed to radiotherapy treatment. The plaster 20 is then attached to the breast in such a way that a relative distance between a target area in the breast and each transmitter 21 and 22 is established. The breathing of the patient, and thus the movement of the breast due to breathing, can be tracked, and the radiotherapy treatment can now be controlled more accurately by adapting the exposure dose to the position of the target area. It is of course possible to have only one transmitter, or even have more than two transmitters, without deviating from the scope of the invention as defined in the claims.
When the feeding tube has been placed in the right position, the insert 31 is withdrawn from the feeding tube 30 as illustrated by the arrow 34 in
In an alternative embodiment, the transmitter 32 and the transmission line 33 are integrated into a wall 37 of the feeding tube 30, which has the advantage that a removable insert is not necessary. The position of a hollow position secured device, such as a feeding tube, can continuously be monitored to track the position of the feeding tube 30 during feeding.
A wire-based implant covered with biocompatible material, i.e. without the need of a protective catheter, is also conceivable.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0502273-6 | Oct 2005 | SE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/SE2006/001135 | 10/5/2006 | WO | 00 | 4/11/2008 |
