Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-11-05
2001-07-24
Vo, Peter (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S425000, C600S427000, C600S429000, C607S002000, C607S006000, C607S009000, C607S115000, C607S116000, C601S001000
Reexamination Certificate
active
06266552
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a method and an arrangement for locating a measurement and/or a treatment catheter in a vessel or an organ of a patient, wherein signals are transmitted (emitted) by one of these catheters, the signals being used to locate the position of the catheter which transmitted the signals.
2. Description of the Prior Art
For many medical applications it is desirable to be able to locate a catheter in a patient, e.g. in angiographic examinations and in cardiac diagnostics and therapy.
Thus, U.S. Pat. No. 5,042,486 describes a method for real time portrayal of a catheter in a vessel, which makes use of a transmitter for electromagnetic or acoustic waves located at the tip of the catheter. These waves are received by receiving antennas attached to the exterior surface of the patient and are converted into electrical image signals. From these signals the position of the catheter relative to external antennas is determined. A disadvantage of this technique is that the patient may not flex or bend or even breathe since the external antennas will then move relative to each other and to the catheter and the information will be distorted and the results unreliable and inaccurate. In U.S. Pat. Nos. 5,391,199 and 5,443,489 apparatuses and methods for treating cardiac arrhythmias and for ablation are described. Reference catheters, having a receiving or sending antenna, are then introduced into the heart and the position of a mapping/ablating catheter relative the reference catheters is determined by use of an external transmitter or receiver. The primary image of the structure studied, e.g. the heart, upon which a catheter map is superimposed, is obtained by an appropriate method, such as by x-ray imaging. By using fixed catheters the accuracy of location is improved and the correct orientation and superposition of the vessel image and the catheter location map is facilitated. If three or more fixed reference catheters, introduced into the heart, are used, it is possible for the patient to move and breathe freely without impairing the results. It is thus possible to have the external antennas fixed relative to the room, and not necessary to have them fixed relative the patient. However, the use of external antennas for transmitting electromagnetic fields for this purpose is associated with difficulties when the patient is lying in a bed and if ultrasonic waves are used the patient should preferably be immersed in water to obtain a satisfactory signal transmission between the exterior and the interior of the patient. Thus, this technique is complicated and impractical.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a technique for locating a measurement and/or treatment catheter in a vessel or organ of a patient relative a fixed catheter, serving as a reference, with which technique the above discussed disadvantages of the prior art solutions are eliminated.
The above object is achieved in accordance with the principles of the present invention in a method and an arrangement for locating a measurement and/or a treatment catheter in a vessel or an organ of a patient, wherein a fixed catheter is positioned within the patient in the vicinity of a measurement and/or treatment catheter, with signals being transmitted from one of the catheters to the other, and wherein the transmitted signals are received by the other of the catheters and the position of the measurement and/or treatment catheter relative to the fixed catheter is determined from the received signals. Thus, in the present invention the signal transmission between the measurement and/or treatment catheter and the fixed catheter takes place entirely inside the patient. Thus, the problem related to transmission of signals between the exterior and the interior of the patient are eliminated and by positioning the fixed catheter in the vicinity of the measurement and/or treatment catheter these catheters are moving together and not relative to each other. The measurement results are consequently not affected by movement or breathing of the patient. Thus with the present invention the patient is allowed to move generally freely, an important advantage to the patient.
In an embodiment of the method according to the invention the signals are transmitted from two points, separated in the longitudinal direction of the catheter. In this way also the direction of the catheter can be determined.
According to another embodiment of the method according to the invention, wherein the transmitted signals are electromagnetic signals, the sign of the phase of the received signals are determined relative to the sign of the phase of the transmitted signals in order to determine the direction of the magnetic field uniquely. In this way it is possible to determine the direction of the measurement and/or treatment catheter tip relative to the direction of the induced magnetic field {overscore (B)} and accordingly to the direction of the fixed catheter.
According to still another embodiment of the method according to the invention the signals are formed of ultrasonic pulses, transmitted from one of the catheters and received at the other one and the position of the measurement and/or treatment catheter is determined from the flight times of the received pulses. In this way the results of the determination are independent of the amplitude of the received pulses. Further, the first signal received by the sensor in question will determine the shortest distance to the signal transmitting means and consequently reflections and scattering pose no problem.
According to another embodiment of the method according to the invention the ultrasonic pulses are transmitted from two points, separated in the longitudinal direction of one of the catheters and the pulses are received by sensors disposed on the other catheter in a triangular configuration, preferably positioned in the corners of an equilateral triangle, the transmitting points and the sensors being suitably positioned in different planes for improving the accuracy in the case of three sensors. In this way the position of the measurement and/or treatment catheter relative to the fixed catheter can be correctly determined. Of course more than three sensors can be used and the positions and number of the transmitting points and sensors can be interchanged. Theoretically it is not possible with this method, in the case of using only three sensors on the platform, to distinguish the true catheter position from its mirror positions. However, in practice this will be no problem and such a theoretical uncertainty in the obtained results can for example be eliminated by using sensors with a certain lobe directivity.
According to still another embodiment of the method according to the invention the distal tip of the measurement and/or treatment catheter is moved on a surface and the positions and directions of the tip are successively determined to map the surface. Thus, if electromagnetic signals are used the first measuring point will result in knowledge of the position and direction of the catheter tip of the measurement and/or treatment catheter relative to the fixed catheter. Since the position and direction of the fixed catheter are unknown this information does not provide much. However by moving the measurement and/or treatment catheter and repeating the measurement new positions relative to the fixed catheter are obtained which can be joined by surface elements. In this way e.g. the interior surface of a heart chamber can be mapped, including the direction of the measurement and/or treatment catheter tip, and shown as a three-dimensional image on a monitor, without knowing the starting positions of the catheters.
According to another embodiment of the method according to the invention a fluoroscopic biplane exposure or an ultrasound imaging of the catheters is performed at one stage to determine their positions relative the patient. Then it is possible to correctly orient the obtained topological map
Lin Jeoyuh
Schiff & Hardin & Waite
Siemens-Elema AB
Vo Peter
LandOfFree
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