Method for localizing a medical instrument introduced into the body of an examination object

• US 20070066889A1
• Filed: 09/21/2006
• Published: 03/22/2007
• Est. Priority Date: 09/21/2005
• Status: Active Grant

• Current Assignee: Siemens Healthcare GMBH (Siemens AG)
• Original Assignee: Siemens AG
• Inventors: Boese, Jan, Sandkamp, Bernhard
• Granted Patent: US 7,778,689 B2
• Time in Patent Office: Days
• US Class Current: 600/424
• CPC Class Codes: A61B 2034/2053 Tracking an applied voltage gradient
• CPC Class Codes: A61B 2562/17 Comprising radiolucent components
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/06 Devices, other than using radiation, for detecting or locating foreign bodies for removing same A61B17/50 ; determining position of probes within or on the body of the patient
• CPC Class Codes: A61B 5/063 using impedance measurements
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 6/12 Arrangements for detecting or locating foreign bodies

Abstract

A method for localizing a medical instrument, in particular a catheter or guide wire, introduced into the body of an examination object, comprising the steps: arrangement of at least four electrodes on the body of the examination object, recording of three-dimensional image data of a body region of the examination object that is of interest by means of an imaging medical examination device, determination of a model of the electrical conductivity of the examination object as a function of the recorded three-dimensional image data, determination of the electric field distribution when a voltage and/or current is/are applied for at least three different electrode pairs formed from the four electrodes as a function of the conductivity model and the spatial positions of the electrodes, not all the electrodes lying in one plane, application of a voltage and/or a current at each electrode pair and determination of a voltage value at an electrode of the medical instrument for the at least three electrode pairs and determination of the spatial position of the medical instrument as the point of intersection of the equipotential surfaces assigned to the at least three voltage values at the electrode of the medical instrument.

Claims

1-15. -15. (canceled)

16. A method for locating a medical instrument introduced into a body of an examination object, comprising:

arranging at least four electrodes at the body of the examination object;

recording a three-dimensional image data of a body region of the examination object by an imaging medical examination device;

determining an electrical conductivity model of the examination object as a function of the three-dimensional image data;

determining an electric field distribution of the examination object as a function of the electrical conductivity model and spatial positions of the electrodes if a voltage is applied for at least three different electrode pairs formed from the four electrodes which do not all lies in one plane;

applying the voltage at each of the three electrode pairs respectively;

determining three voltage values at an electrode of the medical instrument for the applied voltage at each of the three electrode pairs respectively; and

determining a spatial position of the medical instrument as a point of an intersection of equipotential surfaces assigned to the three voltage values at the electrode of the medical instrument.

17. The method as claimed in claim 16, wherein the electrical conductivity model is determined as a function of an assignment of an intensity value of the image data to a conductivity value.

18. The method as claimed in claim 16, wherein at least two different tissue types with differing conductivities are differentiated in the body of the examination object for determining the electrical conductivity model.

19. The method as claimed in claim 18, wherein the different tissue types are selected from the group consisting of:

bone tissue, organ tissue, air-equivalent tissue, and water-equivalent tissue.

20. The method as claimed in claim 16, wherein the three-dimensional image data is recorded by a method selected from a group consisting of:

a rotational angiography, a computer tomography, a magnetic resonance recording, and an ultrasound recording.

21. The method as claimed in claim 16, wherein different image recording methods are combined for recording the three-dimensional image data or for determining the spatial positions of the electrodes.

22. The method as claimed in claim 16, wherein the spatial positions of the electrodes are determined from the three-dimensional image data.

23. The method as claimed in claim 22, wherein X-ray transparent electrodes or electrodes with an X-ray absorbing marker are used when the image data is recorded using X-rays.

24. The method as claimed in claim 16, wherein the electrical conductivity model, or the spatial positions of the electrodes, or the equipotential surfaces, or the point of the intersection of equipotential surfaces is determined automatically or at least partially manually.

25. The method as claimed in claim 16, wherein the medical instrument and the spatial position of the medical instrument are displayed at a display unit.

26. The method as claimed in claim 16, wherein when more than three voltage values are determined at the electrode of the medical instrument, the spatial position of the medical instrument is determined by averaging the voltage values from the equipotential surfaces.

27. The method as claimed in claim 16, wherein the electrodes comprises skin electrodes and inside of the body electrodes.

28. The method as claimed in claim 27, wherein the skin electrodes are electrodes implementing an electrophysiological method and the inside of the body electrodes are electrodes of a fixed-position medical instrument inside of the body.

29. The method as claimed in claim 28, wherein the electrode pair is formed from one of the skin electrodes and one of the inside of the body electrodes

30. The method as claimed in claim 16, wherein at least one of the electrodes is arranged in an area of the image data recording.

31. The method as claimed in claim 16, wherein at least one of the electrodes is arranged outside an area of the image data recording and a voltage drop outside the area of the image data recording is determined by a calibrating method or by information of at least one other electrode pair.

32. The method as claimed in claim 31, wherein a medical instrument comprising more than one electrode is used for calibrating.

33. A method for locating a medical instrument introduced into a body of an examination object, comprising:

arranging at least four electrodes at the body of the examination object;

recording a three-dimensional image data of a body region of the examination object by an imaging medical examination device;

determining an electrical conductivity model of the examination object as a function of the three-dimensional image data;

determining an electric field distribution of the examination object as a function of the electrical conductivity model and spatial positions of the electrodes if a current is applied for at least three different electrode pairs formed from the four electrodes which do not all lies in one plane;

applying the current at each of the three electrode pairs respectively;

determining three voltage values at an electrode of the medical instrument for the applied current at each of the three electrode pairs respectively; and

determining a spatial position of the medical instrument as a point of an intersection of equipotential surfaces assigned to the three voltage values at the electrode of the medical instrument.

34. A device for locating a medical instrument introduced into a body of a patient, comprising:

a patient supporting table which supports a patient having at least four electrodes arranged at the body of the patient;

a unit connected with the electrodes which generates and detects signals of the electrodes;

a medical imaging device which records a three-dimensional image data of a body region of the patient; and

a processing device which;

determines an electrical conductivity model of the patient as a function of the three-dimensional image data,

determines an electric field distribution of the patient as a function of the electrical conductivity model and spatial positions of the electrodes if a voltage is applied for at least three different electrode pairs formed from the four electrodes which do not all lies in one plane,

determines three voltage values at an electrode of the medical instrument after applying the voltage at each of the three electrode pairs respectively, and

determines a spatial position of the medical instrument as a point of an intersection of equipotential surfaces assigned to the three voltage values at the electrode of the medical instrument.

35. The method as claimed in claim 34, wherein a current is applied for the three different electrode pairs.