Method and arrangement for determining the location of a catheter within an animal body

• US 6,230,042 B1
• Filed: 02/25/1999
• Issued: 05/08/2001
• Est. Priority Date: 03/25/1998
• Status: Expired due to Term

• Current Assignee: Siemens Healthcare GMBH (Siemens AG)
• Original Assignee: Siemens-Elema AB (Siemens AG)
• Inventors: Slettenmark, Bruno
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US09/257,255
• Time in Patent Office: 803 Days
• Field of Search: 600/524
• US Class Current: 600/424
• 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

Abstract

A catheter arrangement has an active catheter, positionable in a vessel or organ of an animal, having at least one transducer disposed proximal the catheter tip; and a fixed catheter, also positionable within the animal in the vicinity of the active catheter, carrying a number of reference transducers. A signal processing unit is arranged to selectively operate the transducers to send and receive signals between the active and fixed catheters. The signal processing unit operates to calculate from the received signals at least two independent locations of the active catheter relative to the fixed catheter and to combine the independently calculated locations to provide a weighted average determination of the location in which the relative contributions of the calculated locations to the determined location decrease as their associated error values increase.

Claims

1. A method for determining a location of a catheter in an animal body, comprising the steps of:

providing a plurality of reference cites in a body;

measuring a distance between a catheter and said plurality of reference cites, thereby obtaining a plurality of measured distances;

making at least two independent calculations of a location of said catheter from said measured distances using triangulation;

associating respective error values with said at least two independent calculations;

assigning respective weighting values to said at least two independent calculations, said respective weighting values varying inversely relative to the respective error values, and thereby obtaining a plurality of weighted calculations; and

determining the location of said catheter by combining said plurality of weighted calculations.

2. A method as claimed in claim 1 wherein the step of assigning respective weighting values to said at least two independent calculations comprises measuring an absolute magnitude of a positional error in an independent calculation and assigning said weighting value dependent on said absolute magnitude of said positional error.

3. A method as claimed in claim 1 wherein the step of assigning respective weighting values to said at least two independent calculations comprises determining an angle of convergence on said catheter of straight lines proceeding between said catheter and respective reference cites used in said triangulation, and assigning the weighting value to an independent calculation dependent on said angle.

4. A method as claimed in claim 3 comprising determining an average measured distance of the respective distances between said catheter and said reference cites used in said triangulation, and assigning said weighting value dependent on said average.

5. A method as claimed in claim 1 wherein the step of combining said weighted calculations comprises for a plurality of weighted calculations greater than one, discarding said weighted calculation if the error value associated therewith exceeds a predetermined value.

6. A method for determining a position of a catheter tip within an animal body, comprising the steps of:

introducing into an animal body a catheter having a catheter tip and carrying at least one transducer disposed proximate said catheter tip;

disposing a plurality of spaced-apart reference transducers within said animal body;

transmitting respective signals between said at least one transducer and each of said reference transducers and measuring respective distances traveled by said respective signals between said at least one transducer and each of said reference transducers, thereby obtaining a plurality of measured distances;

making at least two independent calculations of a location of said catheter from said measured distances using triangulation;

assigning an error value to each of said at least two independent calculations;

assigning a weighting value to each of said at least two independent calculations, said weighting value varying inversely relative to said error value for the independent calculation associated therewith, thereby obtaining a plurality of weighted calculations; and

determining a location of said catheter by combining said plurality of weighted calculations.

7. A catheter arrangement comprising:

an active catheter adapted for implantation in an animal body, said active catheter having a catheter tip and carrying at least one transducer disposed proximate said catheter tip;

a fixed catheter adapted for implantation in an animal body carrying a plurality of reference transducers;

a signal processing unit including means for selectively operating said at least one transducer and said plurality of reference transducers to transmit and receive signals between said at least one transducer and said plurality of reference transducers, thereby obtaining a plurality of received signals;

said signal processing unit including means for calculating, from said received signals, at least two independently calculated locations of said active catheter relative to said fixed catheter; and

said signal processing unit including means for assigning respective error values to said at least two independently calculated locations and for combining said at least two independently calculated locations to produce a weighted average determination of the location of said active catheter to which each of said at least two independently calculated locations contribute inversely relative to their respective error values.

8. An arrangement as claimed in claim 7 wherein said signal processing unit comprises means for assigning a weighted value to each of said independently calculated locations dependent on the respective error value associated therewith, to obtain a plurality of weighted calculations, and means for combining said weighted calculations dependent on their respective weighted values to produce said weighted average.