Volumetric physiological measuring system and method

• US 7,390,307 B2
• Filed: 09/25/2003
• Issued: 06/24/2008
• Est. Priority Date: 10/28/1999
• Status: Expired due to Fees

• Current Assignee: Volusense AS
• Original Assignee: Volusense AS
• Inventors: Eriksen, Erik, Eriksen, Morten
• Primary Examiner(s): Marmor, II; Charles A.
• Assistant Examiner(s): Natnithithadha; Navin
• Application Number:
  US10/671,011
• Publication Number:
  US 20040133117A1
• Time in Patent Office: 1,734 Days
• Field of Search: 600529-543, 600/300, 600/301, 600/481, 600/483, 600/527, 600/547, 600/587, 600/595, 738/610.8, 738/611.1, 738/611.2, 738/611.3, 738/611.5, 324/228, 324/262, 324/258
• US Class Current: 600/595
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• 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 5/062 using magnetic field
• CPC Class Codes: A61B 5/1073 Measuring volume, e.g. of limbs
• CPC Class Codes: A61B 5/1135 by monitoring thoracic expansion

Abstract

A system and method for measuring volumes and areas using electromagnetic induction techniques. A current is generated and fed into one of two coil assemblies to induce voltage into another coil assembly to provide accurate values for volume or area.

Claims

1. A device for measuring the movement of an object comprising:

a. first and second matched pairs of fixed coils;

b. a patient coil configured to wrap elastically around a patient'"'"'s body part;

c. a current source coupled to, and adapted to energize, either the matched pairs of fixed coils or the patient coil; and

d. a volume sensing element comprising whichever of the matched pairs of fixed coils or the patient coil that is not coupled to the current source;

e. whereby the first and second matched pairs of fixed coils are arranged to reduce a sum of magnetic noise signals from remote sources to zero and to generate a relatively homogeneous magnetic field in a spatial volume occupied by the patient'"'"'s body part.

2. The device of claim 1, wherein the spatial volume has a center and the first and second matched pairs of fixed coils are arranged symmetrically about a vertical plane extending through the center of the spatial volume and are arranged above a horizontal plane passing through the center of the spatial volume.

3. The device of claim 2, wherein the first matched pair of fixed coils are each positioned approximately 503 millimeters from the vertical plane.

4. The device of claim 3, wherein the second matched pair of fixed coils are each positioned approximately 650 millimeters from the vertical plane.

5. The device of claim 2, wherein the spatial volume has a bottom and wherein (a) the first matched pair of fixed coils each comprise approximately 300 turns, (b) the second matched pair of fixed coils each comprise approximately 90 turns, (c) the first matched pair of fixed coils are wound on a first pair of rods that are positioned approximately 420 millimeters above the bottom of the spatial volume, (d) the second matched pair of fixed coils are wound on a second pair of rods that are positioned approximately 510 millimeters above the bottom of the spatial volume, (e) the first matched pair of fixed coils are each positioned approximately 503 millimeters from the vertical plane, (f) the second matched pair of fixed coils are each positioned approximately 650 millimeters from the vertical plane, and (g) the spatial volume extends 250 millimeters in the vertical direction and 400 millimeters in the horizontal direction.

6. The device of claim 1, wherein the current source is coupled to, and adapted to energize, the matched pairs of fixed coils, and the volume sensing element comprises the patient coil.

7. The device of claim 1, wherein the current source is coupled to, and adapted to energize, the patient coil, and the volume sensing element comprises the matched pairs of fixed coils.

8. The device of claim 1, wherein the spatial volume extends 250 millimeters in the vertical direction and 400 millimeters in the horizontal direction.

9. The device of claim 1, wherein the first matched pair of fixed coils each comprise approximately 300 turns and the second matched pair of fixed coils each comprise approximately 90 turns.

10. The device of claim 1, wherein the spatial volume has a bottom and wherein the first matched pair of fixed coils are wound on a first pair of rods that are positioned approximately 420 millimeters above the bottom of the spatial volume.

11. The device of claim 10, wherein the second matched pair of fixed coils are wound on a second pair of rods that are positioned approximately 510 millimeters above the bottom of the spatial volume.

12. The device of claim 1, wherein the first and second matched pairs of fixed coils are wound on first and second pairs of ferrite rods, each rod having a diameter of approximately 8 millimeters, a length of approximately 150 millimeters, and a g value of approximately 100.

13. The device of claim 1, wherein the first matched pair of fixed coils comprise first and second fixed coils connected electrically in opposite phases, and the second matched pair of fixed coils comprise third and fourth fixed coils connected electrically in opposite phases.

14. The device of claim 1, wherein the device is configured to measure variations in tidal volumes in neonates less than 1000 grams.

15. The device of claim 1, wherein (i) the spatial volume has a center, (ii) first and second planes both extend through the center, the first plane being perpendicular to the second plane, and (iii) the first and second matched pairs of fixed coils are arranged symmetrically about the first plane and on the same side of the second plane.

16. A method of measuring the movement of an object comprising:

a. arranging first and second matched pairs of fixed coils;

b. wrapping a patient coil around a patient'"'"'s body part;

c. energizing either the matched pairs of fixed coils or the patient coil;

d. sensing a volume of the body part with whichever of the matched pairs of fixed coils or the patient coil is not energized;

e. reducing a sum of magnetic noise signals from remote sources to zero by the arrangement of the first and second matched pairs of fixed coils; and

f. generating a relatively homogeneous magnetic field in a spatial volume occupied by the patient'"'"'s body part.

17. The method of claim 16, wherein the spatial volume has a center and the first and second matched pairs of fixed coils are arranged symmetrically about a vertical plane extending through the center of the spatial volume and are arranged above a horizontal plane passing through the center of the spatial volume.

18. The method of claim 17, wherein the first matched pair of fixed coils are each positioned approximately 503 millimeters from the vertical plane.

19. The method of claim 18, wherein the second matched pair of fixed coils are each positioned approximately 650 millimeters from the vertical plane.

20. The method of claim 17, wherein the spatial volume has a bottom and wherein (a) the first matched pair of fixed coils each comprise approximately 300 turns, (b) the second matched pair of fixed coils each comprise approximately 90 turns, (c) the first matched pair of fixed coils are wound on a first pair of rods that are positioned approximately 420 millimeters above the bottom of the spatial volume, (d) the second matched pair of fixed coils are wound on a second pair of rods that are positioned approximately 510 millimeters above the bottom of the spatial volume, (e) the first matched pair of fixed coils are each positioned approximately 503 millimeters from the vertical plane, (f) the second matched pair of fixed coils are each positioned approximately 650 millimeters from the vertical plane, and (g) the spatial volume extends 250 millimeters in the vertical direction and 400 millimeters in the horizontal direction.

21. The method of claim 16, wherein energizing comprises energizing the matched pairs of fixed coils, and sensing comprises sensing with the patient coil.

22. The method of claim 16, wherein energizing comprises energizing the patient coil, and sensing comprises sensing with the matched pairs of fixed coils.

23. The method of claim 16, wherein the spatial volume extends 250 millimeters in the vertical direction and 400 millimeters in the horizontal direction.

24. The method of claim 16, wherein the first matched pair of fixed coils each comprise approximately 300 turns and the second matched pair of fixed coils each comprise approximately 90 turns.

25. The method of claim 16, wherein the spatial volume has a bottom and wherein the first matched pair of fixed coils are wound on a first pair of rods that are positioned approximately 420 millimeters above the bottom of the spatial volume.

26. The method of claim 25, wherein the second matched pair of fixed coils are wound on a second pair of rods that are positioned approximately 510 millimeters above the bottom of the spatial volume.

27. The method of claim 16, wherein the patient is a neonate less than 1000 grams.

28. The method of claim 16, wherein (i) the spatial volume has a center, (ii) first and second planes both extend through the center, the first plane being perpendicular to the second plane, and (iii) the first and second matched pairs of fixed coils are arranged symmetrically about the first plane and on the same side of the second plane.

29. The method of claim 16, wherein the first matched pair of fixed coils comprises first and second fixed coils connected electrically in opposite phases, and the second matched pair of fixed coils comprises third and fourth fixed coils connected electrically in opposite phases.