Determining blood flow by measurement of temperature

• US 5,860,922 A
• Filed: 07/21/1997
• Issued: 01/19/1999
• Est. Priority Date: 09/07/1995
• Status: Expired due to Term

• Current Assignee: Naama Gordon
• Original Assignee: TECHNION RESEARCH AND DEVELOPMENT FOUNDATION, LTD.
• Inventors: Gordon, Naama, Sideman, Samuel, Beyar, Rafael
• Primary Examiner(s): Smith, Ruth S.
• Application Number:
  US08/897,423
• Time in Patent Office: 547 Days
• Field of Search: 600/431, 600/474, 600/481, 600/479, 600/504, 600/549, 73/861.05, 73/861.95
• US Class Current: 600/431
• CPC Class Codes: A61B 5/015 By temperature mapping of body part
• CPC Class Codes: A61B 5/026 Measuring blood flow A61B3/1233, A61B3/1241 take precedence
• CPC Class Codes: A61B 5/0275 using tracers, e.g. dye dilution

Abstract

A method for determining a flow rate of a substance or a thermo-contrast agent in an object including a surface and an upstream region, and the method comprising the steps of (a) providing the upstream region with a thermo-contrast agent; (b) obtaining successive temperature readings of at least a part of the surface of the object; (c) generating a temperature response curve from the temperature readings; (d) extracting a parameter from the temperature response curve; and (e) determining the flow rate from the parameter.

Claims

1. A method for determining a flow rate of a substance in an object, the object including a surface and an upstream region, comprising the steps of:

(a) providing the upstream region with a thermo-contrast agent;

(b) obtaining successive temperature readings of at least a part of the surface of the object;

(c) generating a temperature response curve from said temperature readings;

(d) extracting a parameter from said temperature response curve; and

(e) determining said flow rate from said parameter.

2. The method of claim 1, wherein said temperature readings are obtained by an approach selected from the group consisting of remote sensing and contact sensing.

3. The method of claim 2, wherein said remote sensing is effected by thermoimaging, whereas said contact sensing is effected by a contact thermosensor.

4. The method of claim 1, wherein said parameter is the area above said temperature response curve.

5. The method of claim 1, wherein said parameter is the peak temperature difference.

6. The method of claim 1, wherein said parameter is the slope of the descending part of said temperature curve.

7. The method of claim 1, wherein said parameter is the exponential recline coefficient of the ascending part of said temperature curve.

8. The method of claim 7, wherein said exponential recline coefficient is calculated by a non-linear parameter estimation.

9. The method of claim 8, wherein said determining of said flow is by said exponential recline coefficient according to a heat-transfer model.

10. The method of claim 1, wherein said parameter is selected from the group of parameters consisting of time to peak, time to half decline, time to half recline, appearance disappearance time, time from peak to half recline, time from half decline to half recline and parameter alpha from a gamma-variant function.

11. The method of claim 1, wherein said object is a body organ of a living creature.

12. The method of claim 11, wherein said body organ is selected from the group of body organs consisting of a heart and a coronary artery.

13. The method of claim 11, wherein said body organ is of a human.

14. The method of claim 13, wherein said body organ is selected from the group of body organs consisting of a heart and a coronary artery.

15. The method of claim 1, applied during an open or closed chest surgery.

16. The method of claim 1, wherein said object is a non-living object.

17. The method of claim 1, wherein said substance is blood.

18. The method of claim 1, wherein said thermo-contrast agent is cold relative to said substance.

19. The method of claim 1, wherein said thermo-contrast agent is hot relative to said substance.

20. The method of claim 1, wherein said substance is selected from the group of substances consisting of liquid substances, gas substances, solid substances and mixtures of liquid substances, gas substances and solid substances.

21. The method of claim 1, wherein said thermo-contrast agent is selected from the group of thermo-contrast agents consisting of liquid thermo-contrast agents, gas thermo-contrast agents, solid thermo-contrast agents and mixtures of liquid thermo-contrast agents, gas thermo-contrast agents and solid thermo-contrast agents.

22. A method for determining a flow rate of a thermo-contrast agent in an object, the object including a surface and an upstream region, comprising the steps of:

(a) providing the upstream region with the thermo-contrast agent;

(b) obtaining successive temperature readings of at least a part of the surface of the object;

(c) generating a temperature response curve from said temperature readings;

(d) extracting a parameter from said temperature response curve; and

(e) determining said flow rate from said parameter.

23. The method of claim 22, wherein said temperature readings are obtained by an approach selected from the group consisting of remote sensing and contact sensing.

24. The method of claim 23, wherein said remote sensing is effected by thermoimaging, whereas said contact sensing is effected by a contact thermosensor.

25. The method of claim 22, wherein said parameter is the area above said temperature response curve.

26. The method of claim 22, wherein said parameter is the peak temperature difference.

27. The method of claim 22, wherein said parameter is the slope of the descending part of said temperature curve.

28. The method of claim 22, wherein said parameter is the exponential recline coefficient of the ascending part of said temperature curve.

29. The method of claim 28, wherein said exponential recline coefficient is calculated by a non-linear parameter estimation.

30. The method of claim 29, wherein said determining of said flow is by said exponential recline coefficient according to a heat-transfer model.

31. The method of claim 22, wherein said parameter is selected from the group of parameters consisting of time to peak, time to half decline, time to half recline, appearance disappearance time, time from peak to half recline, time from half decline to half recline and parameter alpha from a gamma-variant function.

32. The method of claim 22, wherein said object is a body organ of a living creature.

33. The method of claim 32, wherein said body organ is selected from the group of body organs consisting of a heart and a coronary artery.

34. The method of claim 32, wherein said body organ is of a human.

35. The method of claim 34, wherein said body organ is selected from the group of body organs consisting of a heart and a coronary artery.

36. The method of claim 22, applied during an open or closed chest surgery.

37. The method of claim 22, wherein said object is a non-living object.

38. The method of claim 22, wherein said thermo-contrast agent is selected from the group of substances consisting of blood, saline, crystalloid cardioplegia and any combination of blood, saline and crystalloid cardioplegia.

39. The method of claim 22, wherein said thermo-contrast agent is cold relative to said object.

40. The method of claim 22, wherein said thermo-contrast agent is hot relative to said object.

41. The method of claim 22, wherein said thermo-contrast agent is selected from the group of thermo-contrast agents consisting of liquid thermo-contrast agents, gas thermo-contrast agents, solid thermo-contrast agents and mixtures of liquid thermo-contrast agents, gas thermo-contrast agents and solid thermo-contrast agents.