Non-invasive temperature measurement method and apparatus

• US 6,220,750 B1
• Filed: 03/29/1999
• Issued: 04/24/2001
• Est. Priority Date: 03/29/1999
• Status: Expired due to Fees

• Current Assignee: Yoram Palti
• Original Assignee: Yoram Palti
• Inventors: Palti, Yoram
• Primary Examiner(s): Bennett, G. Bradley
• Assistant Examiner(s): VERBITSKY, GAIL KAPLAN
• Application Number:
  US09/280,613
• Time in Patent Office: 757 Days
• Field of Search: 374/112, 374/164, 374/179, 374/208, 374/163, 374/166, 374/170, 374/174, 600/473, 600/474, 600/475
• US Class Current: 374/164
• CPC Class Codes: G01K 1/16 Special arrangements for conducting heat from the object to the sensitive element
• CPC Class Codes: G01K 1/165 for application in zero heat flux sensors
• CPC Class Codes: G01K 1/18 for reducing thermal inertia
• CPC Class Codes: G01K 7/02 using thermoelectric elements, e.g. thermocouples

Abstract

A method of measuring the temperature of the core of a body includes: a) providing a heat conductive space outside the body and in contact with its surface; b) monitoring the difference of the temperatures of two points located within the space and at different distances from the body surface; c) if the temperature difference indicates that heat is flowing from the body surface outwards, generating heat in the space in order to reduce the temperature difference; d) monitoring the temperature difference; and e) assuming the temperature of one of the two points, when the temperature difference is zero, as the temperature of body core.

Claims

1. A method of measuring the temperature of the core of a body, which comprises:

a) providing a heat conductive space outside the body and in contact with its surface;

b) monitoring the difference of the temperatures of two points located within said space and at different distances from said body surface;

c) if said temperature difference indicates that heat is flowing from the body surface outwards, generating heat in said space, to reduce said temperature difference;

d) monitoring said temperature difference; and

e) assuming the temperature of one of said two points, when said temperature difference is zero, as the temperature of said body core.

2. The method according to claim 1, further comprising continuing the generation of heat in said space until the difference of the temperatures of the two points located within said space has become zero, and then measuring the temperature of one of said two points.

3. The method according to claim 1, further comprising discontinuing the generation of heat in said space before the difference of the temperatures of the two points located within said space has become zero, extrapolating the curve expressing the variation of said temperature difference with time to calculate the zero time at which said temperature difference would have become zero, and extrapolating the curve expressing the variation of the temperature of one of said two points to calculate the temperature which it would have assumed at said calculated zero time.

4. The method according to claim 1, further comprising thermally insulating the heat conductive space on all its surfaces, except where it is intended to contact the surface of the body.

5. The method according to claim 1, wherein the body is a human body, and further comprising carrying out a calibration by applying the method to a typical human body.

6. An apparatus for measuring the temperature of the core of a body, which comprises:

I—

a capsule, the inside of which is heat conductive, which has a surface adapted to be placed in contact with the surface of the body the core temperature of which is to be measured, and which is thermally insulated on all its other surfaces;

II—

a heating element for heating the inside of the capsule;

III—

two temperature sensors for measuring the temperatures of two points inside the capsule or the difference of said temperatures;

IV—

a control module, including a power supply; and

V—

a connection between the capsule and the control module.

7. The apparatus according to claim 6, further comprising a temperature display.

8. The apparatus according to claim 6, wherein the temperature sensors are thermocouples.

9. The apparatus according to claim 6, wherein the inside of the capsule comprises a high heat conductivity and a low heat capacity.

10. The apparatus according to claim 8, wherein the control module comprises a power source for activating the heating element, a temperature measurement circuit connected to the thermocouples, a temperature display, and a controller receiving input from the thermocouple junctions and correspondingly controlling the activation of the heater.

11. The apparatus according to claim 10, wherein the temperature measurement circuit operates in two functional modes:

measuring the difference of the temperatures of two points inside the capsule, or measuring the temperature of one of said points.

12. The apparatus according to claim 6, wherein the two points are at different distances from the capsule surface adapted to be placed in contact with the surface of the body.

13. The apparatus according to claim 6, wherein the two points are located at or near a perpendicular to the capsule surface adapted to be placed in contact with the surface of the body.

14. The apparatus according to claim 6, for measuring the temperature of a human body.

15. The apparatus according to claim 13, wherein the surface of the capsule that is to be placed in contact with the surface of the body comprises adhesive so that it may be held firmly on the skin.

16. The apparatus according to claim 6, wherein the connection between the capsule and the control module comprises a first interface on the capsule and a second interface on the module and conductors for operatively connecting the interfaces when required.

17. The apparatus according to claim 6, wherein the capsule and control module are permanently connected.

18. The apparatus according to claim 17, wherein the capsule and control module form a unitary structure.

19. The apparatus according to claim 6, wherein the inside of the capsule comprises at least two metal sheets with high heat conductivity and low heat capacity, a filling of a heat conductive material between them, and metal bars connecting said metal sheets to spacer between them filled with air or a thermal insulator.

20. The apparatus according to claim 19, wherein the metal sheets are constructed of a metal selected from the group consisting aluminum and copper.

21. The apparatus according to claim 19, wherein the filling comprises air or a thermal insulator.

22. The apparatus according to claim 6, wherein the inside of the capsule comprises at least one conductive mesh.

23. The apparatus according to claim 6, further comprising a cold compensating junction.

24. The apparatus according to claim 6, further comprising means for attaching the capsule to the skin of a patient for as long as desired to obtain repetitive temperature readings.