Method and apparatus for measuring internal body temperature utilizing infrared emissions

• US 4,790,324 A
• Filed: 03/25/1987
• Issued: 12/13/1988
• Est. Priority Date: 10/23/1984
• Status: Expired due to Term

• Current Assignee: Sherwood Services AG
• Original Assignee: Intelligent Medical Systems, Inc. (Pfizer Inc.)
• Inventors: Phillips, David B., O'Hara, Gary J.
• Primary Examiner(s): Smith, Ruth S.
• Application Number:
  US07/031,164
• Time in Patent Office: 629 Days
• Field of Search: 128/664, 128/736, 374/121, 374/126, 374/129, 374/158, 374/2, 374/164, 374/170
• US Class Current: 600/474
• CPC Class Codes: G01J 2005/528 Periodic comparison
• CPC Class Codes: G01J 5/02 Constructional details
• CPC Class Codes: G01J 5/026 Control of working procedures of a pyrometer, other than calibration; Bandwidth calculation; Gain control
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/049 Casings for tympanic thermometers
• CPC Class Codes: G01J 5/05 Means for preventing contamination of the components of the optical system; Means for preventing obstruction of the radiation path
• CPC Class Codes: G01J 5/061 by controlling the temperature of the apparatus or parts thereof, e.g. using cooling means or thermostats
• CPC Class Codes: G01J 5/064 Ambient temperature sensor; Housing temperature sensor; Constructional details thereof
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0803 Arrangements for time-dependent attenuation of radiation signals
• CPC Class Codes: G01J 5/0805 Means for chopping radiation
• CPC Class Codes: G01J 5/0818 Waveguides
• CPC Class Codes: G01J 5/16 Arrangements with respect to the cold junction; Compensating influence of ambient temperature or other variables
• CPC Class Codes: G01J 5/52 using comparison with reference sources, e.g. disappearing-filament pyrometer

Abstract

A hand held probe unit has an infrared sensitive thermopile mounted in a metal housing kept at a constant reference temperature by a regulator circuit. A waveguide tube, surrounded by a thermally insulative probe, directs infrared emissions to the thermopile. The thermopile and regulator circuit of the probe unit are electrically connected to processing circuitry in a chopper unit. Prior to taking a patient'"'"'s temperature, the probe unit is mated with the chopper unit so that the thermopile detects infrared emissions from a reference target which is also kept at a constant reference temperature by another regulator circuit. The processing circuitry repeatedly acquires the output level of the thermopile and stores calibration data. The probe unit is then removed from the chopper unit, the probe is covered with an IR transparent, disposable speculum, and is inserted in the patient'"'"'s external ear canal. The processing circuitry then determines the patient'"'"'s core temperature by comparing the stored calibration data to the maximum output of the thermopile during a succession of ear canal samplings.

Claims

1. A method of measuring body temperature comprising the steps of:

preheating a probe assembly to a predetermined ear canal reference temperature, the probe assembly including an infrared level sensing device;

calibrating an output signal of the infrared level sensing device to a predetermined substantially constant target reference temperature;

inserting a portion of the preheated probe assembly into an ear canal of a patient;

directing infrared radiation emitted in the ear canal to the infrared level sensing device;

acquiring the output signal of the infrared sensing device;

processing the output signal to determine an internal body temperature; and

providing an indication of the internal body temperature to a user.

2. A method according to claim 1 wherein the calibrating step is accomplished by placing the probe assembly portion adjacent a target heated to the predetermined target reference temperature and repeatedly acquiring and storing the output signal of the infrared sensing device.

3. A method according to claim 2 wherein the output signal of the infrared sensing device is repeatedly acquired and stored when the probe assembly portion is inserted in the ear canal.

4. A method according to claim 3 wherein the processing step is accomplished by comparing a most recent output signal stored when the probe assembly portion was adjacent the target to a maximum output signal stored when the probe assembly portion was inserted in the ear canal.

5. A method according to claim 4 wherein the comparing step is performed within a predetermined maximum time interval between the removal of the probe assembly portion from the target and the insertion of the probe assembly portion in the ear canal to avoid an unacceptable level of drift.

6. An apparatus for measuring the internal temperature of a patient'"'"'s body comprising:

means for sensing the level of infrared radiation emitted in an ear canal of the patient and for producing an output signal representative of the sensed level, said sensing means comprising an infrared radiation sensor and means for directing infrared radiation emitted in the ear canal to the infrared radiation sensor;

means located outside the ear canal for thermostatically maintaining the environment of the infrared radiation sensor at a predetermined substantially constant reference temperature;

means for determining the internal body temperature based upon the output signal of the sensing means; and

means for calibrating the determining means.

7. In combination,

an infrared sensor;

a housing supporting and thermally connected to the infrared sensor, the housing including a metal body having a recess in which the infrared sensor is received;

means mounted in the metal body for heating the metal body upon application of first electrical signals thereto;

a hollow probe dimensioned and configured for insertion into the external ear canal and being made of a non-metallic material for minimizing conductive heat transfer when in contact with the skin of the ear canal;

a waveguide thermally coupled to the housing for directing infrared emissions to the sensor, the waveguide being dimensioned to extend within the probe; and

means for supporting the waveguide within the probe and spaced therefrom for directing infrared radiation from the ear canal to the infrared sensor.

8. The combination of claim 7 wherein the waveguide includes a cylindrical metal tube.

9. The combination of claim 8 wherein the probe includes a plastic tubular portion concentrically positioned relative to the metal tube of the waveguide.

10. The combination of claim 8 wherein the waveguide further includes a layer of gold covering an interior wall of the metal tube.

11. The combination of claim 7 and further comprising means mounted in the metal body for generating second signals representative of the temperature of the metal body.

12. The combination of claim 7 and further comprising a quantity of thermal grease packed between the sensor and a wall portion of the metal body defining the recess.

13. The combination of claim 7 and further comprising a speculum removably mounted over a tip of the probe and including a film membrane substantially transparent to infrared radiation and extending across, and spaced from, an end of the waveguide remote from the housing, the speculum being dimensioned and configured for partial insertion into the ear canal.