Methods and apparatus for a remote, noninvasive technique to detect core body temperature in a subject via thermal imaging

Abstract

An approach to noninvasively, remotely and accurately detect core body temperature in a warm-blooded subject, human or animal, via thermal imaging. Preferred features such as the use of in-frame temperature references, specific anatomical target regions and a physiological heat transfer model help the present invention to overcome pitfalls inherent with existing thermal imaging techniques applied to physiological screening applications. This invention provides the ability to noninvasively, remotely and rapidly screen for diseases or conditions that are characterized by changes in core body temperature. One human application of this invention is the remote screening for severe acute respiratory syndrome (SARS), since fever is a common, early symptom. Other diseases and conditions that affect the core body temperature of humans or animals may also be noninvasively and remotely detected with this invention.

1 . A method of remotely and noninvasively determining a derived surface temperature of a distant subject, comprising the steps of:
 remotely and noninvasively acquiring thermal image data for a field of view that comprises at least a portion of a surface of the subject;   obtaining information from at least a first temperature reference surface having a first known temperature and a second temperature reference surface having a second known temperature, wherein the first and second known temperatures are different; and   deriving a calibrated surface temperature of the subject using the thermal image data corresponding to the surface and the first and second known reference temperatures, said calibrated surface temperature having an improved accuracy relative to the temperature indicated by the thermal image data corresponding to the surface.   
   
   
       2 . The method of  claim 1 , wherein at least one of the known reference temperatures is an ambient temperature near the subject surface. 
   
   
       3 . The method of  claim 1 , wherein said subject is selected from a human or an animal. 
   
   
       4 . The method of  claim 3 , wherein the surface is selected from an eye region, facial region, or a forehead region of the subject. 
   
   
       5 . The method of  claim 1 , wherein at least one of the first and second temperature references is an in-frame reference. 
   
   
       6 . The method of  claim 1 , wherein the first and second temperature references are in-frame temperature references. 
   
   
       7 . The method of  claim 1 , wherein the first temperature reference is at a temperature below an anticipated temperature of the subject surface, and the second temperature reference is at a temperature greater than the anticipated temperature of the subject surface. 
   
   
       8 . The method of  claim 7 , further comprising obtaining information from an ambient temperature reference near the subject surface. 
   
   
       9 . The method of  claim 1 , wherein the first temperature reference is at an ambient temperature near the subject. 
   
   
       10 . The method of  claim 1 , wherein the second temperature reference is at an ambient temperature near the subject. 
   
   
       11 . The method of  claim 1 , wherein the deriving step comprises the steps of using information comprising the reference temperatures to derive a calibration algorithm, and using the calibration algorithm to derive the calibrated surface temperature from information comprising the thermal image data corresponding to the surface. 
   
   
       12 . A method of remotely and noninvasively determining a core body temperature of a distant subject, comprising:
 remotely and noninvasively acquiring thermal image data for a field of view that comprises at least a portion of a surface of the subject;   acquiring an ambient temperature near said surface;   deriving the core body temperature of the subject using information comprising the ambient temperature and the thermal image data corresponding to the surface portion in a manner that accounts for a heat transfer impact of ambient temperature upon the surface temperature.   
   
   
       13 . The method of  claim 12 , wherein the ambient temperature is determined from the thermal image data. 
   
   
       14 . The method of  claim 12 , wherein the ambient temperature is acquired from an out of frame temperature reference. 
   
   
       15 . The method of  claim 12 , wherein said deriving step comprises calibrating the thermal image data and using the calibrated thermal image data to derive the core body temperature. 
   
   
       16 . The method of  claim 12 , wherein the surface is selected from an eye region, facial region, or a forehead region of the subject. 
   
   
       17 . A method of remotely and noninvasively determining a surface temperature of a distant subject, comprising the steps of:
 remotely and noninvasively acquiring thermal image data for a field of view that comprises at least a portion of a surface of the subject and at least two regions of differing emissivity;   deriving a calibrated surface temperature of the subject using information comprising the thermal image data of the subject surface portion and said two regions having differing emissivity, said calibrated surface temperature having an improved accuracy relative to the temperature indicated by the thermal image data corresponding to the surface.   
   
   
       18 . A method of remotely and noninvasively determining a core body temperature of a distant subject, comprising the steps of:
 remotely and noninvasively acquiring thermal image data for a field of view that comprises at least a portion of a surface of the subject;   deriving the core body temperature of the subject using information comprising an ambient temperature near said surface, humidity near said surface, and the thermal image data, said deriving occurring in a manner that accounts for a heat transfer impact of ambient temperature and humidity upon the surface portion of the subject.   
   
   
       19 . A thermal imaging system that derives a surface temperature of a distant subject from thermal image data, comprising
 a thermal imaging device that acquires thermal image data of at least a portion of a surface of the subject when the subject is within a field of view of the device;   first and second temperature references; and   program instructions that derive a calibrated surface temperature of the subject using information comprising the thermal image data corresponding to the surface and temperature information obtained from the first and second temperature references, said calibrated surface temperature having an improved accuracy relative to the temperature indicated by the thermal image data corresponding to the surface.