Method and apparatus for determining analyte concentration using phase and magnitude detection of a radiation transfer function

An apparatus for detecting a concentration of a substance in a body, the apparatus comprising:

• a thermal device adapted to induce a temperature differential at a surface of the body;
• a detector adapted to monitor radiation, including radiation emitted from the body surface;
• a controller coupled to drive the thermal device to vary the temperature at the surface according to a surface temperature modulation;
• and
• a signal processor connected with the detector and adapted to detect a phase and magnitude of a modulation of the emitted radiation, the signal processor including a transfer function, wherein the transfer function relates the surface temperature modulation to the modulation of the emitted radiation.

A method for determining an optical absorbance of a tissue comprising:

• determining a thermal transfer function that relates a temperature modulation at a surface of a body to a depth-dependant temperature modulation within the body;
• defining a radiation transfer function that relates a modulation of radiation emitted from the surface of the body to the depth-dependant temperature modulation the radiation transfer function including the absorbance;
• and
• determining a correlation between a phase or magnitude of the radiation transfer function and the absorbance.

An apparatus for detecting a concentration of a substance in a body of a patient, the apparatus comprising:

• a thermal device adapted to induce a temperature differential at a surface of the body;
• a detector adapted to monitor radiation, including radiation emitted from the body surface;
• a controller coupled to drive the thermal device to vary the temperature at the surface according to a surface temperature modulation;
• a signal processor connected with the detector and adapted to detect a phase and magnitude of a modulation of the emitted radiation;
• a memory, including a plurality of model transfer functions stored therein, the model transfer functions relating to a respective plurality of model responses between the surface temperature modulation and the modulation of the emitted radiation, wherein each model transfer function depends on a set of patient parameters;
• and
• a communication device adapted to connect the signal processor with the memory and to communicate a selected one of the model transfer functions to the signal processor, wherein the signal processor determines the concentration of the substance based on the phase and magnitude of the emitted radiation relative to the temperature modulation and the selected model transfer function.