System for quantifying blood flow in tissue and updating tissue baseline conditions
First Claim
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1. Apparatus for determining the perfusion of blood in living tissue comprising:
- means in thermal contact with tissue in a capillary bed for sensing the reference temperature of the capillary bed when the capillary bed is unheated;
means in thermal contact with the capillary bed for heating the capillary bed;
means for applying power to said heating means sufficiently rapidly to raise the temperature of said heating means to a temperature above said reference temperature so that the power necessary to maintain said heating means temperature varies as a function of time;
means for determining the temperature difference between said heating means temperature and said reference temperature, means for determining the resistance of said heating means at said heating means temperature and means for determining the time varying relationship between the power required to maintain said heating means at said heating means temperature after said temperature has been reached and the time during which said power is being applied thereto;
a data processor responsive to said temperature difference, said heating means resistance and said time varying power and time relationship for determining a perfusion related value; and
means for evaluating conditions that affect the reference temperature of the capillary bed and recognizing conditions under which the reference temperature is no longer valid; and
means for providing an output in response to said evaluating and recognizing means.
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Abstract
Methods and apparatus for determining blood flow in tissue are disclosed. The methods and apparatus are used to establish a baseline for both thermal properties of the tissue and non-physiologic conditions. Periodic changes in either or both constituents of the baseline are determined and, when the changes correspond to a need for a new baseline, a new baseline is established.
33 Citations
19 Claims
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1. Apparatus for determining the perfusion of blood in living tissue comprising:
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means in thermal contact with tissue in a capillary bed for sensing the reference temperature of the capillary bed when the capillary bed is unheated; means in thermal contact with the capillary bed for heating the capillary bed; means for applying power to said heating means sufficiently rapidly to raise the temperature of said heating means to a temperature above said reference temperature so that the power necessary to maintain said heating means temperature varies as a function of time; means for determining the temperature difference between said heating means temperature and said reference temperature, means for determining the resistance of said heating means at said heating means temperature and means for determining the time varying relationship between the power required to maintain said heating means at said heating means temperature after said temperature has been reached and the time during which said power is being applied thereto; a data processor responsive to said temperature difference, said heating means resistance and said time varying power and time relationship for determining a perfusion related value; and means for evaluating conditions that affect the reference temperature of the capillary bed and recognizing conditions under which the reference temperature is no longer valid; and
means for providing an output in response to said evaluating and recognizing means. - View Dependent Claims (2, 3, 4, 5)
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6. Apparatus for determining the perfusion of blood in living tissue comprising:
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means adapted to contact tissue for sensing a reference temperature of the tissue when the tissue is unheated; a heating element for heating tissue including tissue contacted by said heating element, said heating element having a predetermined thermal conductivity and a predetermined thermal diffusivity; means for applying power to said heating element sufficiently rapidly to raise the temperature of said heating element above said reference temperature so that the power necessary to maintain said heating element temperature varies as a function of time; means for determining the temperature difference between said heating element temperature and said reference temperature, means for determining the resistance of said heating element at said heating element temperature and means for determining the time varying relationship between the power required to maintain said heating element at said temperature after said temperature has been reached and the time during which said power is being applied thereto; a data processor responsive to said temperature difference, said heating element resistance, said applied power in accordance with said time varying power and time relationship, said predetermined thermal conductivity and/or diffusivity of said heating element, and a change in said reference temperature for determining the thermal conductivity and/or the thermal diffusivity of the tissue; means for computing the perfusion of blood in the tissue as a function of the thermal conductivity and/or the thermal diffusivity of the tissue; and means for evaluating conditions that affect the reference temperature of the tissue and recognizing conditions under which the reference temperature is no longer valid; and
means for providing an output in response to said evaluating and recognizing means. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification