Method and apparatus to compensate for melanin and hemoglobin variation in determination of a measure of a glycation end-product or disease state using tissue fluorescence
First Claim
1. A method of determining a tissue state of the tissue of an individual, comprising:
- (a) illuminating a portion of the skin of the individual with excitation light in two or more illumination events which together span, in time, a plurality of heart beats of the individual, and determining the duration of each illumination event, the number of illumination events, or a combination thereof, responsive to a characteristic of the skin;
(b) detecting light emitted from the tissue by fluorescence of a chemical within the tissue responsive to the illumination events;
(c) determining the tissue state from the detected light and a model relating fluorescence and a tissue state.
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Abstract
A method of determining a measure of a tissue state (e.g., glycation end-product or disease state) in an individual is disclosed. A portion of the skin of the individual is illuminated with excitation light, then light emitted by the tissue due to fluorescence of a chemical with the tissue responsive to the excitation light is detected. The detected light can be combined with a model relating fluorescence with a measure of tissue state to determine a tissue state. The invention can illuminate the skin and detect responsive light over a time that spans a plurality of cardiac cycles of the individual, which can, as an example, help mitigate the effects of time-varying signals such as those due to hemoglobin. The invention can also determine the amount of light to be directed to the skin, for example by controlling the time that a light source is energized. The amount of illumination light can be determined from a skin reflectance characteristic such as pigmentation or melanin in the skin. Controlling the amount of light directed to the tissue can reduce the dynamic range required of a corresponding optical system, for example by allowing a single system to accurately measure individuals with very light skin and individuals with very dark skin.
14 Citations
25 Claims
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1. A method of determining a tissue state of the tissue of an individual, comprising:
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(a) illuminating a portion of the skin of the individual with excitation light in two or more illumination events which together span, in time, a plurality of heart beats of the individual, and determining the duration of each illumination event, the number of illumination events, or a combination thereof, responsive to a characteristic of the skin; (b) detecting light emitted from the tissue by fluorescence of a chemical within the tissue responsive to the illumination events; (c) determining the tissue state from the detected light and a model relating fluorescence and a tissue state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of determining a tissue state of the tissue of an individual, comprising:
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(a) determining a skin reflectance characteristic; (b) illuminating a portion of the skin of the individual with excitation light in two or more illumination events wherein the total excitation light energy is determined from the skin reflectance characteristic, and wherein the illumination events span a plurality of heart beats of the individual regardless of the skin reflectance characteristics; (c) detecting light emitted from the tissue by fluorescence of a chemical within the tissue responsive to the excitation light; (d) determining the tissue state from the detected light, either the skin reflectance characteristic or the excitation light, and a model relating fluorescence and a tissue state. - View Dependent Claims (22, 23, 24, 25)
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Specification