SENSOR, APPARATUS AND METHOD FOR NON-INVASIVELY MONITORING BLOOD CHARACTERISTICS OF A SUBJECT

• US 20120209095A1
• Filed: 02/15/2011
• Published: 08/16/2012
• Est. Priority Date: 02/15/2011
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Huiku, Matti
• Granted Patent: US 8,694,067 B2
• Time in Patent Office: Days
• US Class Current: 600/322
• CPC Class Codes: A61B 5/14551 for measuring blood gases

Abstract

A sensor, apparatus and method for non-invasively monitoring blood characteristics of a subject are disclosed. The sensor comprises an emitter unit configured to emit radiation through the tissue of the subject at a plurality of measurement wavelengths and a detector unit that comprises photo detectors. To achieve a simple sensor assembly, the photo detectors are together adapted to receive the radiation at the plurality of wavelengths and to produce in-vivo measurement signals corresponding to the plurality of measurement wavelengths, the in-vivo measurement signals being indicative of absorption caused by blood of the subject. Furthermore, the photo detectors are mounted so that optical paths from the emitter unit to the photo detectors are different, and the plurality of wavelengths are divided between the photo detectors so that two spectrally adjacent photo detectors have at least one common wavelength. The apparatus comprises a path normalization unit configured to normalize the in-vivo measurement signals to an optical path specific to one of the photo detectors.

Claims

1. A sensor for determining blood characteristics of a subject, the sensor being attachable to the subject and comprising:

an emitter unit configured to emit radiation through the tissue of the subject at a plurality of measurement wavelengths; and

a detector unit comprising photo detectors that are together adapted to receive the radiation at the plurality of wavelengths and to produce in-vivo measurement signals corresponding to the plurality of measurement wavelengths, the in-vivo measurement signals being indicative of absorption caused by blood of the subject, wherein the photo detectors are mounted so that optical paths from the emitter unit to the photo detectors are different and wherein the plurality of wavelengths are divided between the photo detectors so that two spectrally adjacent photo detectors have at least one common wavelength.

2. The sensor according to claim 1, wherein the photo detectors are mounted side by side in the sensor.

3. The sensor according to claim 2, wherein the photo detectors are arranged in an array configuration.

4. The sensor according to claim 2, wherein the photo detectors are arranged in a matrix configuration.

5. The sensor according to claim 1, wherein the detector unit comprises two photo detectors having an overlapping spectral responsivity range from approximately 800 nm to approximately 1000 nm, and wherein the at least one common wavelength comprises one wavelength located within the overlapping spectral responsivity range.

6. The sensor according to claim 1, wherein the sensor comprises a silicon photodiode and an InGaAs photodiode.

7. The sensor according to claim 1, further comprising a path normalization unit configured to normalize the in-vivo measurement signals to an optical path specific to one of the photo detectors.

8. An apparatus for determining blood characteristics of a subject, the apparatus comprising:

an interface unit configured to receive in-vivo measurement signals from photo detectors, wherein the in-vivo measurement signals are indicative of absorption caused by blood of a subject and wherein each photo detector is adapted to receive optical signals from an optical path specific to the detector; and

a path normalization unit configured to normalize the in-vivo measurement signals to an optical path specific to one of the photo detectors.

9. The apparatus according to claim 8, wherein the path normalization unit is configured to

derive modulation signals from the in-vivo measurement signals, wherein each modulation signal represents a ratio of AC and DC signal components at a specific wavelength;

determine a ratio of two modulation signals obtained at a common wavelength respectively through two photo detectors;

select a set of modulation signals; and

multiply the selected modulation signals by the ratio.

10. The apparatus according to claim 8, further comprising a sensor unit attachable to the subject, the sensor unit comprising:

an emitter unit configured to emit radiation through the tissue of the subject at a plurality of measurement wavelengths; and

a detector unit comprising the photo detectors, wherein the photo detectors are together adapted to receive the radiation at the plurality of wavelengths and to produce the in-vivo measurement signals, wherein the photo detectors are mounted so that optical paths from the emitter unit to the photo detectors are different and wherein the plurality of wavelengths are divided between the photo detectors so that two spectrally adjacent photo detectors have at least one common wavelength.

11. A method for monitoring blood characteristics of a subject, the method comprising:

mounting multiple photo detectors in a sensor arrangement so that optical paths from an emitter unit to the photo detectors are different;

providing the emitter unit with a plurality of measurement wavelengths;

acquiring in-vivo measurement signals at the plurality of measurement wavelengths, the in-vivo measurement signals being indicative of absorption caused by blood of a subject;

determining a path normalization coefficient based on different in-vivo measurement signals obtained respectively from different photo detectors at a wavelength common to the different photo detectors;

applying the path normalization coefficient to selected in-vivo measurement signals, thereby to obtain path normalized in-vivo measurement signals; and

employing the path normalized in-vivo measurement signals for determining blood characteristics of the subject.

12. The method according to claim 11, wherein

the determining includes deriving in-vivo modulation signals from the in-vivo measurement signals, wherein each in-vivo modulation signal represents a ratio of AC and DC signal components at a specific wavelength;

the applying includes applying the path normalization coefficient to selected in-vivo modulation signals, thereby to obtain path normalized in-vivo modulation signals; and

the employing includes employing the path normalized in-vivo modulation signals for determining the blood characteristics.