Method and device for optical measurement of biological properties
Inventors
Sarussi, Israel • Ben-Yishai, Arik • May, Johanan
Assignees
Publication Number
US-10537270-B2
Publication Date
2020-01-21
Expiration Date
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Abstract
The subject matter discloses a device for measuring biological properties of an examined tissue, the device comprising at least one light source configured and operable to illuminate the examined tissue with light radiation of one or more wavelengths at a certain light illumination direction; and a light detector located at a same side of said examined tissue and configured and operable to receive light components of said one or more wavelengths reflected from the examined tissue in response to the illuminated light radiation at a certain light detection direction, and to generate measurement data indicative thereof; at least one of said light illumination direction and detection direction is positioned at an angle of at least 20 relative to an imaginary line perpendicular to the examined tissue or form an angle of at least 20 between the light illumination direction and detection direction.
Core Innovation
The invention discloses a device for measuring biological properties of an examined tissue employing reflective measurement techniques, the device comprising at least one light source configured and operable to illuminate the examined tissue with light radiation of one or more wavelengths and a light detector located at a same side of the examined tissue configured and operable to receive light components of said one or more wavelengths reflected from the examined tissue and to generate measurement data indicative thereof. The device is configured such that at least one of the light illumination direction and detection direction is positioned at an angle relative to an imaginary line perpendicular to the examined tissue or forms an angle between the light illumination direction and detection direction, whereby proper selection of the direction and distances of the one or more light sources relative to the light detector substantially improves the magnitudes, the SNR and the AC/DC ratios of the measured optical signals. [procedural detail omitted for safety]
The background problem addressed is that conventional reflective measurement techniques suffer from low signal-to-noise ratios and low AC/DC ratios because measured signals include large DC components from light directly reflected from the organ surface and from non-perfused near-surface tissue layers. The invention solves this by arranging one or more light sources and one or more detectors in predefined orientations and distances so that most detected light components are scattered from perfused tissue layers containing blood vessels while many components reflected from non-perfused layers do not reach the detector, thereby reducing the DC component and increasing the pulsatile AC component and overall signal quality.
Claims Coverage
Two independent claims are present: an apparatus/device claim and a method claim.
Same-side reflective illumination and detection
A device comprising at least one light source configured to illuminate the examined tissue and a light detector configured to be located at a same side of the examined tissue and to receive light components reflected from the examined tissue and to generate measurement data indicative thereof.
Angled illumination or detection to favor perfused layers
At least one light source direction is positioned at an angle from the direction of light detector imaginary line perpendicular to the examined tissue or forms an angle between the light source direction and light detector direction so as to maximize the ratio between light waves reflected from blood vessels of the examined tissue and the combination of light waves reflected from other parts of the examined tissue. [procedural detail omitted for safety]
Orientation of light source away from detector
A configuration wherein the direction of the at least one light source is oriented away from the direction of the light detector.
Optimization of distance relative to angle
A position of the light source and a distance between the at least one light source and the light detector that are optimized relatively to the angle formed between the light source direction and the direction of the light detector imaginary line perpendicular to the examined tissue to collect an optimized signal from blood vessels. [procedural detail omitted for safety]
Measuring and configuring angle to maximize vessel-to-tissue ratio
A method comprising measuring the ratio between light waves reflected from blood vessels and the combination of light waves reflected from other parts of the examined tissue, configuring the angle between the at least one light source and the light detector to maximize that ratio, and then operating the device to examine the tissue, with the light source direction oriented away from the light detector and the distance optimized relative to the angle. [procedural detail omitted for safety]
The independent claims focus on a same-side reflective measurement configuration that uses angular orientation and distance optimization of light sources and detectors to maximize the proportion of light reflected from blood-containing (perfused) tissue layers versus other tissue reflections, and a method of measuring and configuring those angles/distances to maximize that ratio.
Stated Advantages
Substantially improves magnitudes of the measured optical signals.
Substantially improves signal-to-noise ratio (SNR) and AC/DC ratios of the measured signals.
Reduces baseline DC components by reducing collection of light reflected from non-perfused near-surface tissue layers and direct surface reflections.
Increases the portion of detected light scattered from perfused tissue layers containing blood vessels, thereby increasing pulsatile AC information.
Suitable for wearable and portable devices and mitigates signal distortions induced by movement of the body part/organ.
Reflective techniques offer the ability to conduct optical measurements on almost any part of the body and reduced energy consumption compared to transmissive techniques.
Experiments reported an increase in AC/DC ratio by a factor of 10 or more.
Documented Applications
Measuring heart rate.
Measuring blood flow.
Measuring arterial blood oxygen saturation (pulse oximetry).
Determining concentrations/levels of blood analytes such as glucose/sugar, cholesterol, hemoglobin, bilirubin, and fat level.
Measuring cardiac parameters including blood pressure, cardiac output, and stroke volume.
Measuring perspiration.
Use in wearable devices to be worn over body segments such as head, neck, torso, or limbs (for example, over the wrist like a watch).
Photoplethysmogram (PPG) measurements and other non-invasive blood pulse measurements.
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