Methods For Implementing Standardised Time Domain Diffuse Optical Spectroscopy In Wearables/Portables
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Solution Overview
Problem
Current wearable biophotonic devices face challenges with inaccurate and unreliable optical property measurements due to motion artifacts, skin pigmentation, and scattering variability, which are exacerbated by the use of continuous wave (CW) technology, while time domain (TD) methods offer more accurate measurements but are complex and impractical for wearables due to low photon count rates and slow data acquisition.
Innovation Solution
A portable/wearable device implementing standardised time domain diffuse optical spectroscopy with a pulsed or modulated light source, high photon count rate photodetection system, and a processing circuit to measure time of flight (ToF) distributions, using tissue mimicking phantoms for calibration and compensation, enabling accurate extraction of optical properties and biomarkers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If continuous wave (CW) diffuse optical spectroscopy is used in wearable devices, then instrumentation simplicity and cost are improved, but measurement accuracy and reliability deteriorate due to motion artifacts and skin pigmentation effects
Solution Approach 1:
The patent transitions from continuous wave (CW) measurements to time domain (TD) measurements, fundamentally changing the measurement parameter from intensity to temporal profile. This allows separation of absorption and scattering coefficients by analyzing the shape and timing of light pulses, thereby improving measurement accuracy while maintaining wearable device simplicity
Solution Approach 2:
The patent implements preliminary calibration using tissue-mimicking phantoms with known optical properties before actual measurements. This calibration process compensates for device-specific variations and enables accurate extraction of optical properties from the measured temporal profiles, addressing the accuracy issues of CW measurements
2Measurement precision
If time domain (TD) diffuse optical spectroscopy is implemented in wearable devices, then measurement accuracy is improved, but device complexity and impracticality increase due to low photon count rates and slow data acquisition
Solution Approach 1:
The patent uses tissue-mimicking phantoms as simplified copies of biological tissue with known optical properties. These phantoms serve as calibration standards that replicate the optical characteristics of real tissue without the complexity of in vivo measurements, enabling accurate calibration and validation of the TD measurement system
Solution Approach 2:
The patent employs periodic pulsed light illumination rather than continuous illumination. By using repeated light pulses and analyzing the temporal response, the system achieves high photon count rates and fast data acquisition, overcoming the limitations of traditional TD methods while maintaining measurement accuracy
3Measurement precision
If conventional TD measurement methods are used, then optical property separation is achieved, but photon count rates remain low and data acquisition is slow
Solution Approach 1:
The patent uses periodic pulsed light illumination to enable high photon count rates. By repeatedly pulsing the light source and using fast photodetectors to capture the temporal response, the system achieves both accurate optical property separation and rapid data acquisition, overcoming the inherent slowness of conventional TD methods
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device provides robust and accurate measurements of physiological parameters by compensating for motion artifacts, skin pigmentation, and scattering effects, achieving high photon count rates without pile-up, and integrating CW and TD measurement modes for enhanced accuracy and reliability.
Implementation Method 1
When light in the NIR spectral window interacts with tissue, it undergoes scattering and absorption dependent on the presence and concentration of certain tissue constituents
Implementation Method 2
When light in the NIR spectral window interacts with tissue, it undergoes scattering and absorption dependent on the presence and concentration of certain tissue constituents
Implementation Method 3
The processing circuit is configured to measure or generate a time of flight distribution of photons detected in response to the light beam being directed towards the target region
Implementation Method 4
measuring a time of flight distribution for photons detected in response to a pulsed or modulated beam of light being directed towards a target region of the body; extracting one or more optical properties of the target region from the measured time of flight distribution
Data Source
AI summary
Disclosed is a wearable device configured to perform standardised time domain diffuse optical spectroscopy, comprising an illumination system with a light source configured to illuminate a target region of the body, a photodetection system configured to detect scattered light exiting the target region and provide a measurement signal, and a processing circuit for time of flight (ToF) data acquisition. At least a portion of the beam is coupled to the photodetection system via a first reference optical path comprising a tissue mimicking phantom with one or more known optical properties to provide a first reference signal. The processing circuit measures a ToF distribution for photons detected from the target region and determines one or more optical properties of the target region from measured ToF distribution; measures a ToF distribution for photons detected from the phantom and determines one or more calibration factors for use in determining the one or more optical properties of the target region; and determines one or more optical biomarker values based, at least in part, on the one or more optical properties of the target region.