Systems and methods for measuring tissue oxygenation
Inventors
Darty, Mark Anthony • YUDOVSKY, Dmitry
Assignees
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Publication Number
US-10470694-B2
Publication Date
2019-11-12
Expiration Date
Abstract
The disclosure provides methods and systems for determining tissue oxygenation. An electronic device obtains a data set including a plurality of images of a tissue of interest, each resolved at a different spectral band. Spectral analysis is performed, upon image registration, at a plurality of points in a two-dimensional area of the images of the tissue. The spectral analysis including determining approximate values of oxyhemoglobin levels and deoxyhemoglobin levels at each respective point in the plurality of points. The predetermined set of eight to twelve spectral bands includes spectral bands that provide improved methods for measuring tissue oxygenation.
Core Innovation
The invention determines tissue oxygenation by obtaining a data set that includes a plurality of images of a tissue of interest, where each image is resolved at a different spectral band. The plurality of images corresponds to a predetermined set of eight to twelve spectral bands and includes an array of pixel values. Central wavelengths and full width at half maximum constraints are defined for the spectral bands.
The method registers the plurality of images on a pixel-by-pixel basis to form a plurality of registered images of the tissue. It then performs spectral analysis at a plurality of points in a two-dimensional area of the registered images. The spectral analysis includes determining approximate values of oxyhemoglobin levels and deoxyhemoglobin levels at each respective point in the plurality of points.
In further described aspects, the spectral analysis includes correcting absorption signals for melanin contribution and correcting for loss of signal from diffuse scattering. The corrected absorption signals are then used to determine oxyhemoglobin levels and deoxyhemoglobin levels. In additional refinement, the contribution of melanin and the losses from diffuse scattering are modeled as a second order polynomial.
Claims Coverage
The document includes one independent claim that covers a processor-implemented method for determining tissue oxygenation using multiple spectral-band images, pixel-by-pixel registration, and point-wise spectral analysis to estimate oxyhemoglobin and deoxyhemoglobin. The independent claim specifies spectral-band selection constraints through central wavelengths and full width at half maximum limits.
Tissue oxygenation from pixel-registered spectral-band images
Obtaining a data set comprising a plurality of images of a tissue of interest, each resolved at a different spectral band in a predetermined set of eight to twelve spectral bands, registering the plurality of images on a pixel-by-pixel basis to form a plurality of registered images, and performing spectral analysis at a plurality of points in a two-dimensional area to determine approximate values of oxyhemoglobin levels and deoxyhemoglobin levels at each respective point.
Predetermined spectral bands with specified central wavelengths and FWHM constraints
Defining the predetermined set of eight to twelve spectral bands to include spectral bands having central wavelengths of 520±3 nm, 540±3 nm, 560±3 nm, 580±3 nm, 590±3 nm, 610±3 nm, 620±3 nm, and 660±3 nm, where the bands at 520±3 nm, 540±3 nm, 560±3 nm, 580±3 nm, 590±3 nm, 610±3 nm, and 620±3 nm have full width at half maximum of less than 15 nm, and where the band at 660±3 nm has full width at half maximum of less than 20 nm.
Optional melanin and diffuse-scattering correction before hemoglobin estimation
Correcting absorption signals for melanin contribution and for loss of signal from diffuse scattering to form a plurality of corrected absorption signals, and determining approximate oxyhemoglobin levels and deoxyhemoglobin levels at each respective point from the corrected absorption signals.
Second order polynomial modeling of melanin contribution and diffuse-scattering losses
Modeling the contribution provided by melanin and the losses provided by diffuse scattering to the plurality of tissue oxygenation measurements as a second order polynomial.
Overall, the claim coverage centers on registering multi-spectral-band tissue images pixel-by-pixel and performing point-wise spectral analysis to estimate oxyhemoglobin and deoxyhemoglobin, with spectral-band selection constrained by specified central wavelengths and full width at half maximum limits, and with optional correction/modeling for melanin contribution and diffuse-scattering signal loss.
Stated Advantages
Determines tissue oxygenation by estimating approximate oxyhemoglobin levels and deoxyhemoglobin levels at points in the tissue.
Improves oxyhemoglobin and deoxyhemoglobin estimation by correcting absorption signals for melanin contribution and loss of signal from diffuse scattering.
Provides a quantitative modeling approach for melanin contribution and diffuse-scattering losses using a second order polynomial.
Documented Applications
Not explicitly described in patent.
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