Method and device for correcting optical signals
Inventors
Kintz, Gregory J. • McMillan, William • Wisniewski, Natalie
Assignees
Publication Number
US-12059254-B2
Publication Date
2024-08-13
Expiration Date
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Abstract
An optical device is used to monitor an implant embedded in the tissue of a mammal (e.g., under the skin). The implant receives excitation light from the optical device and emits light that is detected by the optical device, including an analyte-dependent optical signal. Scatter and absorption properties of tissue change over time due to changes in hydration, blood perfusion and oxygenation. The optical device has an arrangement of light sources, filters and detectors to transmit excitation light within excitation wavelength ranges and to measure emitted light within detection wavelengths. Changes in scattering and absorption of light in the tissue, such as diffuse reflectance, are monitored. The light sources, filters and detectors may also be used to monitor autofluorescence in the tissue to correct autofluorescence background.
Core Innovation
A method and optical detection device for correcting at least one analyte-dependent optical signal emitted from an implant embedded in tissue of a mammalian body is provided. The implant is capable of emitting, in response to excitation light within an excitation wavelength range, the analyte-dependent optical signal within an emission wavelength range. The method comprises transmitting first excitation light within the excitation wavelength range through the tissue to the implant and measuring a first optical signal emitted from the tissue, within the emission wavelength range, in response to the first excitation light; transmitting second excitation light within the emission wavelength range into the tissue and measuring a second optical signal emitted from the tissue, within the emission wavelength range, in response to the second excitation light; and calculating at least one corrected signal value in dependence upon the measured signals.
An optical detection device is described that comprises a first light source arranged to transmit first excitation light in the excitation wavelength range through the tissue to the implant, a second light source arranged to transmit second excitation light within the excitation or emission wavelength range into the tissue, and at least one detector arranged to measure, in response to the first and second excitation light, respective optical signals emitted from the tissue within selected wavelength ranges. Embodiments include use of analyte-independent or stable reference reporter signals, measurements for diffuse reflectance, autofluorescence, and exciter power normalization, and positioning of source/detector pairs such that certain light paths are laterally spaced from the implant to avoid significant contribution from implant reporters. At least one corrected signal value is calculated from combinations of the measured optical signals to determine analyte concentration using look-up tables or calibration curves.
Claims Coverage
The patent discloses two independent claim sets; the following summarizes two main inventive features derived from those independent claims.
Device with dual excitation and correction processing
A device comprising a housing, a first light source configured to emit a first optical signal with a predefined excitation wavelength to illuminate an implanted sensor that emits an analyte-dependent optical signal with a predefined emission wavelength (different from the excitation), a second light source configured to emit a second optical signal with the predefined emission wavelength into tissue, and at least one detector configured to (1) receive the analyte-dependent optical signal and backscatter from the second optical signal and (2) receive an analyte-independent signal emitted by the implanted sensor in response to the first optical signal; and a processor configured to receive data representative of the analyte-dependent, backscatter, and analyte-independent signals, calculate a correction factor using at least one of the backscatter or analyte-independent data, and calculate a quantity or concentration of analyte by applying the correction factor to the analyte-dependent data.
Device with separate excitation wavelengths and spatially offset reference detection
A device comprising a housing, a first light source emitting a first excitation to elicit an analyte-dependent emission, a second light source emitting a second excitation to elicit an analyte-independent emission with distinct predefined wavelengths, a third light source spaced apart such that when the first and second light sources illuminate the implant the third source produces a fourth optical signal associated with tissue (e.g., autofluorescence or backscatter) that is detectable without significant contribution from the implant, at least one detector configured to receive the analyte-dependent, analyte-independent, and the fourth optical signals, and a processor configured to calculate a correction factor based on at least one of the analyte-independent or the fourth optical signal and to calculate analyte quantity or concentration by applying the correction factor to the analyte-dependent signal.
The independent claims cover optical detection devices that combine multiple light sources (separate excitation and emission-wavelength illumination), detectors that capture analyte-dependent emissions plus tissue backscatter/autofluorescence and analyte-independent reference signals, and processors that compute correction factors from those measured signals to determine analyte quantity or concentration.
Stated Advantages
Corrects primary analyte-dependent optical signals for diffuse reflectance and/or autofluorescence using reference optical signals.
Enables accurate and/or consistent analyte (e.g., glucose) values from measurements of light emitted from an implant located relatively deep in tissue by applying correction factors.
Permits reference optical signals used for correction to be taken in the same region of tissue and within a few seconds so that dynamic skin or tissue properties are substantially the same for correction and primary measurements.
Provides means to correct for modulation of light emitted from tissue in addition to correction for excitation light and background or ambient light.
Documented Applications
Monitoring an implant embedded in tissue to determine analyte levels such as glucose, lactate, or oxygen.
Continuous and/or automatic monitoring of analyte levels to provide a warning to the patient when the analyte level is at or near a threshold (e.g., warning of current or impending hyperglycemia or hypoglycemia).
Use in small, compact devices that monitor an implanted sensor and provide signals to an analyzer without substantially restricting patient movements and activities.
Configurations including cabled or wireless hand-held readers, wireless skin patch readers, bench-top instruments, imaging systems, handheld devices (e.g., cell phones or mobile communication devices), smartphone attachments and applications.
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