Method and device for correcting optical signals
Inventors
Kintz, Gregory J. • McMillan, William • Wisniewski, Natalie
Assignees
Publication Number
US-10045722-B2
Publication Date
2018-08-14
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
An optical device and method for monitoring an implant embedded in tissue transmit excitation light within an excitation wavelength range to the implant and measure emitted light within an emission wavelength range, including an analyte-dependent optical signal, and calculate at least one corrected signal value in dependence upon measured signals. The device has an arrangement of light sources, filters and detectors to transmit excitation light and to measure emitted light, and the light sources, filters and detectors may also be used to monitor autofluorescence in the tissue to correct autofluorescence background.
The invention provides transmitting first excitation light within the excitation wavelength range to the implant and measuring a first optical signal emitted from the tissue within the emission wavelength range, 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, and calculating at least one corrected signal value in dependence upon the measured signals to correct the analyte-dependent optical signal for diffuse reflectance, scattering, autofluorescence, and/or background light.
The background problem being solved is that implanted sensors are often difficult to read or to monitor optically because of low levels of fluorescence in the presence of high scatter due to dynamic changes in skin conditions such as blood level and hydration, and that there is a need for a small, compact device that can accurately and consistently monitor an implanted sensor and provide signals to an analyzer without substantially restricting movements and activities of a patient.
Claims Coverage
The claims include four independent claims. The main inventive features extracted from the independent claims are presented below (eight inventive features in total).
Sensor patch with central first and second light sources
A sensor patch including a case with a first light source disposed within the case and located within a center portion pre-configured to generate a first optical signal within an excitation wavelength range to illuminate an implant containing a luminescent dye, and a second light source disposed within the case and located within the center portion pre-configured to generate a second optical signal within the emission wavelength range to illuminate the tissue.
Ring-configured detectors receiving implant and tissue emission signals
A plurality of detectors disposed within the case in a ring configuration around the central portion, a first detector from the plurality of detectors configured to receive a third optical signal emitted from the implant within the emission wavelength range in response to the implant being illuminated with the first optical signal and to receive a fourth optical signal in response to the tissue being illuminated by the second optical signal within the emission wavelength range.
Plurality of light sources and detectors in outer ring and central portion
A case with a plurality of light sources and detectors disposed within the case, each detector disposed adjacent to a light source in a ring configuration in an outer ring portion of the case, and a first light source disposed within a first portion of the case pre-configured to generate a first optical signal within a first excitation wavelength range to illuminate an implant that emits an analyte-dependent optical signal within a first emission wavelength range.
Mutually exclusive portions defining laterally spaced light paths
A second light source pre-configured to generate a third optical signal to illuminate the implant with a second excitation wavelength range and a second detector disposed within a second portion of the case configured to receive a fourth optical signal within a second emission wavelength range, the first portion and the second portion mutually exclusive such that the first optical signal and the second optical signal define light paths that are spaced laterally apart.
Detectors adjacent to light sources in outer ring with central excitation
A sensor patch with a plurality of detectors disposed adjacent to light sources in a ring configuration in an outer ring portion of the case, a first light source configured to generate a first optical signal within an excitation wavelength range to illuminate an implant and a second light source configured to generate a second optical signal within the emission wavelength range to illuminate the tissue, with a first detector configured to receive both implant-emitted and tissue-emitted optical signals within the emission wavelength range.
Laterally spaced second light path that avoids implant contribution
A third light source and a second detector disposed in a second portion mutually exclusive from the first portion such that the third optical signal and the sixth optical signal travel a second light path that is spaced laterally from the implant when the first light source illuminates the implant so that the second light path does not include a significant contribution from the implant.
Central first light source with plurality of ring detectors and analyte-independent reporter handling
A case with a first light source disposed within a center portion pre-configured to generate a first optical signal within a first excitation wavelength range to illuminate an implant configured to emit an analyte-dependent optical signal within a first emission wavelength range and an analyte-independent optical signal within a second emission wavelength range, and a plurality of detectors disposed within the case in a ring configuration around the central portion.
Separate detector and light source pair for analyte-independent signal with lateral spacing
A second light source pre-configured to generate a third optical signal to illuminate the implant with the second excitation wavelength range and a second detector disposed within a second portion of the case configured to receive a fourth optical signal emitted from the implant within the second emission wavelength range, the second portion being mutually exclusive such that the first optical signal and the second optical signal define light paths that are spaced laterally apart.
The independent claims collectively cover a sensor patch device architecture with centered excitation light sources, ring-configured detectors (including outer-ring detectors), combinations of light-source/detector pairings that define light paths to specific tissue depths, and arrangements that provide laterally spaced light paths to measure implant-emitted signals and tissue reference signals for correction of analyte-dependent optical signals.
Stated Advantages
Correcting the analyte-dependent signal by one or more reference signals enables accurate and/or consistent glucose values to be determined from measurements of light emitted from an implant located relatively deep in the tissue, such as in the subcutaneous region.
Measurements of the reference optical signals used for correction factors are taken in the same region of tissue in which the implant is embedded in a few seconds or less, so that dynamic skin or tissue properties are substantially the same for the correction signals as they are for the primary analyte-dependent signal at the time of measurement.
Documented Applications
Monitoring an implant embedded in the tissue of a mammalian body to detect an analyte-dependent optical signal, where the analyte may comprise glucose, lactate, or oxygen.
Continuous and/or automatic monitoring of analyte levels (for example glucose) to provide a warning to the patient when the level of the analyte is at or near a threshold level such as current or impending hyperglycemia or hypoglycemia.
Use in device 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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