Apparatus and methods for detecting optical signals from implanted sensors
Inventors
Kintz, Gregory J. • McMillan, William A. • Wisniewski, Natalie A.
Assignees
Publication Number
US-10219729-B2
Publication Date
2019-03-05
Expiration Date
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Abstract
Some embodiments described herein relate to an apparatus including a light source configured to transmit an excitation optical signal to an implanted sensor and a detector configured to detect an analyte-dependent optical signal emitted from an implanted sensor. The apparatus can include a lens configured to focus at least a portion of the analyte-dependent optical signal onto the detector.
Core Innovation
Some embodiments relate to an apparatus including a light source configured to transmit an excitation optical signal to an implanted sensor and a detector configured to detect an analyte-dependent optical signal emitted from an implanted sensor, and can include a lens configured to focus at least a portion of the analyte-dependent optical signal onto the detector. Devices and apparatus described herein are suitable for providing accurate and consistent measurement of an analyte by monitoring an implantable sensor in low-signal, high-scattering environments. The optical detection device can be operable to illuminate the implant with light whose wavelength content falls within an absorption band and/or collect light whose wavelength content is in an emission band.
The patent describes problems with conventional monitoring including inconvenience of periodic blood testing and challenges of implanted sensors that use RF communications which may increase bulk and require batteries. The patent further identifies difficulty in optically reading fluorescent implanted sensors because of low levels of fluorescence in the presence of high scatter due to dynamic changes in skin conditions and because existing optical filter technology and standard fluorescence methods can result in low signal-to-background and signal-to-noise ratios. The skin is described as highly scattering where scattering and absorption by tissue components can dominate optical propagation and reduce detectable fluorescence.
To address these problems, embodiments disclose optical system elements arranged to restrict off-axis light and wavelength content reaching detectors, including arrays of lenses aligned with arrays of apertures, light control film layers, filters, and light-blocking elements disposed to inhibit photons having angles of incidence greater than predetermined angles. Embodiments also describe arrangements wherein excitation light is transmitted through a first surface area of skin and detected light is collected through a second surface area of skin that is larger (e.g., at least four times) to improve detection, and configurations such as a patch with a central via for excitation and surrounding detectors to increase collection area. The patent further describes monolithically formed lens arrays, use of dichroic or dielectric filters, and options for wearable, continuous monitoring devices that can be configured as patch readers, hand-held readers, bench-top instruments, imaging systems, or smartphone attachments.
Claims Coverage
Overview: Three independent claims were identified, each reciting an apparatus or system combining excitation and detection optics with specific spatial, angular, and lens-array arrangements to improve detection of analyte-dependent optical signals from an implanted sensor.
Detection surface area at least four times excitation surface area
a planar base; a light source coupled to the planar base and configured to transmit an excitation optical signal through a first surface area of skin to an implanted sensor; one or more detectors coupled to the planar base and configured to detect an analyte-dependent optical signal emitted from the implanted sensor through a second surface area of skin in response to the implanted sensor being illuminated by the excitation optical signal, the second surface area of the skin being at least four times the first surface area of the skin
Array of lenses with non-coaxial parallel lens axes
a first lens from an array of lenses, the first lens configured to focus at least a portion of the analyte-dependent optical signal onto at least one of the one or more detectors, the first lens defining a first lens axis; and a second lens from the array of lenses, the second lens configured to focus at least a portion of the analyte-dependent optical signal onto at least one of the one or more detectors, the second lens defining a second lens axis substantially parallel to and non-coaxial with the first lens axis
Detector spacing at least twice the implant depth
a light source configured to transmit an excitation optical signal to a sensor implanted at a depth of at least 1 mm under a surface of a skin; a detector configured to detect an analyte-dependent optical signal emitted from the sensor in response to the sensor being illuminated by the excitation optical signal, at least a portion of the detector spaced at least 2 mm from the light source such that at least the portion of the detector is spaced apart from the light source at least twice the depth of the sensor; a monolithically formed array of lenses disposed between the cover and the detector, a lens from the monolithically formed array of lenses configured to focus a portion of the analyte-dependent optical signal onto the detector
Base defining an opening with excitation through opening
a light source configured to transmit an excitation optical signal to an implanted sensor; a base defining an opening, the light source configured to transmit the excitation optical signal to the implanted sensor through the opening; one or more detectors coupled to the base and configured to detect an analyte-dependent optical signal emitted from the implanted sensor in response to the implanted sensor being illuminated by the excitation optical signal
The independent claims focus on (1) arranging excitation and detection areas such that the detected surface area is at least four times the excitation area, (2) using lens arrays with lenses having parallel but non-coaxial axes to focus analyte-dependent optical signals onto detectors, (3) specific detector spacing relative to implant depth and monolithically formed lens arrays, and (4) a base with an opening for excitation transmission—each combined to restrict off-axis and unwanted light and improve detection of implanted sensor emissions.
Stated Advantages
Provide accurate and consistent measurement of an analyte by monitoring an implantable sensor in low-signal, high-scattering environments.
Enable continuous and/or automatic monitoring and can be worn by a user substantially continuously without substantially restricting movements or activities.
Provide a warning to the person when the level of the analyte is at or near a threshold level (e.g., to warn of hyperglycemia or hypoglycemia).
Improve detection of implant signals by using a relatively large ratio of detector surface area to excitation surface area (e.g., at least 4:1).
Improve detection accuracy by capturing a larger portion of an emitted signal in high-scattering environments.
Minimize photons from the light source reaching the detectors and prevent scattered excitation light from blinding the detector via filters, aperture arrays, light control films, and light-blocking elements.
Documented Applications
Monitoring analyte levels (for example glucose, lactate, oxygen) in tissue using an implanted fluorescent sensor.
Continuous glucose monitoring for persons with diabetes, including providing warnings of current or impending hyperglycemia or hypoglycemia.
Wearable reader implementations such as a patch configured to be placed on the skin, including wireless skin patch readers and hand-held readers.
Bench-top instruments, imaging systems, smartphone attachments and applications, or other configurations that utilize the disclosed optics and algorithms.
Monitoring an implant embedded in tissue of a mammalian body (e.g., subcutaneous implants).
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