Depth Scanning Oxygen Sensor with Optical Phosphorescence
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Solution Overview
Problem
Current medical devices lack the capability to reliably and accurately measure tissue oxygen levels at multiple locations along a linear path within tissue depth without mechanical motion, sustaining tissue pressures, and providing prolonged and precise monitoring of oxygen distribution, which is crucial for effective disease diagnosis and treatment planning.
Innovation Solution
A tissue oxygen sensor with a rugged design that uses optical phosphorescence sensing, incorporating an oxygen-sensitive dye in a polymer matrix within a glass capillary coated on a stainless steel needle, allowing for continuous monitoring and depth-resolved pO2 measurement without mechanical translation, featuring a separate optical fiber for excitation and emission, and a console unit for digital signal processing and motorized scanning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If polarographic oxygen electrodes are used to directly measure tissue oxygen, then measurement precision is improved, but the device consumes oxygen during operation which reduces reliability for prolonged monitoring
Solution Approach 1:
The patent replaces the electrochemical polarographic electrode system with an optical phosphorescence sensing system. The optical fiber delivers excitation light to the phosphorescent dye, and the emitted phosphorescence is detected optically, eliminating the need for electrochemical reactions that consume oxygen. This substitution enables prolonged monitoring without oxygen consumption while maintaining measurement precision.
Solution Approach 2:
The patent introduces a phosphorescent dye as an intermediary substance that mediates between the optical excitation and oxygen detection. The dye absorbs excitation light and emits phosphorescence whose lifetime is modulated by oxygen concentration, allowing indirect but non-consuming measurement of tissue oxygen levels.
2Measurement precision
If a needle is re-inserted into tissue to repeat oxygen measurements at multiple locations, then measurement precision at each point is improved, but tissue damage occurs which alters oxygen levels and reduces reliability
Solution Approach 1:
The patent segments the sensing capability along the length of a single needle by incorporating a longitudinal array of phosphorescent dyes at different positions. The optical fiber can be translated along the needle to excite and detect phosphorescence from dyes at various depths, enabling multiple measurement points without re-insertion and thereby avoiding additional tissue damage.
Solution Approach 2:
The patent introduces dynamic translation of the optical fiber along the stationary needle to access different sensing zones. This dynamic positioning allows the system to measure oxygen at multiple locations along the needle length without moving the needle itself, eliminating the need for repeated tissue punctures.
3Reliability
If optical fiber is used for phosphorescence sensing, then reliability for prolonged monitoring is improved, but mechanical stability deteriorates under tissue pressures
Solution Approach 1:
The patent protects the optical fiber by embedding it within a flexible glass capillary tube. This thin-walled protective shell shields the fragile fiber from mechanical damage while allowing flexibility and biocompatibility, enabling the device to withstand tissue pressures during prolonged implantation.
Solution Approach 2:
The patent creates a composite structure combining the optical fiber, glass capillary protection, and phosphorescent dye layer. This multi-material composite provides both the optical functionality and the mechanical robustness needed to survive insertion and prolonged operation in tissue environments.
4Measurement precision
If multiple dyes are used to resolve depth distribution of oxygen, then measurement precision for spatial distribution is improved, but device complexity increases
Solution Approach 1:
The patent adds the spatial dimension along the needle length to the sensing capability by positioning phosphorescent dyes at different longitudinal locations. This transforms the sensing from a single-point measurement to a distributed spatial measurement, enabling depth-resolved oxygen mapping without requiring complex multi-dimensional sensor arrays.
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
Enables direct, prolonged, and spatially resolved measurement of tissue oxygen levels, minimizing tissue damage, providing precise diagnostic information for various medical conditions, including wound healing and cancer diagnosis, with improved mechanical stability and sensitivity.
Implementation Method 1
Optical phosphorescence sensing has emerged as an alternative oxygen sensing technology to polarographic electrodes. Phosphorescence emission of many types of dyes is effectively quenched by oxygen. The rate of phosphorescence quenching is linearly dependent on oxygen concentration
Implementation Method 2
The photophysics of the oxygen quenching process can be described as follows. A dye molecule is excited by absorbing a photon which leads to a change in the electron state of the dye from a ground state to a higher energy singlet state. The higher energy state can switch from the singlet state into a triplet state, a process known as intersystem crossing. The triplet state eventually relaxes back to ground state by emitting a phosphorescence photon. In the presence of oxygen, energy transfer to oxygen through collisions competes with phosphorescence emission.
Data Source
AI summary
An oxygen scanning device includes a console unit. The console unit includes a light source emitting excitation radiation and a detector configured to receive and detect phosphorescence radiation. The device includes a needle sensor operably, optically coupled to the console unit by an optical fiber movably received within a transparent tube housing the optical fiber, the transparent tube being coated by an oxygen-sensitive dye material on an outer side thereof. The optical fiber is terminated by a 45 degree reflecting surface at a distal end thereof wherein excitation radiation is directed to the oxygen sensitive dye material and phosphorescence radiation from the oxygen sensitive material is returned from the oxygen sensitive material to the detector.