Optical Coherence Elastography for Ocular Tissue Stiffness
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Solution Overview
Problem
Current methods for assessing the mechanical properties of ocular tissues, such as the cornea and crystalline lens, are limited by low spatial resolution and inability to differentiate tissue stiffness influenced by intraocular pressure, making it challenging to diagnose and monitor degenerative diseases like keratoconus and presbyopia effectively.
Innovation Solution
Optical coherence elastography (OCE) uses high-resolution optical coherence tomography to measure tissue displacement induced by external forces, providing superior spatial imaging and faster acquisition speeds to quantify biomechanical properties non-invasively, distinguishing between corneal stiffness due to disease or UV-induced collagen cross-linking and intraocular pressure effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasound elastography is used to measure tissue mechanical properties, then measurement capability is provided, but spatial resolution is low
Solution Approach 1:
The patent replaces ultrasound-based mechanical elastography with an optical measurement system (OCT-based optical coherence elastography). This substitution transitions from acoustic wave-based mechanical probing to optical interferometry-based displacement measurement, thereby achieving high spatial resolution comparable to OCT imaging while maintaining elastography functionality.
2Measurement precision
If conventional elastography is used to assess tissue stiffness, then overall stiffness measurement is achieved, but inability to differentiate stiffness influenced by intraocular pressure exists
Solution Approach 1:
The patent segments the elastography measurement into multiple independent components: (1) OCT-based displacement field measurement, (2) acoustic radiation force application, and (3) intraocular pressure measurement. This segmentation allows each parameter to be measured and analyzed separately, enabling differentiation between stiffness changes due to disease, treatment, or IOP variations.
Solution Approach 2:
The system incorporates feedback by measuring intraocular pressure concurrently with tissue displacement and using this information to compensate for IOP-related artifacts in the stiffness calculation. The measured IOP values are fed back into the elastography analysis to distinguish true tissue stiffness changes from pressure-induced artifacts.
3Manufacturing precision
If high-resolution optical coherence tomography is used for imaging, then spatial resolution is improved, but acquisition speed may be reduced
Solution Approach 1:
The patent employs periodic action by using a swept-source laser that rapidly tunes through a wavelength range in a periodic manner. This allows the OCT system to acquire depth information at high speeds by continuously sweeping the laser wavelength, thereby maintaining high acquisition rates despite the complexity of high-resolution imaging.
Solution Approach 2:
The system maintains continuous useful action by performing rapid sequential A-scan acquisitions across the tissue region of interest. The swept-source OCT continuously sweeps through wavelengths and acquires interference signals without interruption, enabling real-time elastography measurement while preserving high spatial resolution through dense sampling.
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
OCE enables precise, non-invasive assessment of tissue stiffness with high sensitivity and resolution, allowing for early detection of ocular diseases and effective monitoring of treatments like UV-induced collagen cross-linking, while minimizing ultrasound damage and optimizing refractive surgeries.
Implementation Method 1
Optical coherence elastography (OCE) uses high-resolution optical coherence tomography to measure tissue displacement induced by external forces
Implementation Method 2
measure tissue displacement induced by external forces
Data Source
AI summary
An excitation force (internal or external) and phase-sensitive optical coherence elastography (OCE) system, used in conjunction with a data analyzing algorithm, is capable of measuring and quantifying biomechanical parameters of tissues in situ and in vivo. The method was approbated and demonstrated on an example of the system that combines a pulsed ultrasound system capable of producing an acoustic radiation force on the crystalline lens surface and a phase-sensitive optical coherence tomography (OCT) system for measuring the lens displacement caused by the acoustic radiation force. The method allows noninvasive and nondestructive quantification of tissue mechanical properties. The noninvasive measurement method also utilizes phase-stabilized swept source optical coherence elastography (PhS-SSOCE) to distinguish between tissue stiffness, such as that attributable to disease, and effects on measured stiffness that result from external factors, such as pressure applied to the tissue. Preferably, the method is used to detect tissue stiffness and to evaluate the presence of its stiffness even if it is affected by other factors such as intraocular pressure (TOP) in the case of cornea, sclera, or the lens. This noninvasive method can evaluate the biomechanical properties of the tissues in vivo for detecting the onset and progression of degenerative or other diseases (such as keratoconus).