Common-Path Interferometer for Catheter OCT Stability

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Solution Overview

Problem

Conventional fiber optic OCT systems face issues with path length, dispersion, and polarization mismatches when the catheter is bent or twisted, leading to image drift, signal loss, and reduced resolution.

Innovation Solution

A common-path interferometer design where the reference and sample arms traverse the same path within the probe, minimizing path length mismatches and maintaining dispersion and polarization balance, using a narrowband light source and optical elements like refractive index interfaces and circulators to ensure balanced signal propagation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the catheter is bent or twisted to access internal organs, then adaptability is improved, but path length mismatch and dispersion mismatch increase leading to image drift and resolution loss

Engineering Contradiction:

Improvecatheter flexibilityVSAvoidimage resolution

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent merges the reference arm and sample arm into a common optical path by placing both arms within the same catheter body. The reference mirror and sample interface are positioned such that both optical paths traverse the same fiber optic elements, eliminating path length and dispersion mismatches that occur when the catheter is bent or twisted.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent segments the optical paths within the catheter by using separate fiber optic elements for the reference arm and sample arm, but routes them through the same physical space and environmental conditions, allowing independent optimization of each arm while maintaining environmental symmetry.

Inventive Principle:

Principle #1Segmentation

2Device complexity

If conventional separate path interferometers are used, then device complexity is reduced, but path length stability deteriorates when the catheter moves

Engineering Contradiction:

Improveinterferometer structureVSAvoidpath length stability

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The patent combines both optical arms within the same catheter structure, sharing common environmental conditions and physical constraints. This merging ensures that when the catheter moves or deforms, both arms experience identical changes, maintaining path length stability without requiring complex external stabilization mechanisms.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If time domain OCT scanning is used to achieve high resolution, then measurement precision is improved, but imaging speed decreases due to rapid scanning requirements

Engineering Contradiction:

Improveaxial resolutionVSAvoidimaging speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces the mechanical scanning system of time domain OCT with a frequency domain approach using spectral interferometry. By detecting the spectral interference pattern and applying Fourier transformation, the system achieves high axial resolution without requiring rapid mechanical scanning of the reference arm, thereby significantly improving imaging speed.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This design stabilizes the image, maintains high resolution, and increases imaging speed by eliminating the need for rapid scanning, reducing motion artifacts and enhancing usability in clinical settings.

Implementation Method 1

Interference fringes may be detected when the sample arm path length matches the reference arm path length to within the coherence length of the light

Methodology Applied

Scientific EffectInterference: Interference

Implementation Method 2

Fourier transformation of such spectral interference pattern can result in an axial reflectivity profile

Methodology Applied

Scientific EffectFourier transformation:

Data Source

PatentUS7995210B2Devices and arrangements for performing coherence range imaging using a common path interferometer

Publication Date: 2011.08.09 THE GENERAL HOSPITAL CORP

AI summary

Devices, arrangements and apparatus adapted to propagate at least one electro-magnetic radiation are provided. In particular, a probe housing, a sample arm section and a reference arm section can be included. For example, the sample arm section can be at least partially situated within the probe housing, and configured to propagate a first portion of the electro-magnetic radiation that is intended to be forwarded to a sample. The reference arm section can be at least partially situated within the probe housing, and configured to propagate a second portion of the electro-magnetic radiation that is intended to be forwarded to a reference. In addition or as an alternative, an interferometer may be situated within the probe housing. The first and second portions may travel along substantially the same paths, and the electro-magnetic radiation can be generated by a narrowband light source that has a tunable center wavelength. Further, the first and second portions may be at least partially transmitted via at least one optical fiber. A splitting arrangement may be provided which splits the electro-magnetic radiation into the first and second portions, and positioned closer to the sample than to the source of the electro-magnetic radiation, and the first and second portions may be adapted to propagate in different directions. An apparatus may be provided that is configured to control an optical path length of the second portion.