SWIP Photothermal Microscopy for Deep Tissue Vibrational Imaging
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Solution Overview
Problem
Conventional vibrational microscopy techniques face limitations in imaging depth and spatial resolution due to strong water absorption and tissue scattering, making it difficult to map chemical content in intact tissues without altering the natural microenvironment.
Innovation Solution
A short-wave infrared photothermal (SWIP) microscopy system and method using a combination of shortwave infrared excitation and probe light to generate a focused beam, which detects the SWIP signal through absorption-induced thermo-optic selective heating, allowing for millimeter-deep vibrational imaging with micron lateral resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional infrared spectroscopy-based approaches are used for vibrational microscopy, then chemical contrast from biomolecules is obtained, but imaging depth is limited to tens of micrometers due to strong water absorption
Solution Approach 1:
The patent changes the wavelength parameter of the probe light to the short-wave infrared range (1000-2500 nm), specifically targeting wavelengths where water absorption is minimized. This parameter change allows the probe light to penetrate deeper into tissue while the excitation light at different wavelengths provides the necessary chemical contrast through photothermal heating.
Solution Approach 2:
The patent introduces a photothermal intermediary mechanism where excitation light is absorbed by biomolecules to generate localized heat, which then modulates the refractive index of the surrounding medium. This thermal intermediary allows indirect detection of chemical composition at depths where direct infrared absorption would be blocked by water.
2Length of stationary object
If spontaneous or coherent Raman microscopy with visible or near-infrared excitation is used, then imaging depth reaches around 100 μm, but spatial resolution is limited due to large tissue scattering
Solution Approach 1:
The patent employs periodic pulsed excitation light to generate photothermal effects, creating time-resolved thermal lensing that enhances spatial resolution. The periodic heating and cooling cycles allow temporal gating of the signal, separating the photothermal response from scattered background light and improving effective spatial resolution despite tissue scattering.
3Length of stationary object
If spatially offset Raman spectroscopy or spontaneous Raman tomography is used to acquire signals beyond millimeter-deep in tissue, then imaging depth is improved, but spatial resolution degrades to millimeter-level
Solution Approach 1:
The patent adds the temporal dimension to the detection process by measuring the time-dependent photothermal response. The thermal lens formed by photothermal heating has a characteristic decay time that provides temporal discrimination, allowing subcellular spatial resolution to be achieved even at millimeter imaging depths by analyzing the time-resolved thermal response rather than relying solely on spatial filtering.
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
SWIP achieves subcellular-resolution and millimeter-level penetration in highly scattering mediums, enabling imaging of single 1-μm polystyrene beads and intracellular lipids in intact tumor spheroids and thick tissues, with improved sensitivity and spatial resolution compared to existing methods.
Implementation Method 1
obtain a SWIP signal generated by absorption-induced thermo-optic selective heating of the sample
Implementation Method 2
absorption-induced thermo-optic selective heating
Implementation Method 3
An objective receives the combined beam and focuses the combined beam to generate a focused combined beam
Implementation Method 4
An objective receives the combined beam and focuses the combined beam
Implementation Method 5
A condenser for collects the SWIP signal through an aperture in the condenser
Implementation Method 6
A detection element for detects the SWIP signal from the condenser
Data Source
AI summary
A short-wave infrared photothermal (SWIP) microscopy system and method for vibrational imaging of a sample generates shortwave infrared excitation light probe light. The excitation light and the probe light are combined to generate a combined beam, which is focused to generate a focused combined beam, which is directed onto the sample to obtain a SWIP signal generated by absorption-induced thermo-optic selective heating of the sample. The SWIP signal is collected through an aperture in a condenser and detected.