Photoacoustic Remote Sensing for Non-Contact Microscopy
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Solution Overview
Problem
Current photoacoustic imaging systems require physical contact or ultrasound coupling media, which is impractical for clinical applications like wound healing and endoscopic procedures, and lack non-contact in vivo microscopy with optical resolution and practical signal-to-noise ratio.
Innovation Solution
The photoacoustic remote sensing (PARS) system uses co-focused excitation and interrogation beams to detect pressure-induced refractive-index modulation subsurface, eliminating the need for contact or coupling media and achieving optical-resolution imaging without interferometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional photoacoustic imaging systems use piezoelectric transducers with ultrasound coupling media, then ultrasound detection sensitivity is improved, but ease of operation deteriorates due to requirement of physical contact and coupling media
Solution Approach 1:
The patent replaces the mechanical piezoelectric transducer system with an optical detection system. Specifically, it uses a laser beam to probe the photoacoustic waves and detect refractive index changes caused by pressure variations in the tissue, eliminating the need for mechanical contact and ultrasound coupling media while maintaining detection capability
Solution Approach 2:
The patent introduces light (laser beam) as an intermediary to detect photoacoustic waves. Instead of directly measuring mechanical pressure with transducers, the system uses light refractive index changes as a mediator to indirectly detect the photoacoustic signals, enabling non-contact measurement
2Ease of operation
If optical interferometric methods are used to detect photoacoustic signals non-contact, then ease of operation is improved, but measurement precision deteriorates due to sensitivity to unwanted vibrations and complex amplitude reflectivity modulations
Solution Approach 1:
Instead of detecting surface oscillations as done in traditional interferometric methods, the patent inverts the approach by detecting the photoacoustic waves themselves through refractive index changes in the subsurface tissue. This is achieved by probing with a laser beam at a specific depth and measuring phase or intensity changes caused by pressure-induced refractive index variations, rather than measuring surface motion
Solution Approach 2:
The patent extracts only the relevant photoacoustic signal information by using short-coherence-length light to probe at a specific depth, isolating the signal from the excitation region. This extracts the useful photoacoustic information while rejecting unwanted vibrations and background noise that affect surface-based interferometric methods
3Manufacturing precision
If OR-PAM is used to achieve micron-scale resolution, then manufacturing precision is improved, but depth penetration deteriorates due to fundamental limitations of light transport
Solution Approach 1:
The patent segments the imaging process into distinct excitation and detection regions. The excitation laser creates photoacoustic signals at a specific depth, while the detection laser probes a separate region. This segmentation allows independent optimization of excitation depth and detection resolution, enabling both deep penetration and micron-scale resolution
Solution Approach 2:
The patent transitions from direct optical imaging to a hybrid photoacoustic-optical approach. By converting optical energy to acoustic waves (photoacoustic effect) and then detecting with light, the system adds a temporal and depth dimension to the imaging, allowing penetration beyond the optical diffusion limit while maintaining optical-resolution detection
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 non-contact, in vivo optical-resolution photoacoustic microscopy with improved signal-to-noise ratio and depth penetration, suitable for various clinical and pre-clinical applications, including imaging microvasculature and molecular targets.
Implementation Method 1
Photoacoustic imaging is an emerging hybrid imaging technology providing optical contrast with high spatial resolution. Nanosecond or picosecond laser pulses fired into tissue launch thermo-elastic-induced acoustic waves
Implementation Method 2
Nanosecond or picosecond laser pulses fired into tissue launch thermo-elastic-induced acoustic waves
Implementation Method 3
a photoacoustic remote sensing (PARS) system that uses co-focused excitation and interrogation lasers to detect pressure-induced refractive-index modulation subsurface
Data Source
AI summary
A photoacoustic remote sensing system (PARS) for imaging a subsurface structure in a sample, comprising one or more laser sources configured to generate a plurality of excitation beams configured to generate pressure signals in the sample at an excitation location, and a plurality of interrogation beams incident on the sample at the excitation location, a portion of the plurality of interrogation beams returning from the sample that is indicative of the generated pressure signals, an optical system configured to focus the plurality of excitation beams at a first focal point and the plurality of interrogation beams at a second focal point, the first and second focal points being below the surface of the sample, and a plurality of detectors each configured to detect a returning portion of at least one of the plurality of interrogation beams.