Non-Interferometric Photoacoustic Remote Sensing for Subsurface Imaging
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Solution Overview
Problem
Current photoacoustic imaging technologies face challenges in achieving non-contact, in vivo imaging with optical resolution due to the need for physical contact or ultrasound coupling agents, and existing non-contact methods suffer from poor signal-to-noise ratio and limited depth penetration.
Innovation Solution
The non-interferometric photoacoustic remote sensing (NI-PARS) system uses a pulsed excitation beam co-focused with a co-scanned interrogation beam to detect pressure-induced refractive-index modulation, eliminating phase-sensitivity and enabling high signal-to-noise ratio detection of subsurface structures without the need for ultrasound coupling agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If interferometric methods are used to detect surface oscillations, then sensitivity to scattered probe beam phase modulations is improved, but the system becomes sensitive to unwanted vibrations and complex amplitude reflectivity modulations, worsening the signal-to-noise ratio
Solution Approach 1:
The patent extracts and eliminates the interferometric detection component from the system. By using direct detection of photoacoustic signals instead of interferometric methods, the system removes sensitivity to phase modulations and unwanted vibrations while maintaining detection capability for pressure-induced refractive index changes.
Solution Approach 2:
The patent replaces the mechanical/optical interferometric detection system with a direct photoacoustic detection system. Instead of using interferometry to detect surface oscillations, the system directly detects acoustic waves generated by photoacoustic effect, substituting a more robust detection mechanism that is insensitive to vibrations and phase modulations.
2Measurement precision
If piezoelectric transducers with ultrasound coupling medium are used, then photoacoustic signal detection is achieved, but physical contact and coupling are required, which is undesirable for clinical applications such as wound healing and endoscopic procedures
Solution Approach 1:
The patent replaces the mechanical contact-based piezoelectric transducer system with an optical detection system. By using photoacoustic microscopy with optical detection, the system eliminates the need for ultrasound coupling gels and physical contact, enabling non-contact imaging suitable for wound healing and endoscopic applications.
Solution Approach 2:
The patent introduces light as an intermediary medium to detect photoacoustic signals without physical contact. Instead of using ultrasound waves that require coupling media, the system uses optical detection of pressure-induced refractive index changes, allowing non-contact imaging while maintaining detection sensitivity.
3Manufacturing precision
If optical resolution photoacoustic microscopy is used to achieve micron-scale resolution, then penetration depth is limited to approximately 1 mm due to fundamental limitations of light transport
Solution Approach 1:
The patent segments the imaging problem into two distinct functions: optical excitation for resolution and acoustic detection for depth penetration. By using optical excitation beams to generate photoacoustic signals and acoustic waves for detection, the system achieves both micron-scale resolution from optical focusing and deep penetration from acoustic wave propagation.
Solution Approach 2:
The patent changes the detection parameter from direct optical detection to acoustic wave detection. By detecting photoacoustic signals generated by optical absorption, the system overcomes the fundamental limitation of light transport while maintaining optical resolution, enabling deep tissue imaging with micron-scale precision.
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
NI-PARS achieves real-time, high-resolution, non-contact imaging of subsurface structures with improved signal-to-noise ratio and optical resolution, suitable for clinical and pre-clinical applications, including imaging of microvasculature and blood oxygen saturation without the limitations of previous methods.
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
an optical system that focuses the excitation beam at a first focal point and the interrogation beam at a second focal point, the first and second focal points being below the surface of the sample
Implementation Method 3
detect pressure-induced refractive-index modulation, eliminating phase-sensitivity and enabling high signal-to-noise ratio detection of subsurface structures
Data Source
AI summary
A photoacoustic remote sensing system (NI-PARS) for imaging a subsurface structure in a sample, has an excitation beam configured to generate ultrasonic signals in the sample at an excitation location; an interrogation beam incident on the sample at the excitation location, a portion of the interrogation beam returning from the sample that is indicative of the generated ultrasonic signals; an optical system that focuses at least one of the excitation beam and the interrogation beam with a focal point that is below the surface of the sample; and a detector that detects the returning portion of the interrogation beam.