Photoacoustic power azimuth spectrum for microvascular evaluation

Photoacoustics, 2021 · DOI: https://doi.org/10.1016/j.pacs.2021.100260 · Published: March 10, 2021

Simple Explanation

Blood vessels have complex structures that emit sound waves differently depending on the angle they are observed from. Analyzing these sound waves from a single angle is not enough to fully understand the vessel's characteristics. This paper introduces a new method called PA-PAS that maps the sound wave power across different angles. This reveals information about the vessel's direction and size. The study also uses a measurement called PWMF, which represents the main frequency of sound waves coming from the tissue, to determine the sizes of microvessels.

Study Duration

Not specified

Participants

Chick embryo model (n=6)

Evidence Level

Level 3; Experimental study

Key Findings

1
The intensity of photoacoustic signals from microvessels varies depending on the direction of measurement, with the strongest signals observed in the direction of the vessel's width.
2
The power-weighted mean frequency (PWMF) is inversely proportional to the size of the microvessel, meaning smaller vessels have higher PWMF values.
3
The PA-PAS method can differentiate between microvessel sizes, which was validated through simulations and experiments.

Research Summary

This study introduces a new method, PA-PAS, for evaluating microvessel structures by mapping the acoustic power spectrum of photoacoustic signals along the azimuth direction. The method calculates the spectral parameter power-weighted mean frequency (PWMF), demonstrating that microvessel information concentrates in the direction of its width, and PWMF decreases linearly with microvascular size. Experimental findings align with simulation results, confirming that PA-PAS can effectively differentiate microvessel sizes and has the ability of resisting low SNR than the traditional PACT method.

Practical Implications

Improved Microvascular Disease Diagnosis

The PA-PAS method offers a non-invasive way to diagnose microvascular diseases, which is less painful for patients compared to traditional methods like immunohistochemical staining.

Enhanced Tumor Angiogenesis Understanding

By quantitatively assessing changes in microvasculature size and density, PA-PAS can provide insights into tumor angiogenesis, aiding in cancer diagnosis and treatment.

Potential for In Vivo Microvascular Evaluation

The study demonstrates the feasibility of using PA-PAS for in vivo microvascular evaluation, opening avenues for real-time assessment of vascular structures in living organisms.

Study Limitations

1
The detection areas in this study contained vessels with relatively simple dendritic distributions and no complex vascular network was involved.
2
More experiments will be conducted to improve the robustness of the system.
3
Additional data will be used to derive the quantitative relationship between the PWMFs and vascular sizes by linear fitting of the PWMF values obtained at different vascular diameters.

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