Pulsed photoacoustic flow imaging with a handheld system

Area of Science:

• Biomedical Optics
• Medical Imaging
• Fluid Dynamics

Background:

• Accurate blood flow estimation is crucial for diagnosing various diseases.
• Traditional flow imaging techniques struggle with low flow speeds and near-vessel wall detection.
• Photoacoustic imaging offers reduced background tissue contamination, making it suitable for flow studies.

Purpose of the Study:

• To develop and evaluate a handheld, portable photoacoustic system for flow imaging.
• To assess the system's capability for high-speed, quantitative flow velocity measurements.
• To investigate the performance of photoacoustic flow imaging in different optical environments.

Main Methods:

• Utilized a clinical, handheld photoacoustic system with a 7.5 MHz linear array and a high-repetition-rate diode laser.
• Performed in vitro flow imaging experiments using microparticles in a transparent medium and tissue-mimicking phantom.
• Acquired two-dimensional (2-D) flow images and calculated quantitative flow velocities.

Main Results:

• Successfully obtained 2-D flow images and quantitative velocities ranging from 12 to 75 mm/s.
• Achieved low flow estimation errors of approximately 7% in a transparent medium.
• Observed increased error (up to 40%) in tissue-realistic scattering conditions due to signal-to-noise ratio limitations.

Conclusions:

• The developed portable photoacoustic system demonstrates effective in vitro flow imaging capabilities.
• The system provides quantitative flow velocity measurements, though scattering affects accuracy.
• Future advancements may enable in vivo photoacoustic flow imaging using novel contrast agents or improved setups.