Pulsed photoacoustic Doppler flowmetry using time-domain cross-correlation: accuracy, resolution and scalability

Area of Science:

• Biomedical Optics
• Ultrasound Imaging
• Fluid Dynamics

Background:

• Accurate measurement of blood velocity is crucial for diagnosing vascular diseases.
• Existing techniques face limitations in spatial resolution and applicability to microcirculation.

Purpose of the Study:

• To investigate the feasibility of pulsed photoacoustic Doppler for spatially resolved blood velocity measurements.
• To assess the accuracy and resolution of this technique in a blood-simulating phantom.

Main Methods:

• Utilized a pulsed photoacoustic Doppler technique in acoustic resolution mode.
• Quantified Doppler time shifts via cross-correlation of photoacoustic waveform pairs.
• Employed a blood-simulating phantom with absorbers moving at known velocities, detected by PZT ultrasound transducers (20, 5, and 3.5 MHz).

Main Results:

• Achieved velocity quantification in the range of ±0.15 to ±1.5 ms(-1) with accuracies as low as 1%.
• Demonstrated a measurement resolution of <4% of the measured velocity below the maximum measurable velocity (|V(max)|).
• Showed that resolution and |V(max)| can be scaled for microvasculature velocities (< 50 mms(-1)).

Conclusions:

• Pulsed photoacoustic Doppler is a feasible technique for spatially resolved blood velocity measurements.
• The method offers high accuracy and resolution, suitable for microcirculation studies.
• This technique provides a prospect for mapping flow within the microcirculation.