Beamforming for large-area scan and improved SNR in array-based photoacoustic microscopy

Area of Science:

• Biomedical Optics
• Medical Imaging
• Acoustic Microscopy

Background:

• Array-based photoacoustic microscopy (PAM) systems benefit from beamforming for large-area imaging.
• Optical-resolution PAM (OR-PAM) systems require efficient methods for enhanced performance.

Purpose of the Study:

• To quantify the imaging performance of a large field-of-view OR-PAM system utilizing a phased-array detector.
• To compare the effectiveness of different beamforming strategies on image quality.

Main Methods:

• A large field-of-view OR-PAM system was developed using a pulsed-laser diode and a 128-element linear ultrasound probe.
• Three beamforming strategies were evaluated: no beamforming, fixed focus beamforming, and dynamic focus delay-and-sum (DAS) beamforming.
• Signal-to-noise ratio (SNR) and generalized contrast-to-noise ratio (gCNR) were quantified.

Main Results:

• Dynamic focus DAS beamforming significantly increased and homogenized SNR across 1-cm² images, achieving up to 15 dB improvement over unfocused detection.
• DAS beamforming provided up to 30 dB improvement compared to out-of-focus regions in fixed focus configurations.
• Excellent target visibility (gCNR) was achieved with DAS beamforming on phantoms and ex vivo samples.

Conclusions:

• Dynamic focus DAS beamforming enhances SNR and target visibility in array-based OR-PAM.
• This beamforming strategy enables larger area scanning compared to single-element detector systems.
• The findings pave the way for advanced array-based PAM systems.