Extending Imaging Depth in PLD-Based Photoacoustic Imaging: Moving Beyond Averaging

Area of Science:

• Biomedical Imaging
• Optical Physics
• Acoustics

Background:

• Pulsed laser diodes (PLDs) offer advantages for photoacoustic tomography (PAT) like portability and cost-effectiveness.
• PLD-based PAT systems typically have limited imaging depth compared to solid-state lasers due to lower pulse energy.
• Frame averaging is a common technique to enhance signal-to-noise ratio in high pulse repetition frequency (PRF) PLD systems.

Purpose of the Study:

• To investigate the feasibility of increasing depth sensitivity in PLD-based PAT systems.
• To evaluate the combined effect of sub-pitch translation and frame averaging on imaging depth.
• To optimize PLD-based PAT for improved performance.

Main Methods:

• Implemented sub-pitch translation on the receive-side ultrasound transducer.
• Combined sub-pitch translation with frame averaging techniques.
• Conducted experiments on phantoms with diluted India ink targets at varying laser energy levels (21 µJ and 27 µJ).

Main Results:

• Achieved an approximate 38.5% improvement in imaging depth (9.1 to 12.6 mm) at 21 µJ using λ/4-pitch translation and 128-frame averaging.
• Observed a ~33.3% increase in imaging depth (10.8 to 14.4 mm) at 27 µJ with λ/4-pitch translation and 128-frame averaging.
• Noted a reduction in achievable frame rate by factors of 2 and 4 for λ/2 and λ/4 sub-pitch translation, respectively.

Conclusions:

• Combining sub-pitch translation with frame averaging significantly enhances depth sensitivity in PLD-based PAT.
• The developed method offers a viable approach to overcome depth limitations in portable PLD-based PAT systems.
• Trade-offs exist between improved imaging depth and reduced frame rates, requiring careful consideration for specific applications.