A multi-aperture encoding scheme for increased SNR in photoacoustic Imaging

Area of Science:

• Biomedical optics
• Medical imaging
• Acoustic engineering

Background:

• Photoacoustic imaging (PAI) offers non-invasive visualization of internal body structures and tissue morphology.
• Multi-aperture PAI (MP-PAI) improves resolution, contrast, and field of view over conventional PAI.
• Existing MP-PAI systems using capacitive micromachined ultrasound transducers (CMUTs) with shared channels face limitations in signal-to-noise ratio (SNR).

Purpose of the Study:

• To introduce and validate a multi-aperture encoding scheme (MAES) for enhancing SNR in MP-PAI systems.
• To develop an analytical model for calculating SNR with arbitrary encoding sequences in MAES.
• To compare the performance of MAES against conventional MP-PAI through simulations and experiments.

Main Methods:

• Implementing MAES involving simultaneous signal reception from multiple CMUTs using an encoding matrix.
• Recovering superimposed signals from shared channels by applying a decoding matrix.
• Validating the analytical SNR model and MAES performance using numerical simulations and experimental studies with bipolar and unipolar encoding sequences.

Main Results:

• Numerical simulations indicate MAES achieves an SNR gain of 5.8 dB (S-sequence) and 8.8 dB (truncated Hadamard) with 15 transducers compared to conventional MP-PAI.
• Experimental results with three transducers using S-sequences demonstrated a 1.5 dB SNR improvement over conventional MP-PAI.
• The experimental findings align well with the predictions of the analytical SNR model.

Conclusions:

• MAES effectively increases SNR in multi-aperture photoacoustic imaging systems.
• The proposed encoding scheme offers a significant improvement for non-invasive medical imaging applications.
• MAES provides a viable strategy to overcome SNR limitations in current MP-PAI technologies.