Breaking the resolution limit in photoacoustic imaging using non-negativity and sparsity

Area of Science:

• Biomedical Optics
• Acoustic Imaging
• Thermodynamics

Background:

• Spatial resolution in photoacoustic imaging degrades with depth due to acoustic wave attenuation.
• Thermodynamic principles, specifically entropy increase from scattering and dissipation, limit ultimate resolution.
• Blurring of deep structures necessitates advanced compensation techniques.

Purpose of the Study:

• To develop and demonstrate a numerical method for compensating acoustic attenuation in photoacoustic imaging.
• To enhance spatial resolution for structures embedded in attenuating media.
• To validate the method using experimental data from fat tissue.

Main Methods:

• Utilized experimental data of 1D acoustic waves optically induced by nanosecond laser pulses in fat tissue.
• Applied a two-step reconstruction process: 1D attenuation compensation followed by standard ultrasound reconstruction.
• Employed non-negativity and sparsity constraints to invert frequency-dependent acoustic attenuation.

Main Results:

• Achieved a twofold improvement in spatial resolution for imaging through 20 mm of porcine fat tissue.
• Successfully compensated for acoustic wave attenuation, improving image clarity for deeper structures.
• Demonstrated the method's applicability to 2D and 3D photoacoustic imaging in attenuating media.

Conclusions:

• Numerical compensation of acoustic attenuation significantly enhances spatial resolution in photoacoustic imaging.
• The proposed method is effective for imaging through scattering and dissipative biological tissues.
• This approach offers a pathway to overcome fundamental resolution limits in deep-tissue photoacoustic imaging.