Composite Orbital Angular Momentum for Super-resolution Ultrasound Imaging

Area of Science:

• Acoustics
• Wave Physics
• Biomedical Imaging

Background:

• Acoustic imaging resolution is limited by diffraction, hindering applications in biomedicine and nondestructive testing.
• Existing super-resolution techniques involve trade-offs in efficiency, invasiveness, complexity, and scalability.

Purpose of the Study:

• To develop a far-field super-resolution ultrasound imaging strategy.
• To overcome the fundamental spatial resolution limitations imposed by acoustic diffraction.

Main Methods:

• Utilizing composite orbital angular momentum (OAM) by synthesizing vortex beams with multiple topological charges.
• Converging the collective angular spectrum to a Dirac delta function to recover high spatial frequencies from scattered fields.

Main Results:

• Achieved subdiffraction imaging with resolutions down to 0.2λ (simulation) and 0.24λ (experiment) at 1 MHz.
• Demonstrated robust imaging of metallic wires, steel structures, and blood vessels.
• Enabled functional imaging capabilities, including chirality discrimination.

Conclusions:

• Composite OAM offers a powerful new approach for enhancing ultrasound imaging resolution.
• This method surpasses the Rayleigh limit and traditional trade-offs.
• OAM provides a new degree of freedom for advanced ultrasound applications.