Bessel and conical beams and approximation with annular arrays

Area of Science:

• Acoustics
• Wave physics
• Medical imaging technology

Background:

• Limited-diffraction beams offer advantages over traditional wave propagation.
• Bessel beams are a novel class of beams with reduced diffraction.
• Conical transducers provide an approximate limited-diffraction solution but have near-field limitations.

Purpose of the Study:

• To compare the performance of Bessel beams with conical transducers for limited-diffraction applications.
• To evaluate the suitability of Bessel beams for hybrid ultrasound systems.
• To demonstrate the excitation and characteristics of a zero-order Bessel beam using annular transducers.

Main Methods:

• Simulated the acoustic fields of Bessel beams and compared them with those of conical transducers.
• Investigated the excitation of a zero-order Bessel beam using an annular transducer with equal-area element division and fixed prefocus.
• Analyzed beamwidth, depth of field, and steerability characteristics.

Main Results:

• The Bessel beam exhibited a narrower beamwidth and less deviation in the near-field compared to the conical transducer.
• The Bessel beam demonstrated a larger depth of field than unfocused transducers.
• Simulations showed favorable comparisons of the approximate Bessel beam against fixed-focus, unfocused, and conical transducer beams.

Conclusions:

• Bessel beams are a more effective limited-diffraction solution than conical transducers, particularly for hybrid transmission-reception systems.
• Zero-order Bessel beams can be practically excited using conventional annular transducer arrays with appropriate design parameters.
• The Bessel beam's characteristics make it advantageous for applications requiring extended range and precise focusing in medical ultrasound.