Spatio-temporal ultrasound beam modulation to sequentially achieve multiple foci with a single planar monofocal lens

José Miguel Fuster,Pilar Candelas,Sergio Pérez-López

doi:10.1038/s41598-021-92849-x

Abstract

Ultrasound focusing is a hot topic due to its multiple applications in many fields, including biomedical imaging, thermal ablation of cancerous tissues, and non destructive testing in industrial environments. In such applications, the ability to control the focal distance of the ultrasound device in real-time is a key advantage over conventional devices with fixed focal parameters. Here, we present a method to achieve multiple time-modulated ultrasound foci using a single planar monofocal Fresnel Zone Plate. The method takes advantage of the focal distance linear dependence on the operating frequency of this kind of lenses to design a sequence of contiguous modulated rectangular pulses that achieve different focal distances and intensities as a function of time. Both numerical simulations and experimental results are presented, demonstrating the feasibility and potential of this technique.

Highlights

Ultrasound focusing is a hot topic due to its multiple applications in many fields, including biomedical imaging, thermal ablation of cancerous tissues, and non destructive testing in industrial environments
We present a spatio-temporal beam modulation technique to achieve multiple foci using a conventional Fresnel Zone Plate (FZP)
One intrinsic property of FZPs is that they are designed to operate at a single frequency, as the different radii of the lens depend on the central design wavelength

Summary

Introduction

Ultrasound focusing is a hot topic due to its multiple applications in many fields, including biomedical imaging, thermal ablation of cancerous tissues, and non destructive testing in industrial environments In such applications, the ability to control the focal distance of the ultrasound device in real-time is a key advantage over conventional devices with fixed focal parameters. The method takes advantage of the focal distance linear dependence on the operating frequency of this kind of lenses to design a sequence of contiguous modulated rectangular pulses that achieve different focal distances and intensities as a function of time. Both numerical simulations and experimental results are presented, demonstrating the feasibility and potential of this technique. This π phase change results in a propagation path difference of /2 between consecutive radii, which directly yields to the design equation of the lens:

Methods

Results

Conclusion