Vibro-magnetometry: Theoretical aspects and simulations

Abstract

In this article, we introduce the theory for vibro-magnetometry (VM) with computational simulations for an idealized experimental setup. A method based on acoustic radiation force and magnetic measurement has been proposed for interrogating the mechanical vibrations of a target immersed in fluid medium. In this method, ultrasound radiation is used to exert a low-frequency (in kHz range) force on a rigid magnetized target immersed in a viscoelastic medium. In response, the target vibrates sinusoidally in a pattern determined by viscoelastic properties of the medium. The magnetic field resulting from target vibration is related to both the ultrasonic and low-frequency (kHz range) mechanical characteristics of the medium. We report the relationship between the magnetic field signal and the incident ultrasonic pressure field in terms of the mechanical parameters of the medium. Simulations were conducted to demonstrate a simple approach based on using amplitude-modulated ultrasound to generate a dynamic acoustic radiation force on a magnetic target. The magnetic field generated by vibration of this target is then obtained and used to estimate the radiation-force-induced displacement as a function of time. It was observed that the intensity of the dynamic component of the magnetic field caused by the acoustic excitation is high enough to be registered by a conventional magnetic sensor. When a low stress is applied on a reactive magnetic target embedded in the medium, the subsequent oscillating magnetic field is measured by a dedicated magnetic sensor, yielding the applicable mechanical information of the host medium. The proposed methodology presents a powerful tool for evaluation of acoustic radiation force as well as the mechanical properties of soft materials.

Dynamic radiation force of acoustic waves on absorbing spheres

“…In this case, the induced vibration on the object is measured by a laser vibrometer. Properties of magnetic objects can be probed by measuring the induced oscillatory magnetic field with a sensitive magnetic detector [5]. Vibroacoustography technique has motivated the author to investigate how dynamic radiation force acts on viscoelastic objects.…”

Estudos de técnicas ultrassônicas para análise de propriedades mecânicas de meios viscoelásticos

“…Vibromagnetometry, introduced by Carneiro et al [47], is a technique based on acoustic excitation of a magnetized target and magnetic measurement of the induced displacement. In their introductory work, the authors discussed theoretical aspects of the oscillatory movement of a rigid sphere, embedded in viscous and visco-elastic media, displaced by dynamic acoustic radiation force with frequency range of 0-0.5 MHz.…”

“…Carneiro et al [47] proposed the magnetic tracking of the displacement of a magnetic target induced by dynamic acoustic radiation force between 0 and 0.5 MHz [49]. Based on Oestreicher's theory [48], they simulated a magnetic-sensor response due to the vibration of a spherical magnet embedded in water and in a viscoelastic medium.…”

Imagens das propriedades viscoelásticas por ressonância magnética e ultrassom

“…Carneiro e colaboradores [45] vêm aplicando força de radiação acústica e magnética para vibrar um meio marcado com partículas magnéticas, e usando transdutores ultrassônicos e magnéticos, medir os deslocamentos resultantes das vibrações. Essas técnicas de medidas foram denominadas por eles de Vibro-magnetometria (VM) e Magnetoacustografia (MA), as quais têm potencial para serem empregadas em estudos de meios ou tecidos, onde marcadores ou alvos magnéticos estão presentes [46].…”