On the accurate analysis of vibroacoustics in head insert gradient coils

Abstract

Purpose To accurately analyze vibroacoustics in MR head gradient coils. Theory A detailed theoretical model for gradient coil vibroacoustics, including the first description and modeling of Lorentz damping, is introduced and implemented in a multi-physics software package. Methods Numerical finite-element method simulations were used to establish a highly accurate vibroacoustic model in head gradient coils in detail, including the newly introduced Lorentz damping effect. Vibroacoustic coupling was examined through an additional modal analysis. Thorough experimental studies were used to validate simulations. Results Average experimental sound pressure levels (SPLs) and accelerations over the 0–3000Hz frequency range were 97.6dB, 98.7dB, and 95.4dB, as well as 20.6g, 8.7g, and 15.6g for the X-, Y-, and Z-gradients, respectively. A reasonable agreement between simulations and measurements was achieved. Vibroacoustic coupling showed a coupled resonance at 2300Hz for the Z-gradient that is responsible for a sharp peak and the highest SPL value in the acoustic spectrum. Conclusions We have developed and used more realistic multi-physics simulation methods to gain novel insights into the underlying concepts for vibroacoustics in head gradient coils, which will permit improved analyses of existing gradient coils and novel SPL reduction strategies for future gradient coil designs.

A high‐performance gradient insert for rapid and short‐T2 imaging at full duty cycle

“…The relatively high sound pressure levels measured in this study need careful attention but can be handled with appropriate hearing protection. Nevertheless, incorporating acoustic considerations into the gradient design is an interesting future option .…”

Eddy current nulled constrained optimization of isotropic diffusion encoding gradient waveforms

“…Although this work demonstrated the feasibility of simultaneously accounting for eddy currents and concomitant gradient effects in the diffusion waveform design, the concomitant field effects were not found to be significant for the protocol and hardware tested. The effects of concomitant fields are also expected to scale with maximum gradient amplitude, and the ability to compensate for these effects will become more valuable with the advent of faster and stronger gradients …”

“…The effects of concomitant fields are also expected to scale with maximum gradient amplitude, and the ability to compensate for these effects will become more valuable with the advent of faster and stronger gradients. [60][61][62]…”

Analysis of Influence of Coil Gradient System on Vibration Properties and Acoustic Noise Level Generated by the Low Field MRI Device

“…Three gradient fields for selection of slices of tested samples in three orthogonal Cartesian directions are created by the currents flowing in the conductors of the gradient coils. These currents in the presence of the static magnetic field result in large oscillating Lorentz forces and subsequent gradient coil conductor vibration giving rise to acoustic noise [2], [3]. The acoustic properties of the gradient system can be characterized by the frequency response function [4].…”

“…Recent scientific publications in this area have dealt with detailed modeling and simulation of gradient coils including theoretical description of Lorentz forces [3] and a phenomenon called Lorentz mechanical damping [6] for each of the turns of standard coils as well as of special coils used in the gradient system of the MRI device [7]. On the other hand, gradient coils can be modeled as one object [8].…”