MRI Gradient Coil Cylinder Sound Field Simulation and Measurement

Mechefske, Chris K.; Wu, Yuhua; Rutt, Brian K.

doi:10.1115/1.1488169

Cited by 20 publications

(22 citation statements)

References 8 publications

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“…The variability of the SPL along the centerline is particularly dramatic with two quiet zones at about 10 cm and Ϫ20 cm from the isocenter. These patterns are consistent with previous results (13,14 ). These two quiet zones along the centerline are more prominent in the simulation than in the measurement results, likely due again to the slight oversimplification of the model, the environment effects being ignored, and the fact that the real acoustic field is considerably more complicated than the simulated result.…”

Section: Vibro-acoustic Noise Simulation and Measurementsupporting

confidence: 92%

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Modal analysis and acoustic noise characterization of a 4T MRI gradient coil insert

Mechefske

Yao

et al. 2004

Concepts Magn Reson

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High magnetic field strength and high-speed gradient coil current switching are combining to yield high acoustic sound pressure levels (SPL) in and around magnetic resonance imaging (MRI) scanners. Studies have already been conducted that partially characterize this sound field, and various methods have been investigated in an attempt to attenuate the noise generated. To more fully characterize and predict the vibration and acoustic response of a gradient coil inside a scanner, a series of finite element analysis (FEA), vibro-acoustic analysis, and experimental measurements were carried out. The FEA and vibro-acoustic model used was based on specific internal and external structural dimensions and the material physical properties of a gradient coil insert. The model-based results were verified through experimental vibration and acoustic testing of the same gradient coil. It was found that the experimental analysis results were in good agreement with the model-based results in all cases. The numerical methods developed in this study could provide a basis for the virtual testing of gradient coil designs that will allow the prediction of vibration and acoustic behavior.

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Section: Vibro-acoustic Noise Simulation and Measurementsupporting

confidence: 92%

“…With the knowledge of the coil conductor pattern, electric current, and magnetic field strength, the Lorentz forces produced by each small current carrying element can be determined. The force experienced by a current carrying element, dl, due to the magnetic induction, B, is (14,20):…”

Section: Vibro-acoustic Noise Simulationmentioning

confidence: 99%

Modal analysis and acoustic noise characterization of a 4T MRI gradient coil insert

Mechefske

Yao

et al. 2004

Concepts Magn Reson

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“…A number of works have also been published which focus on the analysis of superconducting solenoids [168], as well as on full MRI scanners [154,51] and also consider the structural design of higher field scanners [64]. Acoustic effects in MRI scanners have also been investigated [224,173], with attempts to design noise reduction systems [252,253,208] and even analyse the acoustic effects in the human head [156]. Others have attempted to model these complex physical effects to aid the design of the MRI magnetic coils [101,210], to analyse the plane strain effects on superconducting solenoids [168] and the effects of the magnetic field exposure on the patient [63].…”

Section: Applications To Mri Scannersmentioning

confidence: 99%

A High Order Finite Element Coupled Multi-Physics Approach To MRI Scanner Design

Bagwell¹

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“…The temperature-caused material property variation was not considered in the simulation. For the model establishment, the element size was controlled to be less than 1/6 of the smallest wave acoustic wave length [116]. Harmonic analysis was used here from 100 Hz to 3000…”

Section: ν τ Xzmentioning

confidence: 99%

“…Infinite acoustic boundary condition was applied on the outer surface of the surrounding air, implying that the acoustic wave was totally absorbed here with no reflection [139]. The cryostat was set to be simply supported [116]. Since the load distribution of the different coils has symmetric or anti-symmetric features, 1/8 model can be used to simulate the scanner as a whole.…”

Section: Fem Acoustic Model Of a Conventional Mri Scannermentioning

confidence: 99%

Gradient coil design and acoustic noise control in magnetic resonance imaging systems

Wang¹

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In magnetic resonance imaging (MRI), three-dimensional linearly varied magnetic field gradients are required in the imaging volume, for the encoding of the spatial information of the imaged object.The gradient magnetic field is generated by gradient coils, whose performance directly affects the final MR image quality. Modern MRI applications demand gradient coils to be designed with higher performance such as a faster slew rate for rapid imaging, and fewer system interactions to ensure distortion-free images.During MR imaging, the gradient coil current switches quickly and the alternating current under a strong magnetic field generates a large Lorentz force, thus increasing the vibrations and noise in the gradient assembly, and the vibrations can also transmit to other components in the system. Moreover, the gradient magnetic field induces eddy currents on the surrounding conductive materials, resulting in further mechanical vibration. The sound pressure level (SPL) of an MRI scanner very commonly exceeds 100 dB, which may be discomforting to patients. Therefore, an effective acoustic noise control is necessary for the MRI operation.This thesis attempts to design a novel gradient coil system in an MRI scanner with a particular focus on the investigation of an acoustic noise control scheme. A brief summary of the thesis work is as follows.(1) Gradient coil design A conventional cylindrical MRI scanner has a long patient bore, which may make some patients uneasy due to claustrophobia. In order to alleviate this, an asymmetric gradient coil was proposed to accommodate an asymmetric MRI magnet. The coil was designed with a number of features, for example, to enable the installation of the shim tray, the coil was configured with one end connected and the other end separated. The electromagnetic and acoustic performances were also improved compared with a conventional non-connected coil system.The stream function approach is commonly used in gradient coil design, but an issue with this design is a connection problem between coil loops. To eliminate the field errors due to the coil connections, this thesis proposed a novel spiral coil design scheme, including both transverse coils and a longitudinal coil. The proposed coil design method was not only able to improve the magnetic II performance of the coil, but also could integrate the cooling system into the coil design using hollow wires in the discrete wire space.Wire spacing is a major engineering problem in gradient coil design. Conventional gradient coils are designed with three primary layers and three shielding layers, and in general, primary transverse coils are located in two layers separated by a very dense wire structure. In this thesis, a novel gradient coil design strategy using a layer-sharing scheme was proposed. This design scheme mutually combined the x and y gradient coil layers, effectively utilizing the unoccupied or sparse coil-layer space. The new method was modelled in the case of an asymmetric head coil design, and enhanced coil performan...

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MRI Gradient Coil Cylinder Sound Field Simulation and Measurement

Cited by 20 publications

References 8 publications

Modal analysis and acoustic noise characterization of a 4T MRI gradient coil insert

Modal analysis and acoustic noise characterization of a 4T MRI gradient coil insert

A High Order Finite Element Coupled Multi-Physics Approach To MRI Scanner Design

Gradient coil design and acoustic noise control in magnetic resonance imaging systems

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