MRI acoustic noise: Sound pressure and frequency analysis

Counter, S. Allen; Olofsson, Åke; Grahn, Hans; Borg, Erik

doi:10.1002/jmri.1880070327

Cited by 105 publications

(76 citation statements)

References 8 publications

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“…The frequency characteristics of this noise are altered by the gradient waveform deˆned by the pulse sequence design and imaging parameters such as slice thickness, direction of the imaging plane axis,ˆeld of view (FOV), repetition time (TR), and echo time (TE). [20][21][22] The structural features of the gradient unit, such as special sound insulation, and the material and construction of the coil circuit and support structures, also aŠect the transmission and propagation of acoustic noise. 13,[17][18][19]23,24 Technologies to reduce MR scanning sound Developments to reduce the acoustic noise of MR systems have been carried out in both hard-ware development of the gradient magneticˆeld system and pulse sequence techniques.…”

Section: Discussionmentioning

confidence: 99%

“…18,20,[30][31][32] A commercially available noise-level measuring system including a microphone, a pre-ampliˆer to improve SNR and avoid electromagnetic interference, a sound generating system for calibration, and an analyzer to compute the sound level of MR has been used. 9,18,21,22,33 Several reports systematically evaluating MR scanning noise were published when fast imaging using gradient echo techniques were released. 12,20 The maximum noise levels in these reports were 93 dB (A) 20 or 103 dB (A).…”

Section: Measuring the Acoustic Noise Of Mr Scannersmentioning

confidence: 99%

“…12 Further investigations were conducted when FSE and EPI became available. 14,30 The following sound pressure levels (SPL) have been reported; 100 dB (A) (Turbo Spin Echo), 30 113 dB (A) (Fast Gradient Echo), 22 118 dB (A) (EPI), 17 138 dB (EPI), 31 118 dB (A) (EPI), 32 and 132 dB (A) (EPI). 33 As a guide for the manufacture of MR scanners, 140 dB (peak) maximum limitation of acoustic noise by an MR system deˆned by IEC60601-2-33 34 and the reporting standard dened by NEMA MS-4 35 are recommended in thè guidance for the submission of premarket notiˆca-tions for magnetic resonance diagnostic devices' released by the Center for Devices and Radiological Health.…”

Section: Measuring the Acoustic Noise Of Mr Scannersmentioning

confidence: 99%

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A Survey Analysis of Acoustic Trauma Related to MR Scans

et al. 2012

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Purpose: The maximum limit of MR scanner noise and necessity of ear protection is dened in the IEC standard (IEC60601-2-33) of MR safety. With improvements in MR scanner performance, pulse sequences generating higher scanning noise have been used clinically. In this study, we investigated the factors signiˆcantly related to potential acoustic trauma cases (PATC) after MR examinations. To consider the future direction for MR safety and prevention of acoustic trauma, issues related to noise generation by MR scanners and acoustic trauma were systematically reviewed.Methods: A statistical analysis was performed using the data set from a survey (n＝974) conducted in 2010 by the JSMRM safety committee. Hierarchical clustering analysis was used to extract the characteristics of the responders. With this classiˆcation as a reference, tests of independence and a residual analysis were employed to evaluate the factors related to PATC.Results: No signiˆcant relationship was observed between the ear protection policy and the incidence or the reported outcome of PATC. While the two main clusters out of the six clusters extracted were associated with who reported the PATC and the conˆrmation process of the acoustic noise level of MR scanners, no cluster was associated with the frequency of PATC. An absence of PATC was signiˆcantly less reported (p＝0.03) and more PATC was reported (p＝0.04) by facilities with 3T MR systems.Discussion: Although the total frequency was 4 cases, it should be noted that persistent hearing disturbances are a possible consequence of MR examinations. Neither the condition of the subjects nor the ear protection method was signiˆcantly related to the probability of PATC, suggesting the di‹culty of predicting the potential risk of acoustic trauma. It is recommended to more systematically follow up PATC cases and clarify the risk factors.

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Section: Discussionmentioning

confidence: 99%

Section: Measuring the Acoustic Noise Of Mr Scannersmentioning

confidence: 99%

Section: Measuring the Acoustic Noise Of Mr Scannersmentioning

confidence: 99%

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A Survey Analysis of Acoustic Trauma Related to MR Scans

et al. 2012

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“…However, the generation of magnetic field gradients requires time-varying currents which, in the presence of a strong external magnetic field, can lead to a number of unwanted effects like eddy currents (1-3), gradient coil vibrations (4) and acoustic noise (5)(6)(7). Eddy currents are a manifestation of Faraday's law of induction in which a time-varying magnetic field will induce a current in any nearby conducting structure, like the cryostat.…”

Section: Introductionmentioning

confidence: 99%

Compensation of gradient-induced magnetic field perturbations

Nixon

McIntyre

Rothman

et al. 2008

Journal of Magnetic Resonance

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Pulsed magnetic field gradients are essential for MR imaging and localized spectroscopy applications. However, besides the desired linear field gradients, pulsed currents in a strong external magnetic field also generate unwanted effects like eddy currents, gradient coil vibrations and acoustic noise. While the temporal magnetic field perturbations associated with eddy currents lead to spectral line shape distortions and signal loss, the vibration-related modulations lead to anti-symmetrical sidebands of any large signal (i.e. water), thereby obliterating the signals from smaller signals (i.e. metabolites). Here the measurement, characterization and compensation of vibrations-related magnetic field perturbations is presented. Following a quantitative evaluation of the various temporal components of the main magnetic field, a digital B 0 magnetic field waveform is generated which reduces all temporal variations of the main magnetic field to within the spectral noise level.

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“…For example, since the imaging process is accompanied by the gradient coil current switching on and off, varying Lorentz force is produced on the coil structure, under a strong static magnetic field environment. The varying Lorentz force propels the gradient assembly to vibrate, thus emitting loud acoustic noise [8]. The vibration of the gradient assembly can also transmit to other joint components in the MRI scanner.…”

Section: From Gradient Coil Design To Acoustic Noise Controlmentioning

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 acoustic noise: Sound pressure and frequency analysis

Cited by 105 publications

References 8 publications

A Survey Analysis of Acoustic Trauma Related to MR Scans

A Survey Analysis of Acoustic Trauma Related to MR Scans

Compensation of gradient-induced magnetic field perturbations

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

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