Acoustic analysis of gradient-coil noise in MR imaging.

Abstract

A survey was conducted of acoustic noise levels in magnetic resonance (MR) imaging systems. Static magnetic flux and radio-frequency pulses did not affect the function of shielded sound-pressure detection equipment. Noise levels were measured at bore isocenter during a variety of imaging sequences in six MR imaging systems with magnetic fields of 0.35-1.5 T. Measured noise ranged from 82 to 93 dB on the A-weighted scale and from 84 to 103 dB on the linear scale. Noise levels increased during sequences employing thinner section thickness and shorter repetition and echo times and were independent of field strength. Gradient-coil noise in MR imaging is an annoyance but is well within safety guidelines.

Auditory Noise Associated With MR Procedures: A Review

“…Hurwitz et al (13) reported that the sound levels varied from 82 to 93 dB on the A-weighted scale and from 84 to 103 dB on the linear scale (13). The report concluded that gradient magnetic field-induced noise was an annoyance but well within recognized safety guidelines (13).…”

“…The gradient magnetic field is the primary source of acoustic noise associated with MR procedures (12)(13)(14)(15)(16)(17)(18)(19)(20). This noise occurs during the rapid alterations of currents within the gradient coils.…”

Sound-Level Measurements and Calculations of Safe Noise Dosage During EPI at 3 T

“…Potentially, measurements could reflect not only airborne sound, but also electrical signals induced by the time-varying magnetic fields of the scanner and by movements of the leads within static magnetic fields. To circumvent this problem, some researchers have adopted additional electromagnetic shielding of the microphone and amplification of its signal to measure levels with adequate sensitivity and accuracy (4,12,13). The method we describe has the advantage of not requiring additional electromagnetic shielding or amplification, as it uses a relatively sensitive microphone (47 mV/Pa) to give an acceptable signal-to-noise ratio in the measuring equipment and cables.…”

Quiet PROPELLER MRI Techniques Match the Quality of Conventional PROPELLER Brain Imaging Techniques

“…Noise tends to be enhanced by decreases in section thickness, FOV, TR, and TE. 5 Noise levels for clinical MR imaging pulse sequences run as high as 100 -120 dB, [19][20][21][22] levels capable of causing temporary or even permanent hearing loss if hearing protection is not properly applied.…”