Acoustic Noise
What adverse health effects are associated with MR scanner acoustic noise?
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Acoustic pressure in the human auditory range, dB(A), from various noise sources
As described in a prior Q&A, the vibration of gradient coils due to rapidly switched electrical currents produces sound waves during routine MR imaging. Some sequences (especially echo-planar imaging) generate sound pressures as high as 110-130 dB. In general, 3T scanners are noisier than those operating at 1.5T.
In addition to being painful, acoustic noise at the higher end of this range may cause temporary or permanent hearing loss. Even noise of lower intensity may cause anxiety or distress in patients, especially infants, young children, and the elderly. This may manifest as patient motion artifacts and degraded image quality.
In addition to being painful, acoustic noise at the higher end of this range may cause temporary or permanent hearing loss. Even noise of lower intensity may cause anxiety or distress in patients, especially infants, young children, and the elderly. This may manifest as patient motion artifacts and degraded image quality.
Short-term exposure to intense (100+ dB) noise may result in temporary threshold shifts (TTS), impaired hearing that typically lasts 15 minutes or less. However, some MR patients have experienced TTS with tinnitus lasting days or weeks.
More significant are permanent threshold shifts (PTS), typically caused by noise levels ≥ 130-140 dB. These result from disturbances in microcirculation to the organ of Corti with ischemic cell death. Children have a lower sensitivity for hearing damage, and restricting exposure to less than 120 dB is recommended.
More significant are permanent threshold shifts (PTS), typically caused by noise levels ≥ 130-140 dB. These result from disturbances in microcirculation to the organ of Corti with ischemic cell death. Children have a lower sensitivity for hearing damage, and restricting exposure to less than 120 dB is recommended.
At present there are no precisely agreed upon limits for sound exposure related to MRI. In the US, the Occupational Safety and Health Administration (OSHA) has defined permissible noise exposures for workers based on length of exposure. Applying these limits to typical MRI timeframes, noise exposures should not exceed 115 dB for 15 minutes of exposure down to 105 dB for 60 minutes. At no time should peak noise exposure exceed 140 dB. The UK limits are about 5 dB more stringent. In any case, there is unanimous agreement that ear protection should be offered to all patients (and accompanying family members) undergoing MRI examinations. The International Electrotechnical Commission (IEC) requires that ear protection should reduce exposure levels in MRI to below 99 dB. (Typical foam earplugs provide approximately 25 dB of noise reduction).
References
Frey AH. Human auditory system response to modulated electromagnetic energy. J App Physiol 1962; 17:689-692. (First description of RF hearing). [DOI Link]
International Electrotechnical Commission. IEC 60601-2-33:2010: Medical Electrical Equipment - Part 2-33: Particular Requirements for the Basic Safety and Essential Performance of Magnetic Resonance Equipment for Medical Diagnosis. 3rd ed. with amendments. International Electrotechnical Commission; 2015. (accessed July 2020)
McJury M. Shellock FG. Auditory noise associated with MR procedures: a review. J Magn Reson Imaging 2000; 12:37-45. [DOI Link]
National Electrical Manufacturers Association. NEMA Standards Publication MS 4-2010 Acoustic Noise Measurement Procedure for Diagnostic Magnetic Resonance Imaging Devices. 2010 (accessed July 2020) - describes details of performimg noise measurement
OSHA Standard 1910.95. Occupational noise exposure. Revised 12/12/08. (See Table G-16 for permissible occupational noise exposures)
Röschmann P. Human auditory system response to pulsed radio frequency energy in RF coils for magnetic resonance at 2.4 to 170 MHz. Magn Reson Med 1991; 21:197-215. [DOI Link] (RF hearing caused by MRI)
Frey AH. Human auditory system response to modulated electromagnetic energy. J App Physiol 1962; 17:689-692. (First description of RF hearing). [DOI Link]
International Electrotechnical Commission. IEC 60601-2-33:2010: Medical Electrical Equipment - Part 2-33: Particular Requirements for the Basic Safety and Essential Performance of Magnetic Resonance Equipment for Medical Diagnosis. 3rd ed. with amendments. International Electrotechnical Commission; 2015. (accessed July 2020)
McJury M. Shellock FG. Auditory noise associated with MR procedures: a review. J Magn Reson Imaging 2000; 12:37-45. [DOI Link]
National Electrical Manufacturers Association. NEMA Standards Publication MS 4-2010 Acoustic Noise Measurement Procedure for Diagnostic Magnetic Resonance Imaging Devices. 2010 (accessed July 2020) - describes details of performimg noise measurement
OSHA Standard 1910.95. Occupational noise exposure. Revised 12/12/08. (See Table G-16 for permissible occupational noise exposures)
Röschmann P. Human auditory system response to pulsed radio frequency energy in RF coils for magnetic resonance at 2.4 to 170 MHz. Magn Reson Med 1991; 21:197-215. [DOI Link] (RF hearing caused by MRI)
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What safety concerns relate to gradient fields?