September 18, 2009

Acoustic Noise in MRI

Acoustic (Sound) Noise in MRI

  • One of the most disturbing obstacles for patients receiving an MRI particularly children and psychiatric patients
  • Interferes with communication between MRI technologists and patients
  • Interferes with functional MRI studies by producing unwanted stimulus. Noise may introduce changes in oxygenation in cortex and blood capillaries that may in turn affect signal receiving during fMRI.
  • They were anecdotal reports of temporary hearing loss related to MRI, but these have never been proven.
  • Depends on pulse sequence, types of scanner (coil structures and coil supports)
  • Average relative noise = 94-107 dB (in MRI bore) and 87-98 dB (in MR scanning room)
  • Noise from gradient recalled echo (GRE) sequences typically is louder than spin echo (SE) and echo planar imaging (EPI).
  • Main source: Lorentz forces acting on gradient coils and pulsing particularly two gradients along x- (frequency encode) and y- (phase encode) axes
  • Other sources: vibrations of conducting cryostat inner bore of MR machine due to eddy current, vibrations of radiofrequency body coil, etc (including several "unknown" pathways)

Image from

1. Cho ZH, Park SH, Kim JH, et al. Analysis of acoustic noise in MRI. Magn Reson Imaging 1997;15:815-822.
2. Edelstein WA, Hedeen RA, Mallozzi RP, et al. Making MRI quieter. Magn Reson Imaging 2002; 20:155-163.

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