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).

Etiology

• 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 www.noise-busters.com

References:

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.