Aims and objectives
Acoustic noise during magnetic resonance imaging (MRI) scan can not only cause anxiety,
stress,
and annoyance but also cause a temporary or permanent shift in the hearing threshold [1].
Studies have described that this sound affects the results of functional MRI [2].
In addition,
the noise interferes with verbal communication and pediatric imaging.
The noise is primarily caused by Lorenz forces (F) induced in the scanner while electric currents (I) are switched in the gradient coils within the static magnetic field (B0) (figure 1).
Acoustic...
Methods and materials
We measured sound pressure levels induced by gradient impulses in a 3.0-T superconducting MRI system (Signa Excite HDxt,
General Electric Healthcare,
Wisconsin,
USA) and a 0.4-T permanent magnet open MRI system (APERTO Eterna,
Hitachi medical corporation,
Tokyo,
Japan) (figure 2).
Measurements were performed using a precision integrating sound level meter (ISLM)(NL-18,
RION Co.,
Ltd.,
Tokyo,
Japan) connected to an electret condenser microphone.
The measurement positions inside the bore in both the systems were 143 and 75 points,
respectively (figure 3).
A simple trapezoidal pulse was...
Results
The acoustic noise magnitude induced by the gradient impulse varied from 93.5 dB to 116.4 dB (3.0 T) and from 76.9 dB to 103.6 dB (0.4 T),
according to the measurement positions.
Figure 8 shows the spatial distribution of GPAN-TFs of X,
Y,
and Z gradient coils in a superconducting MRI (3.0 T).
GPAN-TF of the X coil reached its peak at ±X sides from the isocenter (figure 9).
GPAN-TF of the Y coil had a maximum value at a higher position than the isocenter...
Conclusion
Multipoint analysis using GPAN-TFs facilitates detailed evaluation of the spatial dependence of acoustic noise among different MRI systems.
References
[1] McJury M,
Shellock F.
Auditory noise associated with MR procedures: a review.
J Magn Reson Imaging 2000; 12: 37-45.
[2] Zhang NY,
Zhu XH,
Chen W.
Influence of gradient acoustic noise on fMRI response in the human visual cortex.
Magn Reson Med 2005; 54: 258-263.
[3] Hamaguchi T,
Miyati T,
et al.
Acoustic noise transfer function in clinical MRI: a multi-center analysis.
Acad Radiol,
2011; 18: 101-106.
[4] Hedeen R,
Edelstein W.
Characterization and prediction of gradient acoustic noise in MR imagers.
Magn Reson...