Investigation of acoustic noise on 15 MRI scanners from 0.2 T to 3 T

Acoustic noise levels for fast NM pulse sequences were surveyed on 14 syste ms with field strengths ranging from 0.2 T to 3 T. A microphone insensitive to the magnetic environment was placed close to the magnet isocenter and c onnected via an extension cable to a sound level meter outside the scan roo m. Measured noise levels varied from 82.5 +/- 0.1 dB(A) for a 0.23 T system to 118.4 +/- 1.3 dB(A) for a 3 T system. Further measurements on four of t he closed-bore systems surveyed showed that: 1) pulse sequence parameters ( particularly FOV and TR) were more influential in determining noise level t han field strength, 2) the noise level was found to vary along the z-direct ion with a maximum near the bore entrance, and 3) in one of two systems tes ted there was a significant increase in noise with a volunteer present inst ead of a test object. The results underline the importance of hearing prote ction for patients and for staff spending extended periods in the scan room . (C) 2001 Wiley-Liss, Inc.