Easy and effective acoustic noise protection in neonatal MRI

Abstract

Background: The effect of acoustic noise during MRI is unclear and difficult to study in neonatal individuals. High acoustic noise levels during MRI can lead to anxiety, motion artifacts, and incomplete examinations due to newborns waking up. The acoustic noise is clearly a risk factor in MRI and hearing protection must be used. Usually, three passive attenuators are used: (1) a moldable dental putty (2) Natus minimuffs and (3) regular earmuffs, which is difficult to fit properly on the small neonate. Objective: To develop a new simple, safe and reliable method for reducing the acoustic noise in neonatal imaging. Design/Methods: An acoustic hood of dampening material was built (figure 1) and placed inside the MR-scanner tunnel. Acoustic noise levels were tested with and without an acoustic hood during 12 common pulse sequences to achieve a substantial dampening effect. The acoustic hoods were made of acoustic foam rubber, 38–104mm, combined with a 4mm isolating mat and a closed exit in the back of the MR-scanner. Results: Acoustic noise levels were reduced by 6–24dB on the A-weighted scale (figure 2). A substantial dampening effect was achived when using a acoustic hood (figure 3) that left at least 50mm of space outside the Philips SENSE Head coil. Acoustic noise levels during our neonatal MRI studies ranged from 80–112dB (A-weighted); earlier publications report similar acoustic noise levels of 81–117dB [3, 4, 5]. The acoustic hood was used in neonatal MRI without affecting the image quality and it was easily inserted from the back of the MR-scanner without interfering with the examination (figure 1). Conclusions: The acoustic hood is a reliable way of attenuating acoustic noise thereby facilitating the neonatal MRI examination. It may also reduce the need for supplemental sedative medications.