The acoustic hood: a patient-independent device improving acoustic noise protection during neonatal magnetic resonance imaging

Background: Magnetic resonance imaging (MRI) is today the imaging modality of choice to investigate the neonatal brain. However, the acoustic noise during scanning is very loud, often exceeding 100 dBA. Aim: To reduce the acoustic noise during MRI for neonatal patients. If effective, this would create a safer environment and also result in fewer aborted examinations due to poor image quality from patient motion. Methods: A passive acoustic noise protector, the acoustic hood, was built out of dampening material. Sound pressure measurements with and without the acoustic hood were performed using our clinical neonatal scan protocol, consisting of eight imaging sequences. The acoustic hood is placed over the newborn inside the MR scanner tunnel during the examination to absorb acoustic noise. Results: The acoustic noise level was substantially reduced using the acoustic hood. Peak sound pressure was reduced 16.18-22.21 dBA depending on the pulse sequence. For the entire frequency spectra, reduction were between 4-13.59 dBA again varying with the pulse sequence. Conclusion: Acoustic noise can be reduced further than before by using the patient-independent acoustic hood in addition to other noise protection. We recommend the use of three passive hearing protections during neonatal MRI: (1) dental putty, (2) paediatric ear muffs, and (3) the acoustic hood.