Kim Annink

240 Chapter 11 We measured the attenuation of the Alpine Muffy Baby and Natus MiniMuffs using the Brüel & Kjaer Type 2250 G4 SLM and Brüel & Kjaer Artificial Ear Type 4153. A stimulus (Decos AudioNigma, Noordwijk, the Netherlands) of 80dB(A) was sent to an artificial ear. Figure 2: Set up for measuring acoustic noise at the MR table in the presence of the hood. This test setup consisted of a dummy bore with similar dimensions as the 7.0T MR system with a 10mm plastic plate (POM) to create an MR table. The speakers producing the sound positioned at 28cm distance around the dummy bore to mimic the sound produced by the MR scanner. Study population Clinically stable infants, between term (equivalent) age and the (corrected) age of three months were included in this pilot study. Infants with respiratory support or an intravenous catheter were excluded. They underwent a 7.0T MRI immediately after their routine 3.0T MRI scan (both Philips Medical Systems, Best, The Netherlands). All infants were sedated with chloral hydrate prior to the 3.0T MRI in combination with the feed-bundle technique, as parts of routine clinical care. An additional dose of chloral hydrate prior to the 7.0T MRI was not allowed by the medical ethical committee. For neonatal scans of the brain at 7.0T, the 2-channel transmit-32-channel receive head coil (Nova Medical, Inc, Burlington, MA, USA) was used. The selection of sequences was based on clinical indication. Details of the scan protocols can be found in Supplemental Table 1. Hearing was protected as described above. Safety parameters were monitored before, during, between and after the MR scans. We monitored heart rate, peripheral