Kim Annink

242 Chapter 11 Figure 3: Local SAR levels in adult head (left) and Charlie in the different coil positions. Shifts of an infant in x and y directions are unlikely because of limited space and therefore the re- sults are not included in the Figure. The SAR values when infant Charlie was positioned 50mm in x or y direction were comparable with the +50mm FH position. The SAR per B 1 2 was lower in the infant model than in the adult models, meaning that less power is needed to reach the same B 1 ; except for the +50mm FH position. Preparation – Acoustic Noise protection The background noise in the sound booth was 28dB(A). The 7.0T hood attenuated the acoustic noise by 8.5dB and the 3.0T hood 7dB (Table 2). Table 2: Acoustic noise levels in dB(A) with use of no hood, the 3.0T hood and the newly developed 7.0T hood. Both ends of the bore Sides of the bore Sides and ends of the bore No hood for acoustic noise protection 60.0dB(A) 58.5dB(A) 62.5dB(A) 3.0T Nordell hood for acoustic noise protection 54.0dB(A) 51.0dB(A) 55.5dB(A) Prototype 7.0t hood for acoustic noise protection 54.0dB(A) 43.0dB(A) 54.0dB(A) Without hearing protection the artificial ear measured 80dB(A). The Alpine Muffy Baby reduced the acoustic noise to a level of 56dB(A) and the use of only the Natus Minimuffs resulted in 73.4dB(A). The combination of both, not totally closing of the