Reactions of young children to the MRI scanner environment.

Seventy children aged 2 to 7 years were exposed to the MRI environment through a series of steps typical of a research study. Their willingness to proceed through the process was used to estimate the prevalence of fear. Thirty-seven children (53%; 95% confidence interval [41%, 65%]) completed the approach sequence. Although the correlation of child age in months (Mean (M) = 60.1, standard deviation = 16.5, N = 70) and highest successful step (M = 5.8, standard deviation = 2.6, 95% confidence interval [5.2, 6.4]) completed was not statistically significant at the 0.05 level, r (68) = 0.21, P = 0.08, 95% confidence interval [-0.03, 0.42], the proportion of children aged 6-7 years who successfully completed all steps (14 of 21, 67%, 95% confidence interval [50%, 84%]) was significantly different from the proportion of children aged 2-3 years who completed all steps (six of 23, 26%, 95% confidence interval [11%, 41%]) (Fisher's exact test, two-tailed P = 0.0148). A failure rate of at least 50% should be included into group size calculations when performing studies with young children (2-7 years), in addition to motion and other experimental factors.