Optimization of myocardial nulling in pediatric cardiac MRI

Abstract

Background: Current protocols to determine optimal nulling time in late enhancement imaging using adult techniques may not apply to children. Objective: To determine the optimal nulling time in anesthetised children, with the hypothesis that this occurs earlier than in adults. Materials and methods: Sedated cardiac MRI was performed in 12 children (median age: 12 months, range: 1-60 months). After gadolinium administration, scout images at 2, 3, 4 and 10 min and phase sensitive inversion recovery (PSIR) images from 5 to 10 min were obtained. Signal-to-noise ratio (SNR) and inversion time (TI) were determined. Quality of nulling was assessed according to a grading score by three observers. Data was analysed using linear regression, Kruskal-Wallis and quadratic-weighted kappa statistics. Results: One child with a cardiomyopathy had late enhancement. Good agreement in nulling occurred for scout images at 2 (κ=0.69) and 3 (κ=0.66) min and moderate agreement at 4 min (κ=0.57). Agreement of PSIR images was moderate at 7 min (κ=0.44) and poor-fair at other times. There were significant correlations between TI and scout time (r=0.61, P<0.0001), and SNR and kappa (r=0.22, P=0.017). Conclusion: Scout images at 2-4 min can be used to determine the TI with little variability. Image quality for PSIR images was highest at 7 min and SNR optimal at 7- 9 min. TI increases with time and should be adjusted frequently during imaging. Thus, nulling times in children differ from nulling times in adults when using standard adult techniques. © Springer-Verlag 2011.