title: 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.
  
  
  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).
  
  
  CONCLUSIONS
  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.
authors: Department of Pediatrics, Division of Pediatric Cardiology, Stollery Children's Hospital, University of Alberta, Walter C Mackenzie Health Science Centre, 8440 112th St, Edmonton, Alberta, Canada. etham@ualberta.ca
authors: Edythe B
authors: EB
authors: Tham
authors: Ryan W
authors: RW
authors: Hung
authors: Kimberley A
authors: KA
authors: Myers
authors: Cinzia
authors: C
authors: Crawley
authors: Michelle L
authors: ML
authors: Noga
mesh_terms: D002675:Child, Preschool; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D005682:Gadolinium / Q000008:administration & dosage*; D006330:Heart Defects, Congenital / Q000473:pathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007223:Infant; D018810:Magnetic Resonance Angiography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D005682:Gadolinium