2.2 CT Technique
The pediatric patients in this study were examined in a quiet state, and for those who could not cooperate with the CT examinations, oral administration of 10% chloral hydrate (0.5 mL/kg) or intramuscular injection of phenobarbital sodium (5 mg/kg) was used. GE Lightspeed VCT 64 or Philips Brilliance ICT 256 was used to obtain the CT images. The scanning parameters were: tube voltage, 90-120 kV; tube current, automatic; slice thickness, 5.0 mm; slice interval, 5.0 mm; pitch, 0.984:1. The patients were injected with 2 mL/kg of nonionic contrast material (Omnipaque or Visipaque, GE Healthcare) at a rate of 2 mL/s via the peripheral vein of the forearm by a power injector. Corticomedullary phase (CMP) and nephrographic phase (NP) of post-contrast scanning were performed at 15-30s and 50-60s after contrast material injection, respectively.