Balanced Steady-State Free Precession Sequence (CISS/FIESTA/3D Driven Equilibrium Radiofrequency Reset Pulse) Increases the Diagnostic Yield for Spinal Drop Metastases in Children with Brain Tumors

Abstract

Identification of spinal drop metastases is important in the staging and management of pediatric patients with primary brain tumors. Our aim was to assess the diagnostic utility of the balanced steady-state free precession (bSSFP) sequence (CISS/FIESTA/3D driven equilibrium radiofrequency reset pulse) for the detection of spinal drop metastases in pediatric patients with primary intracranial tumors. This was a retrospective study of 44 pediatric patients with primary intracranial tumors undergoing MR imaging spine evaluation for drop metastases before radiation treatment. All patients underwent a whole-spine MRI with both bSSFP and postcontrast T1WI sequences. Two neuroradiologists independently reviewed only the bSSFP sequence, then 1 week later only the postcontrast T1WI sequence. Patients ranged from 1 to 18 years of age (mean, 7.1 ± 4.2 years) with 27 males and 17 females. The number of lesions per patient ranged from 1 to 13 and from 2 to 11 mm in size. Lesions suspicious for drop metastases were seen in 8 patients on the postcontrast T1WI (18%) compared with 10 patients on the bSSFP sequence (23%). Twenty-two drop metastases seen on the bSSFP sequence were not visible on the postcontrast T1WI, including nonenhancing drop metastases and multiple nodules of <3 mm. Interrater agreement was excellent for the bSSFP sequence (0.91) and the postcontrast T1 sequence (0.90). The bSSFP sequence increased the diagnostic yield for the detection of drop metastases in pediatric patients with primary intracranial tumors and was particularly advantageous for small drop metastases (<3 mm) and nonenhancing metastases, and it decreased the number of false-positives. The bSSFP sequence may be an important adjunct to postcontrast T1WI for the evaluation of drop metastases.