PURPOSE: The purpose of this study was to compare conventional 1.5T MRI with a dedicated 1T neonatal MRI at term equivalent age using a validated scoring system for assessing the severity of brain abnormality at term-equivalent postmenstrual age.
METHOD AND MATERIALS: This was a prospective, non-randomized, feasibility study. Premature infants born prior to gestational age of 28 weeks, or born between 28-32 weeks of gestation with IVH, US abnormalities, neonatal morbidity or abnormal neurological exam underwent scanning with both conventional 1.5T and dedicated neonatal 1T MRI, after parental consent was obtained. Neonates scanned only on the 1T MR system, with congenital cerebral malformations; cardiorespiratory instability, requiring mechanical ventilation, weighing <1kg, or >4.5 kg; with a head circumference (HC) >38 cm; or neonates with mechanical or electrical devices (e.g. metallic implants) were excluded. MRI scans included identical orthogonal T1 and T2 imaging, performed on a conventional 1.5T MRI (Aera, Siemens), as well as on a 1T MRI (Embrace, Aspect) located in the NICU. No more than 48 hours elapsed between the two studies. 2 radiologists separately applied the Kidokoro scoring system to images from both conventional and NICU systems, in a blinded fashion. Severity of scores was classified as normal, mild, moderate and severe (0-3, 4-7, 8-11, 12≤, respectively). Scoring of both scans was compared using a paired t-test and Kappa coefficient as measurement of concordance.
RESULTS: 30 neonates were scanned using both systems. Reader 1 respectively graded 11, 10, 4 and 5 infants with normal, mild, moderate and severe brain abnormality on the 1T neonatal MRI; 11, 8, 5 and 6, respectively, on the 1.5T MRI, with no statistical difference between the scores (P=0.96). The observed Kappa coefficient was 0.86 (std error 0.07, CI 0.72-1). Reader 2 respectively graded 10, 10, 5 and 5 neonates with normal, mild, moderate and severe abnormality on the 1T neonatal MRI and 11, 9, 3 and 7 on the 1.5T MRI. No statistical difference was seen between the scores (P=0.99). Observed Kappa was 0.86 (std error 0.07, CI 0.72-1). Inter-rater concordance was excellent, with observed Kappa of 0.91 for both machines (std error 0.06, CI 0.78-1)
CONCLUSION: There is near perfect concordance between the 1T NICU dedicated and clinical 1.5T MRI systems when using the Kidokoro global brain abnormality score for term equivalent age infants.
