Quantitative analysis of MR images in asphyxiated neonates: correlation with neurodevelopmental outcome

Abstract

Background and purpose: MR imaging has been shown to be of prognostic significance in the evaluation of asphyxiated neonates. The purpose of this project was to determine whether the use of intensity ratios in key regions of the brain might better detect regions of injured brain and thus improve the correlation of imaging findings with 12-month neurodevelopmental outcome.

Methods: Prospectively acquired MR studies of 53 asphyxiated neonates were reviewed retrospectively. Signal intensities from standard T1- and T2-weighted images of seven major brain regions that are affected in asphyxia were measured. Intensity ratios were calculated by dividing the signal intensity of each brain region by the signal intensity of the ocular vitreous. The intensity ratios were then correlated with 12-month neurodevelopmental outcome. These results were compared with correlations determined by a qualitative scoring system.

Results: The only significant statistical correlation between the intensity ratios and 12-month neurodevelopmental outcome were those of anterior watershed injury with the Mental Development Index of the Bayley Scales of Infant Development II. The qualitative measurements showed a strong correlation with many outcome parameters.

Conclusion: Standard qualitative assessment is more predictive of neurodevelopmental outcome than is quantitative analysis. This finding most likely reflects the inability of the quantitative assessment of intensity ratios to compensate for the day-to-day evolution of signal intensity of the injured neonatal brain. Anterior watershed injury may be predictive of abnormal cognitive outcome; examination of these patients at age 30 months will be important to determine the accuracy of this observation.

fig 1.

Locations of the 40-mm² voxels used in the study (see Table 1). The location of the eyeball voxel is obvious and not illustrated. The lines show how the measurements were made to keep the locations consistent. A, MR image shows location of voxels for basal ganglia (1) and thalamus (2). (The box adjacent to the trigone/occipital horn of the right lateral ventricle was for another project.) B, MR image shows location of voxels for frontal white matter (3). C, MR image shows location of voxels for prerolandic (4), postrolandic (5), posterior watershed (6), and anterior watershed (7) areas.