Quantitative Tissue Echogenicity of the Neonatal Brain Assessed by Ultrasound Imaging

Abstract 

The aim of this study was to propose a method for measuring the echogenicity of several neonatal brain structures for quantitative interpretation of ultrasound images. To do this, 40 preterm neonates (24-34 weeks' gestation) with adequate birth weight for gestational age were studied. On the third day after delivery, anterior fontanelle ultrasound imaging of the brain was performed in standard coronal and sagittal views. Four regions-of-interest (ROIs) were identified: periventricular, choroid plexus, cerebellar vermis and basal ganglia. Two consecutive images from each ROI were digitally stored. For off-line analysis, the ROI corresponding to each structure was delineated and the mean pixel brightness (PB) calculated. In addition, the brightness of bone tissue obtained at the same depth of the studied ROI was calculated. This value was considered as the maximum possible echogenicity for that individual image. The relative echogenicity (RE) was then calculated as: PB ROI/PB BONE^∗100. Differences in RE between the ROIs and RE variations according to gestational age and reliability reproducibility were determined. We found that among the studied structures, RE values (mean/SD) were significantly higher in the choroid plexus (mean [SD] 56.38 [6.0] and in the cerebellar vermis 51.20 [6.0] than in the basal ganglia 37.29 [5.7] and the periventricular area 37.04 [5.6]) (p<0.05). These values showed no variation in relation to gestational age at birth. Interobserver reproducibility was 0.91 in the choroid plexus, 0.89 in the cerebellar vermis, 0.82 in basal ganglia and 0.77 in the anterior periventricular area. In conclusion, semiquantitative estimation of RE offers a reproducible method for evaluating at-risk areas of the neonatal brain. (E-mail: fpadilla@clinic.ub.es)

Key Words: Ultrasound, Neonatal brain, Tissue relative echogenicity, Digital analysis, Quantification, Pixel brightness