Analysis of the intensity of radio-frequency signals in intracranial ultrasonography of preterm infants.

Abstract

The purpose of this study was to evaluate the usefulness of analysis of the intensity of radio-frequency (RF) signals in intracranial ultrasonography of preterm infants. Twenty neonatal infants admitted to the neonatal intensive care unit of our hospital were included in this study. Their gestational age was 33-35 weeks. The studies were performed with a System 5 ultrasound system with 3.0-and 5.0-MHz transducers. The transducer was placed on the anterior fontanel to obtain images. Regions of interest were determined based on B-mode images and were positioned at the thalamus, caudate nucleus, cerebral white matter, cerebellum, brain stem, and lateral ventricle. The software used for analysis of the RF signals was EchoMAT (Vingmed Ultrasound). The RF signals of the ventricle and the choroid plexus showed the lowest and the highest intensities, respectively. The intensities of the brain stem and vermis signals were the same, and were higher than the intensity of the cerebellar hemisphere. The thalamus and caudate nucleus showed macroscopically identical brightness levels; however, the intensity of the thalamus was lower than that of the caudate nucleus. The intensity of subependymal hemorrhage was lower than that of the caudothalamic groove. The intensity of subependymal cyst was the same as that of the lateral ventricle. The RF signal frequencies and intensities were distinctive in each tissue. The results of this study suggest that measurement of RF signal intensity may be useful to differentiate macroscopically similar lesions.