Ultrasonography in Children

Abstract

Ultrasound is the manifestation of a high frequency mechanical vibration. The sound waves produced are beyond the range of human hearing, i.e., 1 to 10 mHz. The sound waves travel through liquids and solids but cannot pass through air or vacuum. Ultrasonic energy is produced by a transducer, the power to which is supplied by a high-voltage pulsing circuit in an amplifier (ultrasonoscope). Ultrasonography has been used successfully in the examination of pediatric patients. One of the most common uses has been to measure shifts of the midline structures of the brain. By utilizing the standard echoencephalographic approach established for adults, and positioning the transducer above the ears in the temporoparietal regions, echoes are recorded from the midline structures. Ultrasonography is used as a preliminary study prior to more definitive procedures such as pneumoencephalography or arteriography, particularly in the presence of localizing signs. It has also been used to detect hydrocephalus and to follow changes in ventricular size which occur after ventricular shunting procedures. In fact, this is the easiest way to serially monitor the response to decompression. In many hospitals, ultrasonagraphy is considered to be the primary diagnostic study for the detection of pericardial effusion. Ultrasonic examination of the heart of pediatric patients with suspected congenital or acquired heart disease appears to be a promising new diagnostic technique. It has been successfully used to evaluate a number of abnormalities: great vessel transposition, cardiac chamber size and position, valve motion, and ventricular wall thickness. Extensive research is in progress to establish both normal values and patterns for differentiating various congenital abnormalities.