Effect of the Skull in Degrading the Display of Echoencephalographic <i>B</i> and <i>C</i> Scans

Abstract

The skull causes topographical mislocalization in range of images of the brain due to the increased velocity of sound through its varying thickness. It also causes mislocalization in azimuth by refraction. Similarly, mislocalization in azimuth may result from echoes off the central axis of the transducer but distant to sonolucent areas of the skull, being displayed as if they lay in the central axis. Resolving power is degraded in range by the display of ringing due to either increased amplitude from strong echoes or reinforcing reverberation with the skull. Resolving power is degraded in azimuth because the varying attenuation at different parts of the skull will cause uniform point reflectors sometimes to return strong echoes, which will be displayed as a large image.