method for detecting abnormalities within the cranial cavity, based on the reflection of high-frequency sound pulses delivered to the head through a probe held firmly to the scalp. The reflected pulses from the skin, brain ventricle, skull, and other head structures are recorded and amplified with a cathode-ray oscilloscope, giving a measure of the distance between the probe and the reflecting surfaces. The method is rapid, painless, and harmless; it is a good screening test for mass lesions causing brain shift and is well adapted for emergency examination of patients with brain hemorrhage. See also brain scanning.