ECHOENCEPHALOGRAPH

Typical Number in Hospital: 2

Cost Bands: 3,4

References: 1

This is an ultrasonic A-scanner used to detect the position of the main membranes within the brain. An ultrasonic transducer applied to the head just above an ear will receive echoes (among others) from the membranes bounding the ventricles and midline (falx cerebri) and the position of these membranes may be displaced if the brain structures are distorted by a tumour, haematoma, or abnormal collection of cerebro-spinal fluid in the ventricles. Echoencephalographs have been used since the 1950s to examine patients with concussion or suspected cranial damage.

The apparatus consists of a transducer, a high-voltage pulse generator, an amplifier to augment the received echoes, and a processing circuit to present the echoes to the cathode ray tube in the form of a base-line indicating distance into the tissue, and vertical deflections corresponding to echo amplitude. Sometimes the apparatus has two transducers so that A-scans are presented simultaneously from each side of the head. The normal symmetry of the brain structures should be presented on each trace in the same positions. Any shift in the positions of the membranes will be immediately obvious.

An automatic midline shift detector has been produced called the 'midliner' which computes any shift without actual presentation of the A-scan.