Origin of Echoes in the Echoencephalogram

Detection of ventricular landmarks by two dimensional ultrasonography.

“…They appear as two short but distinct sonic lines placed on each side and parallel to the anterior portion of the septum and represent the most narrow and inferior portion of the ventricles at the level of the anterior horns. This was demonstrated experimentally by Lithander (1961) in excised brains, and confirmed by Grossman (1966) four years later. They were studied by Ford and McRae (1966) with unidimensional sonograms and also by direct comparison with pneumoencephalograms.…”

“…This was confirmed by Jeppsson (1960) in infants, and by ter Braak, Crezee, Grandia, and de Vlieger (1961), using simultaneous US and pneumoencephalography (PEG). An experimental confirmation of these data was given by Lithander (1961) who introduced a needle indicator in proximity to the reflecting interfaces on excised brains. Ford and Ambrose (1963) described the behaviour of the A-mode echoes arising from the walls of the third ventricle in relation to air study and curved interfaces.…”

“…The possibility of detecting other landmarks of the ventricular system was suggested also by Tanaka, Kikuchi, and Uchida (1961) and experimentally by Lithander (1961), who could identify the A-echoes arising from the lateral wall of the occipital horns and of the portion of the anterior horns just anterior to the foramen of Monroe. Ambrose (1963) suggested a technique for localizing the walls of the lateral ventricles by A-scan.…”

References

“…encephalographic methods in outlining the normal and pathological shape of cerebral ventricles in children. Ultrasonics 10: 140,1972. 5.…”

Studies in Ultrasonic Echoencephalography—V. Echoes Obtainable from a Plastic Skull

“…Nor does it help to introduce foreign objects into cadaver brains at various positions until their echoes coincide with the position on the time base of the echo under investigation as Lithander (1961) and others have done. For the reasons mentioned above, this procedure merely shows that the two echoes lie approximately equidistant from the transducer at any point on a segment of a sphere centred at the transducer face and the size of the segment will vary directly with the intensity of the reflection factor of the unknown object, the power of the ultrasonic beam and the sensitivity of the amplifier, so that a strong reflector could lie at a considerable distance away from the central axis of the sonic beam and yet still give rise to an echo of equal amplitude as a weak reflector situated near the central axis of the sonic beam.…”