Ultrasound in Neurology

The ultrasonic focused beam method of producing selective, precisely localized, quantitatively reproducible lesions in the brains of experimental animals is illustrated. The acoustic calibration procedure, the surgical preparation of the animal, and the technique of irradiation are demonstrated in this motion picture. The complete instrumentation setup is shown in operation. A lesion is produced in the depths of the brain of a monkey. This technique, which is currently being used in studies of brain structure and function, was developed at the Bioacoustics Laboratory of the University of Illinois. A lesion of practically any desired size (as small as one millimeter in diameter) and shape can be produced at any specified location in the brain without disturbance of intervening tissue and without disruption of blood vessels even within the site of the lesion. In addition, it is possible by proper choice of the dosage to irreversibly affect fiber tracts (white matte) without destroying surrounding or neighboring nerve cell bodies (gray matte)r which receive the same dosage of radiation. This means that in producing lesions in white matter it is readily possible to retain the boundary between white matter and neighboring gray matter as the boundary of a lesion produced by ultrasound. Examples of ultrasonically produced lesions in both white and gray matter of a variety of sizes and shapes and at various depths in the brain will be illustrated by stained tissue sections. This procedure represents a significant advance over other methods of producing lesions which have been used up to the present time. The method has considerable potential value for neurosurgery.The support, in this research field, of the Physiology Branch of the Office of Naval Research is acknowledged.