Irradiation of small structures through the intact skull.

The physical conditions for producing minute disc-shaped lesions for functional radiation surgery by means of narrow beam irradiation are discussed. The intention was a treatment procedure for routine clinical use and with high physical and mechanical reproducibility. The possibilities of using high energy electrons, supervoltage roentgen radiation, gamma emitting nuclides or fast neutrons in a technique for routine clinical use were investigated. The radiation of choice taking physical properties, radiation biologic factors and practical circumstances into account was considered to be 60-Co gamma radiation. A treatment apparatus containing 179 60-Co sources within a spherical sector of 70 degrees latitude and 160 degrees longitude was constructed.