THE PHYSICAL PRINCIPLES OF GAMMAKNIFE THERAPY

Stereotactic radiosurgery is a treatment modality that depends upon the accurate and precise geometric delivery of radiation to destroy a target in a closed skull which is well defined by means of high technological imaging procedures and stereotactic localization within a Leksell frame. The Leksell Gammaknife (LGK) delivers a single high dose radiation produced from 201 Co60 sources. Each narrow beam is focused on the target where all beams intersect to cause lethal damage while sparing adjacent normal tissue. Because of the uniqueness of the unit, the hemispherical localization of sources, target localization and treatment planning algorithm which are differing from other high precision techniques of radiotherapy, we described these specifications on the paper. The physical description of the unit, the procedure of patient treatment, the dose calculation and treatment planning algorithm are presented with schematic diaghrams and photographs those taken on LGK 98 model B in the clinic.