LINAC-ACCELERATOR-RADIOSURGERY

A survey is given of the actual possibilities and limitations of the u se of linear accelerators (Linac radiosurgery systems) for intra = cra nial radiosurgery. Depending on the collimator size, spherical fields from 5-54 mm in diameter can be irradiated with dose gradients from 10 % (large fields) to 20% (small fields) per millimeter distance between surface and treatment volume. This is comparable to the possibilities of Gamma-Knife and Proton-irradiation. Optimal mechanical adjustment of gantry and linac table are necessary for the required stability of the isocenter. Mechanical inaccuracy should be smaller than 0.8 mm. Ad vanced computerized 3D-treatment planning systems are indispensable pr erequisites for accurate treatment and use of the flexibility of the l inac system. Future developements are outlined.