| 摘要 |
PURPOSE: To accurately obtain an isodose contour without modifying the accelerating head of a linear accelerator by passing radiation beams through a variable-length path having a material (fluid) substantially equivalent to the tissue of a patient, before the radiation beams enter the patient. CONSTITUTION: A patient 305 is placed on the rotary bed of a linear accelerator with either a target on the cranium 308 or an obstacle 306 placed at the center of a collimator 304' used for focusing the radiation beams 311 of the linear accelerator. As the collimator 304' moves along a path 308, it increases or decreases its length from a means 315 so that the end of a variable-length path 317 makes contact with the cranium 308 of the patient 305, and then it focuses the radiation beams 311 toward the obstacle 306 via the variable-length path 317 having a material 318 which is equivalent to living tissue. Thus when the collimator rotates around the cranium of the patient, the amount of radiation focused toward the obstacle is held at a fixed value, so that time current linear accelerator can be used without modifying its accelerating head. |
