Development of a Computerized Measurement Method on Three Dimensional Alignment of the Target Center in a Stereotactic Radiosurgery System

Abstract

In stereotactic radiosurgery, which treats a small region in the brain with a concentrated high-energy beam, it is critical to align the target center with the iso-center of the radiation system in order to minimize the volume of the surrounding normal tissue being irradiated. The accuracy of the alignment has been evaluated in a two-dimensional space by using a stainless ball phantom image. We have developed a computerized measurement method to measure three-dimensional alignment errors between the iso-center of the linear accelerator and the target center. Phantom images on X-ray films irradiated at eight different positions were employed in this new method. This program decreases the average alignment error from 0.31 to 0.12 mm, so it can improve the accuracy of treatment in a clinical setting.