A New Approach with Combined Stereotactic Trans-multiarc Beams for Radiosurgery Based on the Linear Accelerator: Photon Knife

Choi, Tae Jin; Kim, Jin Hee; Kim, Ok Bae

Abstract

PURPOSE: To get an acute steepness of dose gradients at outside the target volume in intracranial lesion and a less limitation of beam selection avoiding the high dose at normal brain tissue, this Photon Knife Radiosurgery System was developed in order to provide the three-dimensional dose distribution through the reconstruction of CT scan and the combined stereotactic tranmultiarc beam mode based on linear accelerator photon beam.
METHODS
AND MATERIALS: This stereotactic radiosurgery, Photon Knife based on linear accelerator photon beam was provided the non-coplanar multiarc and trans-multiarc irradiations. The stereotactic trans-multiarc beam mode can be obtained from the patient position in decubitus. This study has provided the 3-dimensional isodose curve and anatomical structures with the surface rendering technique.
RESULTS
In this study, it shows that the dose distributions of stereotactic beam mode are significantly depended on the selected couch and gantry angle in same collimator size. Practical dose distribution of combined stereotactic trans-multiarc beam has shown a more small rim thickness than that of the non-coplanar multiarc beam mode in axial, sagittal and coronal plane in our study. 3-Dimensional dose line displayed with surface rendering of irregular target shape is helpful to determine the target dose and to predict the prognosis in follow-up radiosurgery.
CONCLUSION
3-Dimensional dose line displayed with surface rendering of irregular target shape is essential in stereotactic radiosurgery.This combined stereotactic trans-multiarc beam has shown a less limitation of the selection couch and gantry beam angles for the target surrounding critical organs.It has shown that the dose distribution of combined trans-multiarc beam greatly depended on the couch and gantry angles.In our experiments. the absorbed dose has been decreased to 27 % /mm in maximum at the interval of 50% to 80% of isodose line.