Dosimetric comparison of the plans obtained with iris, fixed colimator and multi-leaved colimators in treatment planning of brain metastases in the cyberknife radiosurgical system

In this study, dosimetric comparison and evaluation of virtual treatment plans for three different collimators (FIXED Collimator, IRIS and MLC) were performed using the planning system of 10 brain metastasized cases diagnosed with breast cancer in the CyberKnife radiosurgery system. The aim of this study is to evaluate dosimetrically the virtual treatment plans made by different methods in the treatment planning system of brain metastasis patients diagnosed with breast cancer. For this purpose, archival information about 10 cases with brain metastases diagnosed with breast cancer that were treated at the Department of Radiation Oncology of the Faculty of Medicine of Bursa Uludag University was obtained retrospectively and virtual treatment plans were made in the planning system. In the plans made, the prescribed dose was 18 Gy in 3 fractions and the isodose curve was defined at 80%. The target volume doses, critical organ doses, homogeneity, conformality, gradient index, monitor unit (MU), NOD and treatment duration data of the treatment plans obtained after the completion of the study were compared. For the obtained plans, attention was paid to the fact that isodose envelops 95% of the target volume and protects critical organs. Dose volume histogram (DVH) was used to obtain dose distributions in the created plans. In this study, the data obtained in the statistical package for the social sciences (SPSS) program were analyzed using Repeated Mesure Anova and Friedman tests in a three-way comparison using statistical package for the social sciences (SPSS). PTV (Dmax, Dmin, D2), Brain-PTV (V8, V10, V12), left eye, left-right hippocampus, brain stem, optic chiasma, pituitary gland, left lacrimal, left and right cohlea, HI and GI values were obtained close to each other and no significant difference was found. The IRIS collimator for the left-right lens, right eye, left optic nerve and CI, the FIXED collimator for the right optic nerve, right lacrimal and NCI, and the MU, NOD and MLC for the duration of treatment were found to be good and a significant difference was found.