ИСТИНА

Objective. A comparison of dosimetric patametres of CyberKnife (CK) and Novalis plans for hypofractionated treatment of different intracranial pathologies. Materials and Methods. 15 patients with single intracranial tumors (tumors have different histology, volume, and localization) previously treated on the CyberKnife were selected for comparison of dose distribution. Targets and critical structures were contoured by MultiPlan and transferred in iPlan with CT scan of the patient for recalculation. Mean doses in targets for each patient were equal in both planning systems. Homogeneity index (HI), coverage (CO), conformity indexes (CIRTOG, nCI), gradient indexes (GI50, GI25), the dose in normal tissues (V10, V12) and critical structures (optic nerves, chiasm, brain stem) were obtained from DVH. To automate processing of DVH a software was developed in Borland C++ Builder 6.0. Results. The most informative indicators for comparing plans were the GI50 gradient index, the conformity indexes CIRTOG and nCI, as well as indicators of radiation doses on the brain V10 and critical structures. While Novalis provided more homogeneous dose distributions within the target, CK irradiated less exposed volume in normal tissues. Doses in critical structures, located far from the target, are lower for Novalis. If the tumor is adjacent to critical organs, CK allows to reduce the dose in them more effectively, due to the high dose gradient outside the target.