Dosimetric Comparison of two linear accelerator based radiosurgery system for Intracranial tumours with Rapid Arc and Dynamic conformal Arc therapy

Introduction : Present study focused on dosimetric evaluation of Edge and Novalis Tx (NTx) linear accelerator (LA) based radiosurgery system by using rapid arc (RA) and dynamic conformal arc (DCA) planning techniques.Materials and Methods: Forty patients with brain lesions of variable sizes (1.1-15.98 cc) were planned for Edge and NTx system by using RA and DCA planning techniques on eclipse treatment planning system version 13.6 (Varian Medical Systems, Palo Alto, CA, USA). All the plans were evaluated on the basis of paddick conformity index (PCI), homogeneity index (HI) and gradient index (GI). The maximum doses to organs at risk (OAR), V12Gy, V10Gy and V5Gy for healthy brain tissue were also evaluated for all the plans. The treatment delivery efficiency for both the systems was also evaluated. Results: The mean PCI and GI for both RA and DCA plans were found to be better in Edge as compared to NTx system (PCIEdge,RA=0.77±0.1, PCINTx,RA=0.66±0.11, PCIEdge,DCA= 0.69±0.12, PCINTx,DCA= 0.67±0.12). Significant difference in HI, doses to OAR and V12Gy, V10Gy and V5Gy brain volume was observed for both the systems with p-value less than 0.05. Reduced treatment time was observed in Edge LA as compared to NTx LA. Conclusion: Edge LA produced clinically better target volume conformity, rapid dose fall-off, reduced reduction in normal brain volume irradiation and treatment time compared to NTx. Thus in the set of patients plan evaluated it was noted that Edge stereotactic suite in more efficacious and diametrically suitable for intracranial radiosurgery.