Evaluation of the Quality and Comparison of Dosimetric Parameters of Plans for Craniospinal Irradiation Using VMAT Method at Varian TrueBeam and Varian Halcyon Accelerators

Purpose: To carry out a comparative analysis of the dosimetric characteristics of plans for craniospinal irradiation (CSI) performed by the VMAT technique on Varian TrueBeam and Halcyon electron accelerators. Material and methods: Comparison of dose distributions was carried out for a group of 5 patients with tumors of the central nervous system. Contouring and planning were in Eclipse version 15.6. The following dose characteristics were calculated and evaluated: homogeneity index (HI), conformity index (CI), target coverage (CO) and constraints (lenses, esophagus, lungs, heart, liver, bowel bag and kidneys). Patient-Specific QA was performed to verify the consistency of the dose distribution calculated in the planning system and obtained at the accelerators. Results: For all CSI plans the target coverage metric was D98>95 % and constraints for critical organs were obtained. Homogeneity index was HI<=0.12 for two accelerators. The mean value of the CI conformity index was 1.09 for the TrueBeam accelerator, and CI=1.12 for the Halcyon. Gamma analysis showed results within tolerance both plans at TrueBeam and Halcyon. Conclusions have been made about the advantages and disadvantages of CSI on TrueBeam and Halcyon electron accelerators. Conclusion: It is possible to treat patients with the CSI method on the Halcyon accelerator using the VMAT method with the same quality as on the TrueBeam accelerator.