Room: AAPM ePoster Library
Purpose: The purpose of this research was to evaluate volumetric modulated arc therapy (VMAT) treatment plan quality during the transition from one treatment planning system (TPS) to another.
Methods: Our department has transitioned from Pinacle TPS to the RayStation one. To evaluate the quality of the plans during this period, we identified the last ten (n=10) head and neck patients that were planned with Pinnacle and the first eighteen (n=18) planned with RaySearch. All patients were treated using VMAT with two arcs on an ELEKTA VersaHD linear accelerator. Another set fifteen (n=15) of previously treated patients using step and shoot Intensity Modulated Radiotherapy (IMRT) and planned with IMRT was used to compare treatment modalities. The same physician had segmented all patients, and the same dosimetrist has optimized all plans. Collected data from DVHs were mainly used for the comparisons. Such data included DVHs of the parotids, mandible, spinal cord, and the left and right cochlea as well as conformity and homogeneity of the planning target volumes (PTV).
Results: Our comparisons showed that the spinal cord maximum as well as the area under the DVH was statistically significant lower for the RaySearch plans (p<0.05). Also, the high dose PTV (PTV 6996) homogeneity was higher for RaySearch plans (p<0.05). Other organs at risk did not have a statistically significant difference. Also, no differences in Pinnacle plan quality were observed between VMAT and IMRT plans.
Conclusion: The treatment plans optimized with the RaySearch TPS were shown to spare the spinal cord and improve PTV homogeneity compared to those by Pinnacle. The advanced features of the RaySearch TPS such as multi-criterial optimization, prescription to a volume, etc. are most likely the reason for the differences observed in this study.