Purpose: To implement and evaluate the effect of a couch model in the RayStation TPS.
Methods: Using a combination of CT scans and vendor-provided structure sets, structure templates were created in the RayStation TPS using the vendor-provided tool. The couch template was inserted into a plan with density overrides to simulate the presence of the intended treatment couch. To verify the validity of couch models, 3-D dose comparison was performed using an ion chamber and SunNuclear ArcCHECK. QA files were generated with and without the couch model and compared to measured results to determine the effectiveness of the model.
Results: Models have been created for a kVue Calypso 6D couch and Varian IGRT couch. Six plans were evaluated for the kVue couch; ion chamber measurements at isocenter improved for every beam run, and by an average of 2.42%; ArcCHECK gamma results improved for each beam both in the 3mm/3% and 2mm/2% evaluations, by an average of 1.67% and 3.71% respectively. Nine plans were evaluated for the Varian IGRT couch; ArcCHECK gamma results improved for almost all beams in the 3mm/3% criteria (average of 1.66%) and in the 2mm/2% criteria (average of 3.93%). Of the seventy-two beams run on the Varian IGRT couch only three showed worse results, and all by less than 1%.
Conclusion: A convenient method for the deployment of couch models in the RayStation TPS has been investigated and implemented. Test plans were created and delivered to a 3-D QA device and ion chamber to prove that results improved in the vast majority of cases – validating the need for and accuracy of the inclusion of a couch model in treatment planning.