A Preliminary Evaluation of an Online Adaptive Radiotherapy Emulator for Helical Tomotherapy
Abstract
Purpose
To provide an early assessment of the use and usefulness of a new helical tomotherapy online adaptation emulator tool.
Methods
This study investigated using the Adapt LTE online adaptive radiotherapy emulator tool powered by Accuray Cenos, for retrospectively evaluating previously delivered Precision Radixact tomotherapy treatment plans against original therapy objectives. Clinical planning CTs, structures and treatment plans with their corresponding daily pre-treatment images and setup/registration parameters were imported into the Adapt LTE system to emulate online adaptive treatment processes. For each emulated treatment fraction, Adapt LTE automatically deformed contoured structures and calculated a corresponding dose distribution on the daily image for that fraction. Users had the option of accepting or editing contoured structures, accepting the initial treatment plan or re-optimizing the treatment plan based on the new structure geometry.
Results
Preliminary evaluations were completed using 157 of fractions from 9 female pelvis treatments. Dosimetric quality of adapted treatment plans often exceed the quality of simply recalculating the planned treatment on the daily image, and some adapted fractions also achieved improved plan quality metrics compared to the initial treatment plan calculated on the planning CT. This latter result occurred when the patient anatomy shifted into arrangements where treatment goals were more easily met than on the day of the planning CT. Further work is underway, to evaluate how these results from using Adapt LTE for Radixact tomotherapy plans (ie. the features of adapted treatment plans selected for hypothetical delivery) may be affected by decisions made by different users during the adaptation workflow.
Conclusion
Access to the Adapt LTE emulator system is allowing multiple users to rerun and compare results for specific treatment fractions, enabling systematic investigations of the performance of the Radixact online adaptative radiotherapy system to be completed retrospectively without affecting or delaying the treatments of current patients.