Robustness analysis to mitigate setup uncertainties in head-neck rapid arc treatment: A different approach to image-guided radiotherapy decision-making.

Aim: The occurrence of setup errors in external beam radiation is an inevitable aspect. As a result of technological progress in image verification, it became feasible to decrease its occurrence; however, complete eradication remained unattainable. Various methodologies have been implemented in clinical settings to measure and evaluate the extent of setup mistakes. Further analysis is required to gain a deeper understanding of the effects of setup mistakes on dose-volume histograms (DVHs), which will inform decision-making in the context of setup-related issues. This study aimed to quantify the extent of deviation observed in the DVH when a specific shift in a particular direction occurs within a pre-defined limit.

Material And Methods: Four head and neck patients were planned with Rapidarc modality using Eclipse™. The cone beam computed tomography image was acquired using Portal vision. Everyday, the treatment setup error was obtained from the offline review system. Plan data were imported into Computational Environment for Radiological Research software, and the perturbation of the DVH due to setup error was generated retrospectively. A total of 92 patient images and associated setup error information were analyzed in this study.

Results: Variations of dose to planning target volume (PTV) and organ at risk (OAR) using different parameters were analyzed to assess the uncertainty associated with day-to-day setup error, and intentional perturbation in DVH due to simulated error in all three Cartesian directions was analyzed. A low and moderate statistical correlation existed between the two patients' deviation in DVH due to the same amount of shift in the case of OAR. However, a positive correlation existed between the patients for PTV-related parameters.

Conclusion: Knowing the impact of shift data in DVH was helpful information that could be utilized further for different study data sets to see the contribution of shift data to dose uncertainty. For the PTV class, a solution for intentional shifts may be possible. For OAR dose simulation, individual patient-based simulation is required. This robustness analysis will help the user understand the setup error's implication in the DVH.

Advance In Knowledge: The present-day image-guided radiation therapy system was based on landmark matching based on different objectives. The standard linear accelerator-based setup or cobalt-based external beam radiotherapy (EBRT) setup had no information regarding the effect of the shift in DVH. This robustness analysis under the MATLAB platform was an effective tool for evaluating the setup error's impact on the DVH.