Incidence of Setup Errors in Patients Treated with Radiotherapy in the Faculty of Medicine, Vajira Hospital
Kamonrat Sueangamiam, MSc1, Kanisa Rongsriyam, MD2
Affiliation : 1 Department of Radiological Technology, Faculty of Medicine, Vajira Hospital, Navamindradhiraj University, Bangkok, Thailand,2Department of Radiology, Faculty of Medicine, Vajira Hospital, Navamindradhiraj University, Bangkok, Thailand
Objective: To study incidents of radiation therapy setup errors and factors affecting patients treated with radiation therapy to assess treatment effectiveness and provide fundamental data for the continued care of future patients at the Faculty of Medicine, Vajira Hospital.
Materials and Methods: The retrospective study was conducted from December 2023 to March 2024 on 39 patients who underwent radiation therapy in the TrueBeam linear accelerator, receiving MV-kV and CBCT images before each treatment session. These images were compared with CT images obtained from the treatment simulation process to determine the positional setup errors in all three directions. Subsequently, the values obtained were used to calculate systematic and random errors. The statistical analysis was performed using percentages and univariate analysis to assess statistical correlations.
Results: A total of 434 MV-kV and CBCT images were collected. It was found that the cumulative incidence of radiation therapy setup errors was 0.65, with systematic and random errors in the vertical (Vrt.), longitudinal (Lng.), and lateral (Lat.) directions of patients being 0.23, 0.22, 017, and 0.20, 0.21, and 0.21 cm, respectively. Moreover, the use of different patient immobilization devices significantly impacted the setup errors, particularly in the Vrt. direction. Conversely, other factors, such as gender, radiation technique, treatment site, and bladder preparation did not show significant correlation with setup errors values.
Conclusion: Setup errors were detected in every treatment session, and the measurement and correction of these errors before treatment using MV-kV and CBCT images significantly improve the accuracy and precision of radiotherapy. The choice of immobilization devices plays a crucial role in minimizing setup errors. This approach can reduce the PTV margin and increase the radiation dose to the cancerous tumor. Therefore, it is essential to determine the setup errors and appropriate radiation margins specific to each institution.
Received 24 April 2024 | Revised 7 August 2024 | Accepted 16 July 2024
Keywords : Radiotherapy; Setup error; Systematic error; Random error
