| dc.description.abstract | Patient setup is crucial in radiotherapy since treatment is delivered as fractionated treatment over a period of
time. Using own institutional margins by considering the setup errors will provide better radiotherapy outcome.
Therefore, this study aims to assess set up errors for head and neck cancer patients using an electronic portal
imaging device at Apeksha Hospital, Maharagama, Sri Lanka. A total of 101 head and neck cancer patients who
were immobilized with thermoplastic mask were selected in this study. Stored data from July 2021 to July 2022
were obtained from ARIA patient management system in the Varian 2300CD Unit at Apeksha Hospital. In order
to calculate systematic and random errors, translational errors in all directions were collected utilizing 303 pairs
of orthogonal portal images. Moreover, three different algorithms were used to obtain the margin of clinical
target volume (CTV) to planning target volume (PTV). The estimated systematic and random errors in the
directions of antero-posterior, superior-inferior and medio-lateral are 0.13 cm, 0.10 cm and 0.08 cm, and 0.22
cm, 0.21 cm, and 0.19 cm respectively. Less than 0.5 cm margin were obtained by applying three different
algorithms. This study indicates that using a 0.5 cm margin for head and neck cancer patients treating in 2300CD
Varian Unit at Apeksha Hospital is safe. Further, this study recommends to developing institutional CTV to PTV
margin for all sites of cancer to reduce unnecessary radiation to the surrounding normal healthy tissues. | en_US |
