Determination of Intrafraction Laryngeal Movement in Radiotherapy
İsmail Faruk DURMUŞ1,Bora TAŞ1,Ömer Erol UZEL2
1Department of Radiation Oncology, Yeni Yüzyil Universty Gaziosmanpaşa Hospital, İstanbul-Turkey
2Department of Radiation Oncology, İstanbul Cerrahpaşa University Faculty of Medicine, İstanbul-Turkey
DOI : 10.5505/tjo.2020.2185 OBJECTIVE
Movement in early-stage laryngeal radiotherapy is an important factor in the success of the treatment. Thyroid cartilage may move by swallowing, breathing, sound production, and reflexes. During the treatment, the intra-fraction target movement was monitored by CBCT scans. In this study, we investigated the effects of laryngeal movement on the target volume.

CT scans were performed to 16 patients with maximum neck extension and treatment plans were prepared with VMAT fields with 6MV energy. CBCT scanning was performed to all patients before the treatment and necessary corrections were made. Then, simultaneous intrafraction CBCT scanning with the VMAT field was performed during the treatment. When the treatment field was over, the deviation amounts between CT and CBTC in the lateral, vertical and longitudinal axes were determined.

The deviation amount ? ±0.1cm was determined with 293 fractions in the lateral axis, 260 fractions in the vertical axis and 263 fractions in the longitudinal axis. Maximum deviation values were determined as 0.2 cm in the lateral axis, 0.5cm in the vertical axis and 0.5cm in the longitudinal axis. If the treatment has a 0.2cm CTV-PTV margin (for 305 fractions), treatment can be performed at a confidence interval of 100% on the lateral axis, 96.1% on the vertical axis and 94.1% on the longitudinal axis.

With the help of intra-faction monitoring, we are able to adjust the target margins and doses more precisely in laryngeal radiotherapy, especially for stereotactic treatment. To reduce possible movements in laryngeal radiotherapy, a maximum neck extension should be performed. Keywords : Intra-fraction motion; intra-fraction CBCT; laryngeal motion