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.
METHODS
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.
RESULTS
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.
CONCLUSION
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.