EP-1790: Assessment of Uterine Fundus Coverage with IGRT using daily CBCT in cervical cancer
Z. Özen, Namık Kayalılar, Alptekin Arifoğlu, B. Günhan, R. Ibrahimov, F. Karaköse, S. Gurdall, Mehmet Ufuk Abacioglu · Radiotherapy and Oncology · 2016
Material and Methods: 50 consecutive head and neck cancer treatments with IMRT were analyzed.Lorca Marin customized masks named Nature were used to immobilize head and neck.These 2-oxepanone polymer thermoplastic masks are 3-points immobilization with frontal and mental reinforcement and 3.2 mm thickness.3-standard references were marked on the surface of the mask and on the middle chest of the patient for accurate positioning every day.Cone-beam computed tomography scan to verify online the position was performed during 5 consecutive days and after, weekly cone-beam (CBCT) until the end of the treatment.After weekly matching process using automated soft-tissue registration, translational movements along the three axes (x, y, z) were collected and the average for each treatment and each axis was calculated.Displacement´s mean of the 50 averages and the standard deviations were analyzed and compared.Results: The resulting displacement average after analyzing 50 treatments was less than 1 mm along the three axes: x = (0.62±0.51) mm, y = (0.83±0.63) mm, z = (0.65±0.59) mm.These setup displacements have remained under 3 mm in 100% of treatments.These results achieve the International Commission on Radiation Units and Measurements recommendations regarding the setup margin to compensate the immobilization and positioning errors. Conclusion:The type of patient immobilization devices and their contribution in the setup errors must be taken into account for IMRT.Additionally, the use of different imageguidance systems can significantly alter the size of the required margins.Lorca Marin thermoplastics masks with weekly CBCT show enough accuracy and stability for IMRT head and neck cancer patients. EP-1789 Immobilization and dosimetric performance of a MRI compatible frame for head and neck patients A. Perez-Rozos