Assessment of the Impact of Inaccuracies in the Head and Neck Tumors Patient Positioning on the Halcyon Accelerator by the Amount of Dose-Volumetric Characteristics When Planning Radiotherapy

Abstract

Purpouse. To evaluate the impact of inaccuracies in patient positioning during irradiation of tumors in the head and neck region under the control of a portal imaging device on the Halcyon accelerator on the value of CTV-PTV offsets at the contouring stage.
 Material and methods. Treatment of patients and monitoring of the position of 35 patients on the therapeutic table using a portal visualization device during each irradiation session was carried out on a Halcyon tunnel-type electron accelerator, including an irradiation planning system (Eclipse version 16.1) and the Aria oncology information system (version 15.5).
 Resuits. Based on the results of positioning and analysis of a sample of 35 patients, it was concluded that it is possible to change the CTV-PTV offsets during contouring to a smaller side for the head area and a larger one for the neck area below the C3 vertebra. These results are explained by the strong fixation of the head in the thermoplastic mask, and the high mobility of the neck due to air gaps.
 Conclusions. When creating a treatment plan, changing the CTV PTV offsets leads to a reduction in the volume of the target and moving it away from critical structures. This makes it possible to increase the accuracy of the treatment and reduce the dose load on the normal tissues surrounding the tumor. The results obtained have high practical value.