| Abstract [eng] |
Dosimetric measurement is a vital component for clinical procedures, especially for Intensity-Modulated Radiotherapy and Volumetric Modulated Arc radiotherapy. These procedures require the use of tailored phantoms for quality assurance, which has a variety of shortcomings such as homogenous materials unable to mimic the true radiation attenuation properties of the human body. The SHANE phantom is introduced to tackle these shortcomings and the purpose of this thesis is to perform an accurate dosimetric evaluation with phantom SHANE for head and neck cancer. The experiment was performed using two medical linear accelerators Elekta infinity (Monaco TPS) and Varian Halcyon (Eclipse TPS) at Siauliai Hospital department of radiotherapy and Onkologinė ligoninė, Volungių g. 16, Kaunas respectively with photon energy 6 MeV (max). The ion chamber, electrometer, and SHANE phantom are the main equipment used. Different MLC field size tests, in-plane, and cross-plane profile tests were performed in the treatment planning system using virtual water phantom. The treatment planning system was done for VMAT delivery technique with simultaneous integrated boost (SIB) using Monaco treatment planning system (TPS) for linear accelerator (LA) Electra infinity and LA Eclipse for Halcyon. Three PTV (PTV_7000, PTV_6000, and PTV_5400) was assigned the dose 70 Gy, 60 Gy, and 54 Gy respectively with 30 fraction and spinal cord as organ at risk. The patient-specific quality assurance was performed using the Octavius detector. The dose difference for ion chamber measurement and treatment planning calculated dose using Eclipse TPS for (all four points of measurement IC_PTV_7000 (1.13 % ), IC_PTV_6000(1.34 %), IC_ PTV_5400 (1.06 %), and for IC_spinal cord (2.95 %) are within the tolerance limit of 5% for PTVs and 7% the organ at risk spinal cord. Similar tendency was observed for the LA Halcyon: IC_PTV_7000 (12.85 %), IC_PTV_6000 (1.60 %) and IC_ PTV_5400 (3.05 %) and for IC_spinal cord (2.57 %) are within the tolerance limit of 5 %-7%, except IC PTV 7000. |
