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Analysis of deviations in the localization of radiation fields in the course of radiation by means of EPID in patients with tumours in head and neck
GRABMÜLLEROVÁ, Hana
Oncology diseases are serious and alarming problems in the world and our country, too. The most common ENT tumours affect larynx, oropharynx and hypopharynx. The factor which causes the occurrence of tumours is smoking. Chronic thermal excitation, pH changes of mucous membrane and vasoconstriction caused by nicotine can also participate in the occurrence of malign changes. Among other etiological factors belong: alcohol, U radiation, ionizing radiation, transport and industry exhalations, nutritional exhaustion, and immunodeficiency. Current treatment includes surgery, radiotherapy, cytostatic chemotherapy, hormone therapy, bio therapy and their combinations. The prosperity of oncology patients is 22% by surgery, 18 % by radiotherapy and 5% by chemotherapy. Radio therapy remains the basic treatment of oncology diseases. According to the newest knowledge and requests its quality is ensured. The accuracy of radiation treatment and the increases in therapeutic results are developed. The risk of over dosing, which leads to the occurrence of many complications, and also the risk of under dosing, which decreases the chance of the complete cure, decline. Quality assurance is currently carried out on electronic portal image device EPID (Electronic Portal Imaging). The reason of permitted small deviation (0,3cm) in tumours of head and neck is the proximity of critical organs to the target volume and often small radiated volumes. The aim of the thesis was the analysis of the group of patients with the tumours of head and neck treated at oncology department in Nemocnice České Budějovice, a.s. (Hospital in České Budějovice Inc.) by the form of portal evaluation. The hypothesis was average deviation 0,3cm in localization of radiated fields in the evaluated group. The analysis of deviations in localization of radiation fields in the course of radiation of evaluated group was carried out. The gained deviations were compared with the data in professional literature. The methodology included the characteristics of evaluated group of patients according to radiation posture, fixation of a patient, radiation technique, localization of tumour, the extent of disease TNM, patient´s age and sex-a man, a woman. The evaluation was carried out by means of EPID for particular radiation fields. Statistically, maximum, minimum and average deviation in localization of radiation fields was evaluated and the results were compared with the hypothesis by means of the test {$\psi$}2. The presupposed hypothesis was not proved. From the measured data it was found out that in practice acquired deviations are smaller than deviations presupposed by the hypothesis. The important part of radio therapeutic practice is the programme of Quality Assurance (QA). The results will serve the workers of radiation oncology in Nemocnice České Budějovice, a.s. (Hospital in České Budějovice Inc.) for evaluation of radiotherapy quality in the tumours of head and neck.
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Quality assurance IMRT plans
LOŠKOVÁ, Michaela
We may regard the Intensity-Modulated Radiation Therapy (IMRT) as a break-through and progress concerning the treatment of oncogenous diseases. In practice, this new method experienced an extensive development as early as at the end of 1990s. At the present time, the IMRT is a medical treatment used in an increasingly frequent manner. It concerns predominantly such oncogenous diseases, the treatment of which based on the above-mentioned method is applicable due to the localization of the disease. The IMRT enables a more effective distribution of a dose in the target volume than in case of the conventional radiotherapy. It is also possible to realize maximum treatment of the surrounding healthy tissues. For the purpose of clinical use of the IMRT, however, it is necessary to verify the correspondence between the dose planned and the dose actually realized in the target volume. From the large quantity of correspondence verification methods available, I decided to select the three following ones to be covered in this paper: - portal dosimetry method - measurement using special phantom - measurement using 2D filed of the Seven29 detectors. The goal of my work was to compare these three methods of verification of the IMRT plans and in addition, to verify the applicability of the 3% tolerance criterion for all the above-mentioned methods of verification. The portal dosimetry method is applicable for verification of fluency; it is fully sufficient and not time-consuming for the purpose of clinical use. The measurement using 2D field provides for sufficiently accurate information on a dose{\crq}s distribution in the modulated field, however, it is more time-consuming and the measuring device is not integrated in the system of the radiation apparatus. Verification using special phantom is considerably time-consuming and it provides for information on a dose{\crq}s distribution in a small quantity of points. The DD=3% criterion I selected is applicable to all three methods with the exception of areas with extensive modulation of the dose and areas on the verge of the field.
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