Optimizacija obsevanja možganskih tumorjev za določitev varnostnega roba pri sodobnih tehnikah obsevanja : magistrsko delo

Dolenc, Laura (author), Smrdel, Uroš (mentor), Žager Marciuš, Valerija (comentor), Mekiš, Nejc (reviewer)

Uvod: Možgani so kompleksen organ, ki ob pojavu raka, kot ene najtežjih bolezni v današnji dobi, niso ostali ne prizadeti. Glede na to iz kakšnih celic so možganski tumorji sestavljeni, ločimo primarne in sekundarne tumorje. Zelo pomembno vlogo pri zdravljenju le teh ima radioterapija, kjer se za obsevanje uporabljajo megavoltni fotonski žarki energije 6 megavoltov, tridimenzionalne tehnike obsevanja in sistem slikovno vodene radioterapije. Velikost varnostnega roba pri obsevanju možganov znaša do 2 cm. Namen: Preveriti ali obstoječi varnosti rob kliničnega ciljnega volumna in načrtovanega tarčnega volumna ustreza izračunanemu varnostnemu robu za obsevanje možganov ter definirati varnostne robove potrebne za obsevanje posameznih regij možganov. Metode dela: Na Onkološkem inštitutu Ljubljana smo izvedli presečno retrospektivno raziskavo. Izbrali smo si časovno obdobje enega leta in sicer od 1. 9. 2018 do 1. 9. 2019. V elektronskih/fizičnih obsevalnih kartonih bolnikov, smo glede na lokacijo tumorja, pregledali sistematične napake in na podlagi teh, izračunali povprečne sistematične napake in velikosti varnostnih robov glede na možganski reženj ter naredili primerjavo z že obstoječimi varnostnimi robovi. Podatke smo analizirali s programom za statistično obdelavo. Rezultati: Povprečne sistematične napake glede na možganske regije smo izračunali v štirih smereh: lateralni, longitudinalni, vertikalni in v smeri rotacije. Največjo sistematično napako v lateralni smeri smo izračunali v področju cerebelarno, ki je tudi statistično značilna (p < 0,05). V longitudinalni in vertikalni smeri pri nobeni od regij nismo zaznali statistično značilnih razlik. Smo pa statistično značilno razliko zaznali v smeri rotacije in sicer v frontalnem režnju (p=0,037) in legi tumorja cerebelarno (p=0,002). Največjo velikost varnostnega roba smo izračunali za tumorje, ki ležijo cerebelarno (0,80 mm), medtem ko bi tumorjem v področju parietalnega režnja dodali zgolj 0,31 mm velik varnostni rob. Z linearno regresijo smo ugotovili tudi, da na lateralne premike in rotacijo vpliva zgolj lega tumorja cerebelarno (p < 0,05), medtem ko na longitudinalne in vertikalne premike ne vpliva nobeden izmed faktorjev. Razprava in zaključek: Ugotovili smo, da so velikosti povprečnih sistematičnih napak manjše od velikosti 1 mm, kar lahko pripišemo dobri fiksaciji bolnikov s tri točkovno termoplastično masko. Glede na izračun varnostnega roba (klinični ciljni volumen in planirani tarčni volumen), bi tako varnostni rob iz obstoječih 5 mm zmanjšali na 2-3 mm, v kolikor bi v procesu obsevanja sledili protokolu portalnega slikanja.

• Language: Slovenian
• Keywords: magistrska dela, radiološka tehnologija, možganski tumorji, radioterapija, sodobne tehnike obsevanja, geometrična verifikacija obsevanja, varnostni rob pri obsevanju možganov
• Work type: Master's thesis/paper
• Organization: ZF - Faculty of Health Sciences
• Place of publishing: Ljubljana
• Publisher: [L. Dolenc]
• Year: 2021
• Number of pages: 39 str., [2] str. pril.
• PID: 20.500.12556/RUL-144675
• COBISS.SI-ID: 79165443
• Publication date in RUL: 07.03.2023

DOLENC, Laura, 2021, Optimizacija obsevanja možganskih tumorjev za določitev varnostnega roba pri sodobnih tehnikah obsevanja : magistrsko delo [online]. Master’s thesis. Ljubljana : L. Dolenc. [Accessed 25 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=144675

Secondary language

• Language: English
• Title: Optimization of brain tumors irradiation, determinig the set-up margin in modern irradiation techniques : master thesis

Abstract

Introduction: The brain is a complex organ that coordinates the activity of all functions, but in the occurrence of cancer, these have not remained intact. Considering what cells brain tumors are made of, we distinguish between primary and secondary brain tumors. An important part of medical treatment is radiation therapy, which uses megavoltage photon beams, three-dimensional radiation techniques, and the image-guided radiation therapy system. The size of the margins used in radiotherapy of the brain is up to 2 cm. Purpose: The purpose of this thesis was to evaluate whether the excising margin of the clinical tumor volume and planning target volume correspond with calculated radiation margin based on systematic errors and to define radiation margins required for irradiation of individual brain lobes. Methods: A retrospective cross-sectional study was performed at the Institute of Oncology Ljubljana. We chose a period of one year, from September 1, 2018 to September 1, 2019. In the patient's electronic/physical irradiation maps, we checked the systematic errors and calculated their average and the size of radiation margins, both divided by brain lobe. We compared them with the existing ones. The data were statistically analyzed using a statistical data processing program. Results: We calculated the average systematic errors in four directions: lateral, longitudinal, vertical and rotation. The largest average systematic error was calculated in the lateral direction in the cerebellar area, and the error was also statistically significant (p < 0.05). In longitudinal and vertical direction, we did not find statistically significant differences between brain lobes. In rotational direction we notice the statistically significant difference in frontal lobe (p=0.037) and cerebellar area (p=0.002). The largest radiation margin was calculated for tumors in the cerebellar area (0.80 mm), while for tumors in the parietal lobe the calculated margin was only 0.31 mm. Using linear regression, we found that for lateral movements and rotation, only the position of the tumor in the cerebellar area was statistically significant (p < 0.05), while longitudinal and vertical movements were not affected by any of the factors. Discussion and conclusion: We found that the magnitude of the average systematic errors is less than 1 mm. The reason may be the fixation of patients with three-point fixation masks. Depending on the calculated irradiation boundary (clinical tumor volume and planned target volume), the boundary can be reduced from the existing size of 5 mm to a size between 2 and 3 mm if the portal imaging protocol is followed during irradiation.

• Keywords: master's theses, radiologic technology, brain tumors, radiotherapy, modern radiation therapy techniques, geometric verification of radiation, radiation treatment margin