Obsevanje dojke v globokem zadržanem vdihu: analiza intrafrakcijskih premikov : magistrsko delo

Jelovčan, Marjeta (avtor), Marinko, Tanja (mentor), Peterlin, Primož (komentor), But-Hadžić, Jasna (recenzent)

Uvod: Obsevanje raka dojke s tehniko globokega zadržanega vdiha zniža povprečno prejeto dozo na srce in pljuča. Sledenje intrafrakcijskih premikov je pomembno za vrednotenje morebitnega premikanja bolnika znotraj enega obsevanja. Namen: Namen raziskave je bil ovrednotenje intrafrakcijskih premikov s slikanjem CBCT pri obsevanju dojke ob uporabi tehnike globokega zadržanega vdiha s sistemom ABC in ovrednotenje obstoječega predpisanega varnostnega roba. Metode dela: V raziskavo je bilo vključeno 30 bolnic z rakom dojke, ki so se obsevale pooperativno s tehniko DIBH na obsevalnem aparatu Elekta Synergy Platform s sistemom ABC na Onkološkem inštitutu v Ljubljani v obdobju od oktobra 2020 do maja 2021. Za obsevalne tehnike 3DCRT ali IMRT smo uporabili vsakodnevno on-line slikanje CBCT pred obsevanjem za zmanjšanje interfrakcijskih premikov in po obsevanju za določitev intrafrakcijskih premikov. Dodatno slikanje tik po obsevanju smo izvajali prve tri dni obsevanja in nato dodatno enkrat na teden. Izvedli in analizirali smo 1050 premikov na 350 izvedenih CBCT v treh translacijskih smereh. Rezultati: Rezultati povprečnih intrafrakcijskih premikov pri vseh 30 bolnicah so znašali 0,03 cm ± 0,17 cm v longitudinalni smeri, -0,02 cm ± 0,13 cm v lateralni smeri in 0,07 cm ± 0,21 cm v vertikalni smeri. Porazdelitev povprečnih premikov za posamezne bolnice v longitudinalni, lateralni in vertikalni smeri ustrezajo Gaussovi krivulji normalne porazdelitve. V 175 slikanjih CBCT pred obsevanjem je pokazalo 40 premikov, večjih od 0,5 cm v longitudinalni smeri, kjer je največji znašal -1,4 cm inferiorno, 15 premikov v lateralni smeri z največjim -1,0 cm desno in 75 premikov v vertikalni smeri, kjer je bil največji -1,6 cm posteriorno. V 175 slikanjih CBCT po zaključenem obsevanju je pokazalo 3 premike, večje od 0,5 cm v longitudinalni smeri, kjer je bil največji -0,6 cm inferiorno, 1 premik v lateralni smeri, ki je meril -1,0 cm desno in 8 premikov v vertikalni smeri, kjer je bil največji -0,8 cm posteriorno. Rezultati velikosti varnostnih robov intrafrakcijskih premikov po Van Herkovi formuli so znašali 0,50 cm v longitudinalni smeri, 0,35 cm v lateralni smeri in 0,43 cm v vertikalni smeri, kar pomeni, da je prispevek intrafrakcijskih premikov k varnostnemu robu manjši od 0,5 cm varnostnega roba, ki ga uporabljamo v naši praksi. Razprava in zaključek: V raziskavi smo ugotovili, da so se bolnice kljub premikom, ki so nastali zaradi zadržanega vdiha med prvim in drugim zajemom slike pred in po obsevanju, kvalitetno in ustrezno obsevale, ker so izmerjene vrednosti ves čas ostale v predpisanih parametrih sistema ABC. Časovni intervali med začetnimi in kasnejšimi frakcijami niso vplivali na razlike v intrafrakcijskih premikih. Intrafrakcijski premiki so bili večji v začetnih frakcijah in so se zmanjševali tekom obsevanja, med nastavitvenim in verifikacijskim slikanjem CBCT pa so bili neodvisni od časa. Ocena varnostnega roba PTV naše raziskave ni pokazala, da je uporabljeni varnostni rob premajhen, ni pa odgovorila na to, ali je zadosten, ker nismo ocenjevali ostalih prispevkov k varnostnemu robu.

• Jezik: Slovenski jezik
• Ključne besede: magistrska dela, radiološka tehnologija, rak dojke, obsevanje v globokem zadržanem vdihu, sistem ABC, intrafrakcijski premiki
• Vrsta gradiva: Magistrsko delo/naloga
• Tipologija: 2.09 - Magistrsko delo
• Organizacija: ZF - Zdravstvena fakulteta
• Kraj izida: Ljubljana
• Založnik: [M. Jelovčan]
• Leto izida: 2022
• Št. strani: 50 str., [4] str. pril.
• PID: 20.500.12556/RUL-137442
• UDK: 616-07
• COBISS.SI-ID: 112023043
• Datum objave v RUL: 17.06.2022

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Breast irradiation in deep-inspiration breath-hold: analysis of intrafractional shifts : master thesis

Izvleček

Introduction: Breast cancer radiation therapy with deep-inspiration breath-hold reduces the mean radiation dose to the heart and lung. Intrafractional shift monitoring has great importance in assessing possible patient movement during treatment. Purpose: The research aim was to use CBCT imaging assess intrafractional shifts in DIBH technique with ABC system of breast radiation therapy and evaluation of the existing safety margin. Methods: 30 breast cancer patients were included in the study, which were treated post-surgically with DIBH technique on the accelerator Elekta Synergy Platform with ABC system at the Institute of Oncology Ljubljana from October 2020 until May 2021. For 3DCRT and IMRT techiques we used daily on-line CBCT imaging before treatment to reduce interfractional shifts and after irradiation for evaluation of intrafractional shifts. Additional imaging after irradiation was performed over the first three fractions of radiotherapy, then additionally once a week. We obtained and analyzed 1050 shifts in 350 on-line CBCT imaging in three translation directions. Results: Mean intrafractional shifts for all 30 patients were 0,03 ± 0,17 cm in the longitudinal direction, -0,02 cm ± 0,13 cm in the lateral direction and 0,07 cm ± 0,21 cm in the vertical direction. Our study of mean shifts contribution showed that mean distribution of longitudinal, lateral and vertical directions comply with the Gaussian distribution. 175 CBCT imaging before irradiation showed 40 shifts in the longitudinal direction with a maximum of -1,4 cm inferior, 15 shifts in the lateral direction with a maximum of -1,0 cm right and 75 shifts in the vertical direction with a shift of -1,6 cm posterior. 175 post-irradiation CBCT images after irradiation showed 3 shifts in the longitudinal direction with a maximum of -0,6 cm inferior, 1 shift in the lateral direction which shifted -1,0 cm to the right and 8 shifts in the vertical direction with a maximum of -0,8 cm posterior. The contribution of the intrafractional shifts to the safety margins according to Van Herk’s formula were 0,50 cm in the longitudinal direction, 0,35 cm in the lateral direction and 0,43 cm in the vertical direction, which means that they are smaller than 0,5 cm margin we use in our practice. Discussion and conclusion: We concluded the patient motion during the deep inspiration treatment was within the tolerances and the patients were treated correctly. Time intervals between starting and later fractions did not have an impact on intrafractional shift differences. Intrafractional shifts were larger in starting fractions and decreased during irradiation and were irrelevant within set-up and verification CBCT imaging. Estimated safety margin for the PTV in our study did not show that the safety margin in use is too small, as we did not evaluate other factors contributing to it in this study, we cannot give a definite answer about its sufficiency.

• Ključne besede: master's theses, radiologic technology, breast cancer, deep-inspiration breath-hold radiation therapy, ABC system, intrafractional shifts