Dozimetrijska verifikacija kliničkog sistema za planiranje radioterapije
Sažetak
Uvod/Cilj. Poslednje dve decenije svedoci smo pojave novih tehnika radijacione terapije, sistema za planiranje tretmana (SPT) radioterapijom sa algoritmima za izračunavanje doze kod bolesnika, jedinica za višerednu (multislice) kompjuterizovanu tomografiju (KT) i slikom-vođeno praćenje. Cilj rada je bio da se utvrdi da li postoji značajna razlika u izračunavanju doze primenom SPT u odnosu na vrednosti dobijene merenjem na linearnom akceleratoru (LINAC), kao i razlika u tačnosti dozimetrijskog proračuna kalkulacionih algoritama Analytical Anisotropic Algorithm (AAA) i Acuros XB u zavisnosti od tipa tkiva i energije fotonskih snopova. Metode. Za End-to-End test koristili smo heterogeni fantom CIRS Thorax002LFC, koji anatomski odgovara ljudskom torzu sa setom umetaka poznate relativne elektronske gustine za dobijanje KT kalibracione krive, koja se poredi sa referentnim vrednostima, dobijenim CIRS 062M fantomom. Za AAA i Acuros XB algoritme kao i za 6 MV i 16 MV fotonske snopove u SPT Varian Eclipse 13,6, napravljena su četiri 3D konformalna (3DCRT), jedan intenzitetom modulisan (IMRT) i jedan zapreminski modulisan lučni (VMAT) plan radioterapije. Merenja apsolutne doze u mernim pozicijama Thorax fantoma, jonizacionom komorom PTW-Semiflex, sprovedena su na tri Varian-DHX LINAC-a. Rezultati. Razlika „referentne” i merene KT konverzione krive u oblasti kostiju bila je 3%. Od ukupno 476 mernih tačaka, razlika između izmerene i SPT izračunate doze od 3–6%, je nađena u 30 tačaka (6.3%). Regresionom analizom je utvrđen standardizovani koeficijent Beta za relativne greške, 6 MV vs. 16 MV, koji je iznosio 0,337 (33,7%, p < 0,001). Srednje vrednosti relativnih grešaka za AAA i Acuros XB za kosti, koristeći Mann-Whitney test, su bile 1,56% i 2,64% (p = 0,004). Zaključak. End-to-End test na Thorax002LFC fantomu je dao potvrdu ispravnog računanja doze primenom SPT u odnosu na dozu isporučenu pacijentu pomoću LINAC-a. Postojojala je značajna razlika između fotonskih energija relativnih grešaka (dobijene su veće vrednosti za 16 MV u odnosu na 6 MV). Utvrđena je statistički značajno manja relativna greška za kost kod AAA u odnosu na AcurosXB.
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