| Περίληψη: | Volumetric Modulated Arc Therapy (VMAT) is a novel technique in radiotherapy, based on Intensity Modulated Radiation Therapy (IMRT), that enables simultaneous variation of gantry speed, collimator angle and dose rate, in order to change the field shape.
This study aims to evaluate and compare two different optimization methods used for VMAT plans in prostate cancer.
Nineteen prostate cancer cases were examined. Two different plans were created for each patient, using either biological or physical cost functions, provided by Monaco Treatment Planning System (TPS) (Elekta, Crawley, UK). Plan comparison was based on target coverage and surrounding healthy tissue protection, by utilizing dose-volume-histogram (DVH) outcomes, conformity index (CI) and homogeneity index (HI). Finally, patient specific quality assurance (psQA) took place to observe the deliverability and robustness of the two plans, in terms of three acceptance criteria (3%/2 mm, 2%/2 mm and 1%/1 mm). Outcomes of the two different plans were studied using the paired samples t-test with a threshold of p<0.05 for statistical significance.
In general, both of the plans were clinically acceptable. In both plans target dose coverage and homogeneity and conformity index, were comparable. Even though, the monitor units were more in the biological-based plan, this amount was not considerably high. On the other hand, in terms of OARs, in any structure and any dose level, the biologically optimized VMAT plan was significantly better (p<0.05). Finally, both of the plans passed with at least 98% the 3%/2 mm and 2%/2 mm acceptance criteria of gamma-analysis in psQA.
In conclusion, both of the plans create good target-coverage and they can be efficiently delivered. However, a superiority of the biological-based VMAT plan was observed in terms of OARs sparing.
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