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Independent verification of treatment planning system calculations

Dąbrowska-Szewczyk Edyta, Zawadzka Anna, Brzozowska Beata, Walewska Agnieszka, Kukołowicz Paweł

Nukleonika

2021

Vol. 66, No. 2

47--53

Purpose: According to the available international recommendations, at least one independent verifi cation of the calculations of number of monitor unit (MU) is required for every patient treated by teleradiotherapy. The aim of this study was to estimate the differences of dose distributions calculated with two treatment planning systems: Eclipse (Varian) and Oncentra MasterPlan (Elekta). Materials and methods: The analysis was performed for 280 three-dimensional conformal radiotherapy treatment (3D-CRT) plans with photon beams from Varian accelerators: CL 600C/D X6 MV (109 plans), CL 2300C/D X6 MV (43 plans), and CL 2300C/D X15 MV (128 plans). The mean doses in the planning target volume (PTV) and doses at the isocenter point obtained with Eclipse and Oncentra MasterPlan (OMP) were compared with Wilcoxon matched-pairs signed rank test. Additionally, the treatment planning system (TPS) calculations were compared with dosimetric measurements performed in the inhomogeneous phantom. Results: Data were analysed for 6 MV plans and for 15 MV plans separately, independently of the treatment machine. The dose values calculated in Eclipse were significantly (p <0.001) higher compared to calculations of OMP system. The average difference of the mean dose to PTV was (1.4 ± 1.0)% for X6 MV and (2.5 ± 0.6)% for X15 MV. Average dose disparities at the isocenter point were (1.3 ± 1.9)% and (2.1 ± 1.0)% for X6 MV and X15 MV beams, respectively. The largest differences were observed in lungs, air cavities, and bone structures. Moreover the variation in dosimetric measurements was less as compared to Eclipse calculations. Conclusions: OMP calculations were introduced as the independent MU verification tool with the first action level range equal to 3.5%.

Comparison of dose distributions in target areas and organs at risk in conformal and VMAT techniques and dose verifications with the use of thermoluminescence dosimetry

Paluch-Ferszt Monika, Kozłowska Beata, Dybek Marcin

Nukleonika

2020

Vol. 65, No. 4

217--222

The aim of the present study is to compare dose distributions and their verification in target areas and organs at risk (OAR) in conformal and volumetric modulated arc therapy (VMAT) techniques. Proper verification procedures allow the removal of the major sources of errors, such as incorrect application of a planning system, its insufficient or cursory commissioning, as well as an erroneous interpretation of the obtained results. Three target areas (head and neck, chest, and pelvic) were selected and the treatment was delivered based on plans made using collapsed cone convolution and Monte Carlo algorithms with 6-MV photon beams, adopting conformal and VMAT techniques, respectively. All the plans were prepared for the anthropomorphic phantom. Dose measurements were performed with TL detectors made of LiF phosphor doped with magnesium and titanium (LiF:Mg,Ti). This paper presents the results of TL measurements and calculated doses, as well as their deviations from the treatment planning system (TPS) in the three planned target areas. It was established that the algorithms subject to analysis differ, particularly in dose calculations for highly inhomogeneous regions (OAR). Aside from the need to achieve the dose intended for the tumour, the choice of irradiation technique in teleradiotherapy should be dictated by the degree of exposure toindividual critical organs during irradiation. While nothing deviated beyond the bounds of what is acceptable by international regulatory bodies in plans from TPS, clinically one must be more cautious with the OAR areas.

Wirtualna radioterapia – nowe narzędzie w procesie edukacji fizyków medycznych

Buliński Krzysztof, Kuszewski Tomasz, Wnuk Katarzyna, Kędzierawski Piotr, Braziewicz Janusz, Ślosarek Krzysztof

Inżynier i Fizyk Medyczny

2020

Vol. 9, nr 3

153--158

Fizyk medyczny to zawód, który wymaga umiejętności zastosowania metod fizyki w medycynie. Jeżeli dziedziną medycyny jest radioterapia, wówczas należy nauczyć się wykorzystania metod pomiarowych promieniowania jonizującego (dozymetria kliniczna) oraz informatyki (systemy planowania leczenia) w praktyce klinicznej. W procesie dydaktycznym wymagane jest wykorzystanie sprzętu medycznego, który jest w codziennym użytku. Pojawia się konflikt (pozorny), czy aparatura medyczna ma być wykorzystywana do celów edukacyjnych, czy też leczenia chorych. W okresie, kiedy informatyka i związana z nią technologia bardzo dynamicznie się rozwijają, kwestią czasu było pojawienie się wirtualnych akceleratorów, symulatorów. Rozwiązanie to bardzo ułatwia, z punktu widzenia organizacji pracy, proces szkolenia nie tylko fizyków medycznych, ale również lekarzy oraz elektroradiologów obsługujących aparaty terapeutyczne w radioterapii.

Medical physicist is a profession that requires the ability to apply physics methods in medicine. If the field of medicine is radiotherapy, then you should learn how to use radiation measurement methods (clinical dosimetry) and computer science (treatment planning systems) in clinical practice. The teaching process requires the use of medical equipment that is in use daily. There is a conflict (an apparent one) whether medical equipment is to be used for educational purposes or for treating patients. In the period when IT and related technology is developing very dynamically, it was just the matter of time when virtual accelerators, simulators appear. In such virtual reality we can use these programs to move virtual accelerator’s gantry, collimator... This solution greatly facilitates, from the point of view of work organization, the training process not only of medical physicists, but also doctors and technicians in radiotherapy.