ESTRO 2021 Abstract Book

S1351

ESTRO 2021

Material

Actual composition

Actual

mass

RayStation model

RayStation mass density (gr/cm 3 )

density (gr/cm 3 )

Titanium prosthesis

Ti 87% Al 6% Nb 7% Cr 28% Co 66% Mb 6% H 7.5% C 85.5% N 5.3% O 1.6% S 0.1%

4.52

Ti 100%

4.45

Cobalt Chrome prosthesis

8.28

Steel 100%

8.11

ABS resin

1.193

H 7.6% C 90.4% O 0.8% Ti 1.2%

1.2

In the case of the ABS resin, we tested and compared several RayStation materials: adipose, PlasticTE A-150, and RW3. Results Titanium prosthesis had a measured WET of 3.18 (the calculated value was 3.23). Modeling it as pure Titanium with density reproduced accurately the WET. Co-Cr prostheses measured WET was 5.79 (calculated value was 5.85). Its modeling as steel properly reproduced its WET, as well as the proton scatter and the nuclear reactions. ABS resin was best modeled using RW3 among the three compounds, achieving very good agreement in WET, proton scatter and nuclear reactions. RW3 and especially A-150 reproduced both very well the proton scattering, but nuclear cross sections for RW3 resembled much better than the other two compounds those from ABS . This material the one that shows the smallest difference in dose . Conclusion A Monte Carlo comparison of the nuclear cross sections and proton scatter for the actual and modelled metallic and synthetic materials ensured the accuracy of RayStation dose calculations in the patients we have treated. Monte Carlo was very helpful to compare and deem which compound in the RayStation database fits best the actual ABS resin. PO-1630 FilmQADog: a free alternative for film dosimetry analysis. C.D. Contreras Quiroz 1,2 1 Universidad de los Andes, Departamento de Física, Bogotá D.C, Colombia; 2 Centro de Control de Cáncer, Física Médica, Bogotá D.C, Colombia Purpose or Objective Radiochromic film dosimetry has become important tool for quality assurance at high-resolution 2D map dose verification of treatment plans, principally due to its desirable properties as a dosimeter and the relatively simple setup for irradiation and processing. However, the absence of an open source software for film analysis limits the routine use of this QA technique, especially in less developed countries, where economic resources for acquiring specialized software are tight. Aiming to overcome this limitation, FilmQADog, an open source Python based software for radiochromic film analysis was developed. Materials and Methods FilmQADog was generated using the Python programming language, making use of WxPython library for the GUI design. Furthermore, digital image handling was performed with free available libraries such as scki-kit image, tiffread, pymedphys, pydicom, numpy, scipy and matplotlib. Hence, the resulting software is an open source project ready for being used by everyone who wants to perform quality assurance with film dosimetry, allowing source modification to add new utilities. Results The main functionalities of FilmQADog include the generation of various calibration functions, including self- defined ones, film digitalization filtering and noise reduction, generation of 2D dose maps (Figure 1) with single and multichannel methods and tools for plan-to-film comparison using DICOM RT files from the TPS, including Γ analysis (Figure 2) and several visualization options. The software was tested by use of simple field geometry plans like square irradiation and pyramidal plans, as well as IMRT plans. Functionality was further verified by comparison with a commercially available software, obtaining concordance with each test performed.