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. 2021 Apr 14;26(2):242-250.
doi: 10.5603/RPOR.a2021.0037. eCollection 2021.

Dose measurements in a thorax phantom at 3DCRT breast radiation therapy

Elsa Bifano Pimenta  1 , Luciana Batista Nogueira  2 , Tarcísio Passos Ribeiro de Campos  1
Affiliations

Dose measurements in a thorax phantom at 3DCRT breast radiation therapy

Elsa Bifano Pimenta et al. Rep Pract Oncol Radiother. .

Abstract

Background: The anthropomorphic and anthropometric phantom developed by the research group NRI (Núcleo de Radiações Ionizantes) can reproduce the effects of the interactions of radiation occurring in the human body. The whole internal radiation transport phenomena can be depicted by film dosimeters in breast RT. Our goal was to provide a dosimetric comparison of a radiation therapy (RT) plan in a 4MV 3D-conformal RT (4MV-3DCR T) and experimental data measured in a breast phantom.

Materials and methods: The RT modality was two parallel opposing fields for the left breast with a prescribed dose of 2.0 Gy in 25 fractions. The therapy planning system (TPS) was performed on CA T3D software. The dose readings at points of interest (POI) pre-established in TPS were recorded. An anthropometric thorax-phantom with removal breast was used. EBT2 radiochromic films were inserted into the ipisilateral breast, contralateral breast, lungs, heart and skin. The irradiation was carried out on 4/80 Varian linear accelerator at 4MV.

Results: The mean dose at the OAR's presented statistically significant differences (p < 0.001) of 34.24%, 37.96% and 63.47% for ipsilateral lung, contralateral lung, and heart, respectively. The films placed at the skin-surface interface in the ipsilateral breast also showed statistically significant differences (p < 0.001) of 16.43%, -10.16%, -14.79% and 15.67% in the four quadrants, respectively. In contrast, the PTV dosimeters, representative of the left breast volume, encompassed by the electronic equilibrium, presented a non-significant difference with TPS, p = 0.20 and p = 0.90.

Conclusion: There was a non-significant difference of doses in PTV with electronic equilibrium; although no match is achieved outside electronic equilibrium.

Keywords: breast cancer; radiochromic film; thorax phantom.

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Conflict of interest statement

Conflict of interests The authors declare that there is no conflict of interests regarding the publication of this paper.

Figures

Figure. 1
Figure. 1
The films BS1, BS2, BS3 and BS4 placed in each quadrant on ipsilateral breast skin (A). The organ at risk (OAR) films were inserted in the two lungs and in the heart myocardium (B). The planning target volume (PTV) films (M1, M2, M3 and M4) were inserted into the ipsilateral breast of thorax phantom (C) along the axial axis (D)
Figure 2
Figure 2
The 3D-conformal radiotherapy (3D-CRT) plan performed in CA T3D based on axial images registered by the CT. Images were superposed to the axial CT image sections, and a sagittal reconstruction was performer
Figure 3
Figure 3
Spatial dose maps generated within M1 (A), M2 (B), M3 (C) and M4 (D) dosimeters placed in the left-breast exposed with the 3D-conformal radiotherapy (3D-CRT), in which XY-scales were in mm and dose scale in Gy
See this image and copyright information in PMC

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