Considerações sobre um aparato mecânico de implantes de sementes radioativas e de objeto anatômico simulador para experimentação em braquiterapia de próstata / Considerations on a mechanical apparatus for radioactive seed implantation and anatomical simulator object for prostate brachytherapy experimentation

O objetivo deste trabalho foi apresentar o estado da arte da pesquisa e desenvolvimento de um sistema mecânico de implante de sementes radioativas, denominado SISP, e de objeto anatômico simulador, OAS. O SISP e o OAS poderão auxiliar no procedimento de teste de implantes de sementes permanentes na próstata. Esses testes serão importantes para medições de doses absorvidas nas estruturas da pelve, envolvendo os órgãos e tecidos de risco para aprimoramento de planejamentos, posicionamentos de sementes e dosimetria.  O SISP envolve dois suportes, anterior e posterior, uma mesa-móvel, placa-guia. As peças foram elaboradas em celeron; enquanto a placa guia em acrílico translúcido. Após individualmente confeccionadas, as peças foram montadas, compondo o protótipo final do SISP. Foi também elaborado e montado o objeto anatômico simulador de teste (OAS), reproduzindo de forma anatômico-equivalente a estrutura óssea da pelve, parte do reto, próstata e tecido adiposo. Os materiais utilizados no objeto de teste são de tecido-equivalente, com equivalência radiológica. Este artigo apresenta o sistema acoplando o SISP e OAS acoplados, possível de uso em implantes experimentais para braquiterapia de próstata

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

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-3DCRT) 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 CAT3D 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

Development of a mouse computational model for MCNPx based on Digimouse (r) images and dosimetric assays

The aim of this study was to create and test a new mice 3D-voxel phantom named DM_BRA for mice and human first-estimation radiopharmaceutical dosimetry. Previously, the article reviews the state-of-art in animal model development. Images from Digimouse CT database were used in the segmentation and on the generation of the voxelized phantom. Simulations for validation of the DM_BRA model was performed at 0.015, 0.1, 0.5, 1 and 4 MeV photons with heart-source. Specific Absorbed Fractions (SAF) data were compared with literature data. The organ masses of DM_BRA correlated well with existing models based on the same dataset; however, few small organ masses hold significant variations. The SAF data in most simulated cases were statistically equal to a significant level of 0.01 to the reference data

Head and neck radiotherapy in patients with oral rehabilitation by dental implants: analysis of implant survival

Radiotherapy (RT) plays an important role in the treatment of patients with head and neck cancer. Clinical changes in the surrounding healthy tissue are often inevitable. The deleterious effects on the bones of the jaws have been considered a contraindication for rehabilitation with dental implants. However, in recent years, the installation of implants in irradiated patients has been consolidated as a valuable treatment option. The aim of this study was to evaluate the effect of RT on the survival of osseointegrated dental implants in patients with head and neck cancer. The applied methodology involved an electronic search in the MEDLINE database during the last five years.  We identified 67 scientific documents related to the keywords: "radiotherapy", "dental implants" and "head and neck cancer", four articles were selected and reviewed, composing this analysis.  It is concluded that dental implants installed in irradiated bone in the oral cavity have a high survival rate, 97.37%, provided that rigorous monitoring is instituted in RT in order to be successful in the long term. The percentage of dental implant failures tended to be higher in the group of irradiated patients