ABSTRACT
BACKGROUND: Radiotherapy (RT) is frequently used in the treatment of head and neck cancer, but different side-effects are frequently reported, including a higher frequency of radiation-related caries, what may be consequence of direct radiation to dental tissue. The intensity-modulated radiotherapy (IMRT) was developed to improve tumor control and decrease patient's morbidity by delivering radiation beams only to tumor shapes and sparing normal tissue. However, teeth are usually not included in IMRT plannings and the real efficacy of IMRT in the dental context has not been addressed. Therefore, the aim of this study is to assess whether IMRT delivers lower radiation doses to dental structures than conformal 3D radiotherapy (3DRT). MATERIAL AND METHODS: Radiation dose delivery to dental structures of 80 patients treated for head and neck cancers (oral cavity, tongue, nasopharynx and oropharynx) with IMRT (40 patients) and 3DRT (40 patients) were assessed by individually contouring tooth crowns on patients' treatment plans. Clinicopathological data were retrieved from patients' medical files. RESULTS: The average dose of radiation to teeth delivered by IMRT was significantly lower than with 3DRT (p = 0.007); however, only patients affected by nasopharynx and oral cavity cancers demonstrated significantly lower doses with IMRT (p = 0.012 and p = 0.011, respectively). Molars received more radiation with both 3DRT and IMRT, but the latter delivered significantly lower radiation in this group of teeth (p < 0.001), whereas no significant difference was found for the other dental groups. Maxillary teeth received lower doses than mandibular teeth, but only IMRT delivered significantly lower doses (p = 0.011 and p = 0.003). Ipsilateral teeth received higher doses than contralateral teeth with both techniques and IMRT delivered significantly lower radiation than 3DRT for contralateral dental structures (p < 0.001). CONCLUSION: IMRT delivered lower radiation doses to teeth than 3DRT, but only for some groups of patients and teeth, suggesting that this decrease was more likely due to the protection of other high risk organs, and was not enough to remove teeth from the zone of high risk for radiogenic disturbance (>30Gy).
Subject(s)
Head and Neck Neoplasms/radiotherapy , Radiotherapy Dosage , Radiotherapy, Intensity-Modulated/methods , Tooth/radiation effects , Adolescent , Adult , Aged , Aged, 80 and over , Female , Head and Neck Neoplasms/complications , Humans , Imaging, Three-Dimensional/methods , Male , Middle Aged , Radiometry , Radiotherapy Planning, Computer-Assisted/methods , Retrospective Studies , Young AdultSubject(s)
Carcinoma, Squamous Cell/radiotherapy , Head and Neck Neoplasms/radiotherapy , Radiometry/methods , Tooth/radiation effects , Adult , Aged , Carcinoma, Squamous Cell/pathology , Female , Head and Neck Neoplasms/pathology , Humans , Male , Middle Aged , Neoplasm Staging , Radiotherapy Dosage , Radiotherapy, Conformal , Retrospective StudiesABSTRACT
OBJETIVO: Este trabalho foi realizado com o objetivo de caracterizar o detector de diamante, bem como observar seu comportamento. MATERIAIS E MÉTODOS: As características dosimétricas de feixes de fótons de 6 MV de energia foram medidas utilizando o sistema automático de varredura MP3 da PTW com um detector de diamante e foram comparadas com medidas usando uma câmara de ionização 31010 da PTW. RESULTADOS: As características dosimétricas do detector de diamante foram observadas por meio de medidas de linearidade com a dose, dependência com a taxa de dose e distribuições de dose em profundidade, bem como perfis. CONCLUSÃO: Algumas medidas com diamante e câmara de ionização foram validadas com resultados publicados na literatura, o que demonstrou um bom comportamento do detector de diamante na comparação com a câmara de ionização, muito utilizada para dosimetria em radioterapia, evidenciando que o diamante é uma boa escolha de detector para dosimetria de campos pequenos.
OBJECTIVE: The present study was aimed at characterizing a diamond detector and observing its behavior. MATERIALS AND METHODS: The dosimetric characteristics of 6 MV photon beams were measured by utilizing an automatic PTW MP3 scanning system with a diamond detector, and compared with measurements performed with a PTW 31010 ion chamber. RESULTS: Measurements of dose linearity, dose rate dependence and depth dose distribution as well as dose profiles demonstrated the dosimetric characteristics of the diamond detector. CONCLUSION: Some measurements with diamond detector and ion chamber were validated with results published in the literature, demonstrating a good behavior of the diamond detector as compared with the ionization chamber that is widely utilized for dosimetry in radiotherapy, indicating that the diamond detector is a good choice for small field dosimetry.
Subject(s)
Humans , Diamond , Dosimetry/methods , Radiotherapy/instrumentation , Diagnostic Techniques and Procedures/instrumentationABSTRACT
Os modernos marcapassos cardíacos podem falhar quando submetidos a radiaçäo ionizante da ordem de 10 Gy e exibir alteraçös funcionais com doses täo baixas quanto 2 Gy. A interferência eletromagnética também pode afetar seu desempenho, mas este efeito näo é problema sério quando consideramos os equipamentos de radioterapia atuais. Devido ao aumento significativo de aceleradores lineares no Brasil e, com isto, um aumento da probabilidade de tratamento de pacientes portadores de marcapassos cardíacos permanentes com esses equipamentos, apresentamos uma revisäo e discussäo dos problemas em potencial associados e sugerimos alguns cuidados que adotamos e praticamos no Serviço de Radioterapia do Hospital Israelita Albert Einstein
Subject(s)
Humans , Pacemaker, Artificial , Radiation, Ionizing , Radiotherapy, High-Energy/adverse effects , Fast Neutrons/adverse effects , Particle Accelerators , Radiography/adverse effects , Magnetic Resonance Spectroscopy/adverse effects , Risk FactorsABSTRACT
A reproduçäo diária precisa de um campo simulado e planejado é um aspecto essencial em radioterapia para o sucesso do tratamento. Neste trabalho, descrevem-se os seguintes problemas que podem influir na precisäo do posicionamento diário do paciente: movimento do paciente, marcas temporárias de pele e movimentos cardíaco e respiratório. Conclui-se que o componente do tratamento radioterapêutico mais sujeito a erros é a sua reprodutibilidade no dia-a-dia, e isto se deve às dificuldades de imobilizaçäo e mudanças físicas do próprio paciente. Assim, durante os procedimentos de planejamento, recomenda-se que o paciente seja simulado em uma posiçäo que seja reprodutível e confortável. Marcas na pele devem ser feitas de maneira clara, demarcando os planos transversal, coronal e sagital, a fim de permitir a definiçäo de volume de tratamento. Pelo menos sete marcas de pele säo necessárias para a definiçäo adequada desse volume. O técnico em radioterapia desempenha papel fundamental para o sucesso do tratamento, pois se este é preciso e cuidadoso permite maiores chances de um bom resultado final para o paciente
