RESUMO
Fiberoptic dosimetry (FOD) is an experimental technique suitable for in-vivo, real time dosimetry in radiotherapy treatments. FOD relies on using a small scintillator coupled to one end of a long optical fiber. The scintillator is placed at the point where the dose rate is to be determined whereas a light detector at the other end of the fiber measures the intensity of the radioluminescence emitted by the scintillator. One of the problems hampering the straightforward application of this technique in clinics is the presence of Cherenkov radiation generated in the fiber by the ionizing radiation, which adds to the scintillating light and introduces a bias in the dose measurement. Since Cherenkov radiation is more important in short wavelength range of the visible spectrum, using red-emitting scintillators as FOD detectors permits to reduce the Cherenkov contribution by using optical filters. In this work, the performance of red-emitting tellurium-doped zinc selenide crystal as FOD detector is evaluated and compared to the response of an ion-chamber.
Assuntos
Fibras Ópticas , Radiometria/métodos , Compostos de Selênio , Telúrio , Compostos de Zinco , Sistemas Computacionais , Tecnologia de Fibra Óptica , Humanos , Medições Luminescentes/métodos , Neoplasias/radioterapia , Radiocirurgia , Dosagem Radioterapêutica , Contagem de Cintilação/métodosRESUMO
A previous work concerning tumor control and skin damage in cutaneous melanoma treatments with BNCT has been extended to include doses, volumes and responses of 104 subcutaneous lesions from all patients treated in Argentina. Acute skin reactions were also scored for these patients, and cumulative dose-area histograms and dose-based figures of merit for skin were calculated. Broadening the tumor response analysis with the latest data showed that the (minimum or mean) tumor dose is not a good predictor of the observed clinical outcome by itself. However, when the tumor volume was included in the model as second explicative variable, the dose increases its significance and becomes a critical variable jointly with the volume (p-values<0.05). A preliminary analysis to estimate control doses for two groups of tumor sizes revealed that for small tumor volumes (< 0.1cm(3)) doses greater than 20 Gy-Eq produce a high tumor control (> 80%). However, when tumor volumes are larger than 0.1cm(3), control is moderate (< 40%) even for minimum doses up to 40 Gy-Eq. Some quantities based on skin doses, areas and complication probabilities were proposed as candidates for predicting the severity of the early skin reactions. With the current data, all the evaluated figures of merit derived similar results: ulceration is present among the cases for which these quantities take the highest values.
Assuntos
Terapia por Captura de Nêutron de Boro/efeitos adversos , Terapia por Captura de Nêutron de Boro/estatística & dados numéricos , Melanoma/radioterapia , Lesões por Radiação/etiologia , Neoplasias Cutâneas/radioterapia , Relação Dose-Resposta à Radiação , Eritema/etiologia , Humanos , Melanoma/patologia , Valor Preditivo dos Testes , Planejamento da Radioterapia Assistida por Computador/estatística & dados numéricos , Neoplasias Cutâneas/patologia , Úlcera Cutânea/etiologiaRESUMO
As part of phase I/II melanoma BNCT clinical trial conducted in Argentina in a cooperative effort of the Argentine Atomic Energy Commission (CNEA) and the Oncology Institute Angel H. Roffo (IOAHR), 7 patients (6 female-1 male) received eight treatment sessions covering ten anatomical areas located in extremities. Mean age of the patients was 64 years (51-74). The treatments were performed between October 2003 and June 2007. All patients presented multiple subcutaneous skin metastases of melanoma and received an infusion containing approximately 14 gr/m(2) of (10)borophenyl-alanine (BPA) followed by the exposition of the area to a mixed thermal-epithermal neutron beam at the RA-6 reactor. The maximum prescribed dose to normal skin ranged from 16.5 to 24 Gy-Eq and normal tissue administered dose varied from 15.8 to 27.5 Gy-Eq. Considering evaluable nodules, 69.3% of overall response and 30.7% of no changes were seen. The toxicity was acceptable, with 3 out of 10 evaluable areas showing ulceration (30% toxicity grade 3).
Assuntos
Terapia por Captura de Nêutron de Boro/métodos , Melanoma/radioterapia , Neoplasias Cutâneas/radioterapia , Idoso , Argentina , Compostos de Boro/uso terapêutico , Feminino , Humanos , Perna (Membro) , Masculino , Pessoa de Meia-Idade , Fenilalanina/análogos & derivados , Fenilalanina/uso terapêutico , Radiossensibilizantes/uso terapêutico , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por ComputadorRESUMO
A Phase I/II protocol for treating cutaneuos melanomas with BNCT was designed in Argentina by the Comisión Nacional de Energía Atómica and the medical center Instituto Roffo. The first of a cohort of thirty planned patients was treated on October 9, 2003. This article depicts the protocol-based procedure and describes the first clinical case, treatment regime and planning, patient irradiation, retrospective dosimetric analysis and clinical outcome. Considering the low acute skin toxicity and the complete response in 21 of the 25 subcutaneous melanoma nodules treated, a second irradiation was performed in a different location of the extremity of the same patient. The corresponding clinical outcome is still under evaluation.