RESUMO
A dosimetry intercomparison between the boron neutron capture therapy groups of the Massachusetts Institute of Technology (MIT) and the Comisión Nacional de Energía Atómica (CNEA), Argentina was performed to enable combined analyses of NCT patient data between the different centers. In-air and dose versus depth measurements in a rectangular water phantom were performed at the hyperthermal neutron beam facility of the RA-6 reactor, Bariloche. Calculated dose profiles from the CNEA treatment planning system NCTPlan that were calibrated against in-house measurements required normalizations of 1.0 (thermal neutrons), 1.13 (photons), and 0.74 (fast neutrons) to match the dosimetry of MIT.
Assuntos
Terapia por Captura de Nêutron de Boro/estatística & dados numéricos , Terapia por Captura de Nêutron de Boro/normas , Radiometria/estatística & dados numéricos , Argentina , Calibragem , Humanos , Massachusetts , Radiometria/normas , Dosagem Radioterapêutica , Valores de Referência , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
This work evaluates the performance of two NCT treatment planning systems: NCTPlan, developed by the CNEA and the Harvard-MIT group, and SERA, developed by the INEEL/Montana State University group. The study was performed in some simple geometries with the therapeutical hyperthermal beam of the RA-6 facility at Bariloche, Argentina. The first geometry was a rectangular phantom and calculations and measurements were made along the central beam axis and along a parellel axis, 4 cm apart from the central beam axis. Measurements and calculations were also performed in a cylindrical phantom, to explore the behavior of the treatment planning systems in a geometry simulating an extremity, in accordance with the CNEA clinical protocol. Comments on differences in source definitions and cross sections libraries are also included in the text. It can be seen that both codes give acceptable results on the central beam axis and on a lateral axis, showing good agreement with experimental results.
Assuntos
Terapia por Captura de Nêutron de Boro/instrumentação , Planejamento da Radioterapia Assistida por Computador , Argentina , Terapia por Captura de Nêutron de Boro/métodos , Terapia por Captura de Nêutron de Boro/estatística & dados numéricos , Nêutrons Rápidos/uso terapêutico , Humanos , Imagens de Fantasmas , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/estatística & dados numéricosRESUMO
Irregular fields for boron neutron capture therapy (BNCT) have been already proposed to spare normal tissue in the treatment of superficial tumors. This added dependence would require custom measurements and/or to have a secondary calculation system. As a first step, we implemented the sector-integration method for irregular field calculation in a homogeneous medium and on the central beam axis. The dosimetric responses (fast neutron and photon dose and thermal neutron flux), are calculated by sector integrating the measured responses of circular fields over the field boundary. The measurements were carried out at our BNCT facility, the RA-6 reactor (Argentina). The input data were dosimetric responses for circular fields measured at different depths in a water phantom using ionisation and activation techniques. Circular fields were formed by shielding the beam with two plates: borated polyethilene plus lead. As a test, the dosimetric responses of a 7x4 cm(2) rectangular field, were measured and compared to calculations, yielding differences less than 3% in equivalent dose at any depth indicating that the tool is suitable for redundant calculations.
Assuntos
Terapia por Captura de Nêutron de Boro/estatística & dados numéricos , Planejamento da Radioterapia Assistida por Computador/estatística & dados numéricos , Argentina , Terapia por Captura de Nêutron de Boro/instrumentação , Humanos , Neoplasias/radioterapia , Imagens de Fantasmas , Eficiência Biológica RelativaRESUMO
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.
Assuntos
Terapia por Captura de Nêutron de Boro , Frutose/análogos & derivados , Melanoma/radioterapia , Neoplasias Cutâneas/radioterapia , Argentina , Boro/sangue , Boro/farmacocinética , Compostos de Boro/farmacocinética , Compostos de Boro/uso terapêutico , Terapia por Captura de Nêutron de Boro/métodos , Protocolos Clínicos , Feminino , Frutose/farmacocinética , Frutose/uso terapêutico , Humanos , Melanoma/metabolismo , Melanoma/secundário , Pessoa de Meia-Idade , Planejamento da Radioterapia Assistida por Computador , Neoplasias Cutâneas/metabolismo , Neoplasias Cutâneas/secundário , Resultado do TratamentoRESUMO
This article reports on the progress of the modeling and experimental characterization of the RA-6 reactor neutron beam, designed for the upcoming BNCT clinical trials of skin melanoma, and presents the first theoretical analysis of such beam performance. The aspects relating to surface source modeling and assessment, beam dosimetry, treatment planning system calibration, and treatment planning optimization are presented herein. Several methods and criteria were established in order to provide guidance for future clinical studies conducted in this facility. Following a realistic model, the theoretical analysis was based on a clinical case of malignant melanoma in extremities. Owing to the complex geometry of the tumor, this particular clinical case represents one of the most difficult lesions to be treated. This article discusses the thorough evaluation stage that has led to the optimization of the treatment planning procedure. Two candidate plans were proposed, and dose-volume distributions in the target volume were evaluated on the basis of the application of a series of criteria that define the critical normal structures which limit the dose delivered. In spite of the complexity of the clinical case under review, results showed that only 4% of the tumor volume is underdosed in cases of mean blood 10B concentration values, even in the most unfavorable analysis. The overall results suggest that this BNCT facility is prepared to rigorously explore the clinical efficacy of the RA-6 beam and the BNCT treatment modality for peripheral melanomas.