RESUMO
In this work we provide some information on the present status of accelerator-based BNCT (AB-BNCT) worldwide and subsequently concentrate on the recent accelerator technology developments in Argentina.
Assuntos
Terapia por Captura de Nêutron de Boro/instrumentação , ArgentinaRESUMO
The activity in accelerator development for accelerator-based BNCT (AB-BNCT) both worldwide and in Argentina is described. Projects in Russia, UK, Italy, Japan, Israel, and Argentina to develop AB-BNCT around different types of accelerators are briefly presented. In particular, the present status and recent progress of the Argentine project will be reviewed. The topics will cover: intense ion sources, accelerator tubes, transport of intense beams, beam diagnostics, the (9)Be(d,n) reaction as a possible neutron source, Beam Shaping Assemblies (BSA), a treatment room, and treatment planning in realistic cases.
Assuntos
Terapia por Captura de Nêutron de Boro/instrumentação , Aceleradores de Partículas/instrumentação , Radiometria/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , Internacionalidade , Avaliação da Tecnologia BiomédicaRESUMO
We describe the present status of an ongoing project to develop a Tandem-ElectroStatic-Quadrupole (TESQ) accelerator facility for Accelerator-Based (AB)-BNCT. The project final goal is a machine capable of delivering 30 mA of 2.4 MeV protons to be used in conjunction with a neutron production target based on the (7)Li(p,n)(7)Be reaction. The machine currently being constructed is a folded TESQ with a high-voltage terminal at 0.6 MV. We report here on the progress achieved in a number of different areas.
Assuntos
Terapia por Captura de Nêutron de Boro , Terapia por Captura de Nêutron de Boro/instrumentação , Eletricidade EstáticaRESUMO
In this work we describe the present status of an ongoing project to develop a tandem-electrostatic-quadrupole (TESQ) accelerator facility for accelerator-based (AB) BNCT at the Atomic Energy Commission of Argentina in Buenos Aires. The project final goal is a machine capable of delivering 30 mA of 2.4 MeV protons to be used in conjunction with a neutron production target based on the (7)Li(p,n)(7)Be reaction slightly beyond its resonance at 2.25 MeV. These are the specifications needed to produce sufficiently intense and clean epithermal neutron beams, based on the (7)Li(p,n)(7)Be reaction, to perform BNCT treatment for deep-seated tumors in less than an hour. An electrostatic machine is the technologically simplest and cheapest solution for optimized AB-BNCT. The machine being designed and constructed is a folded TESQ with a high-voltage terminal at 1.2 MV intended to work in air. Such a machine is conceptually shown to be capable of transporting and accelerating a 30 mA proton beam to 2.4 MeV. The general geometric layout, its associated electrostatic fields, and the acceleration tube are simulated using a 3D finite element procedure. The design and construction of the ESQ modules is discussed and their electrostatic fields are investigated. Beam transport calculations through the accelerator are briefly mentioned. Likewise, work related to neutron production targets, strippers, beam shaping assembly and patient treatment room is briefly described.
Assuntos
Terapia por Captura de Nêutron de Boro/instrumentação , Aceleradores de Partículas , Argentina , Fenômenos Biofísicos , Neoplasias Encefálicas/radioterapia , Arquitetura de Instituições de Saúde , Humanos , Eletricidade EstáticaRESUMO
Microdistributions of the prospective BNCT-compound CuTCPH, a carborane-containing tetraphenylporphyrin with one Cu atom in its molecular structure, have been obtained in tissue sections of different organs of tumor-bearing and normal Syrian hamsters injected with the boron compound by employing a heavy ion microbeam. High resolution X-ray spectroscopy following micro-PIXE (Particle Induced X-ray Emission with micrometer-sized beams) with a focused (16)O ion beam was used. Focusing was performed with a heavy-ion scanning high-precision magnetic quadrupole triplet microprobe. Squamous Cell Carcinomas were induced on the right Cheek Pouch of Syrian Hamsters (HCP), sampled, cryo-sectioned and freeze-dried. Two-dimensional maps of elemental concentration were obtained by scanning the beam over the samples. Very non-uniform Cu concentrations were found in all sections.
Assuntos
Terapia por Captura de Nêutron de Boro/métodos , Metaloporfirinas/farmacocinética , Metaloporfirinas/uso terapêutico , Animais , Terapia por Captura de Nêutron de Boro/instrumentação , Carcinoma de Células Escamosas/metabolismo , Carcinoma de Células Escamosas/radioterapia , Bochecha , Cricetinae , Mesocricetus , Neoplasias Bucais/metabolismo , Neoplasias Bucais/radioterapia , Espectrometria por Raios X , Distribuição TecidualRESUMO
Human blood was irradiated with accelerated ions: 20 MeV 4He, 425 MeV 12C and 1480 MeV and 996 MeV 16O. For each ion, the blood was exposed to a range of doses as thin specimens in the track segment mode, so that irradiations took place at nearly constant LETs of 31.4, 61, 52 and 69 keV microm(-1), respectively. Lymphocytes were cultured to the first in vitro metaphase, analysed for chromosomal damage and the dicentric aberration frequencies fitted to the linear quadratic model of dose-response. For these high LET radiations, the linear (alpha) yield coefficient predominated and increased with LET, at least up to 60 keV microm(-1). Apart from the 996 MeV oxygen ions, the data indicated the presence of a quadratic (beta) coefficient, statistically consistent with values obtained with low LET radiations. However, the associated uncertainties on the measured beta values were large, illustrating the general problem that beta is more difficult to measure against a dominating and ever-increasing alpha term. The existence or otherwise of a beta component of the dose-response at these radiation qualities has important consequences for modelling mechanisms of aberration induction by radiation.
Assuntos
Aberrações Cromossômicas , Linfócitos/efeitos da radiação , Oxigênio , Prótons , Relação Dose-Resposta à Radiação , Íons Pesados , Humanos , Transferência Linear de Energia , Linfócitos/sangue , Metáfase , Aceleradores de Partículas , Eficiência Biológica RelativaRESUMO
A prospective study was undertaken to assess the radiotoxicity of accelerated particles in pulmonary alveolar macrophages (AM). We evaluated the effects of a single dose (10-75 Gy) of an external low-energy (20 MeV) proton beam on cultured AM oxidative metabolism and phagocytic function. Macrophages are the first line of defense against invading pathogens and are known to generate superoxide anion (O2), nitric oxide (NO), and mediators of antimicrobial and antitumoral defense mechanisms. We obtained AM by bronchoalveolar lavage from young (1-2 month old) and aged (9-12 month old) male Wistar rats. Cell viability, phagocytosis, O2 and NO production in control and proton-irradiated cultured AM were evaluated The effect of proton irradiation on cell viability was dose-dependent The higher doses induced a dramatic decrease in viability in the aged population. Phagocytosis increased 1.3-1.4 fold inboth populations irrespective of the dose delivered. Generation of O2 was always higher in the aged population for all the doses assayed and showed no significant variation from the control values. In the young population a clear increase was observed with doses of 25 and 50 Gy. NO production in AM from young animals rose in a dose-dependent manner. Conversely, proton irradiation did not affect NO production in macrophages from aged animals. The results of this study demonstrate that AM isolated from young and aged rats are functionally different and show a distinct behavior when exposed to proton irradiation. These findings suggest that age may condition response and must be taken into account when accelerated particle-radiotherapy protocols are considered as a valid therapeutic option for the treatment of cancer. To the best of our knowledge, this is the first report comparing sham-irradiated and proton-irradiated young and aged AM.
Assuntos
Envelhecimento/fisiologia , Macrófagos Alveolares/efeitos da radiação , Prótons , Animais , Sobrevivência Celular/efeitos da radiação , Células Cultivadas , Óxido Nítrico/metabolismo , Fagocitose/efeitos da radiação , Ratos , Ratos Wistar , Superóxidos/metabolismoRESUMO
Long-term exposure of aquatic organisms to metals, even those considered micronutrients, may affect their metabolism and produce sublethal effects. We evaluated the effects of long-term exposure of adult amphibian (Bufo arenarum) females to 4 microg/L of Zn(2+) (ZnSO(4) x H(2)O) in Ringer solution on the concentration of Zn and Fe, the activity of the key enzyme of the pentose phosphate pathway glucose 6-phosphate dehydrogenase, and glutathione content, both in the liver and ovary of these animals. We also performed early embryonic development studies by in vitro insemination from control and treated females. Zn exposure rendered lower Zn concentrations in the ovaries than did exposure of animals to Ringer solution without metal addition (97 +/- 50 versus 149 +/- 46 Zn microg/wet tissue g). Zn and Fe concentration correlation was positive and linear in the ovary, but was negative and nonlinear in the liver of the studied females. The activity of the enzyme glucose 6-phosphate dehydrogenase decreased (0.0599 +/- 0.0109 versus 0.0776 +/- 0.0263 micromol of NADPH/min x mg of proteins) and the endogenous glutathione content increased (0.027 +/- 0.005 versus 0.018 +/- 0.007 mg/10 mg of proteins) in the ovary but remained unaltered in the liver as a consequence of Zn treatment. Our results suggest the existence of different mechanisms of regulation of Zn and Fe concentrations in the ovary and in the liver of adult B. arenarum females. Binding of Zn to low-molecular-weight proteins, as metallothioneins, may occur in the liver, thus protecting this organ from toxic effects. In the ovary high-molecular-weight proteins, like glucose-6-phosphate dehydrogenase, should be able to bind Zn, leading to oxidative stress responsible for the observed increase in endogenous glutathione content. Inhibition of the pentose phosphate pathway in the ovary by Zn can be responsible for the reproductive failure that we detected through embryos survival studies during early life stages: 81.3 +/- 6.3% of embryos from control females survived versus 63.1 +/- 13.8% of embryos from Zn-treated females at the branchial circulation stage of development.
Assuntos
Bufo arenarum/fisiologia , Embrião não Mamífero/efeitos dos fármacos , Ovário/fisiologia , Poluentes Químicos da Água/efeitos adversos , Zinco/efeitos adversos , Animais , Bufo arenarum/embriologia , Desenvolvimento Embrionário , Feminino , Glucose-6-Fosfatase/efeitos dos fármacos , Glucose-6-Fosfatase/metabolismo , Fígado/efeitos dos fármacos , Fígado/fisiologia , Ovário/química , Ovário/efeitos dos fármacos , Estresse Oxidativo , Análise de Sobrevida , Distribuição Tecidual , Poluentes Químicos da Água/farmacocinética , Zinco/farmacocinéticaRESUMO
PURPOSE: Only leprosy resource centres undertake surgery for neuritis. Patients' accessibility to this surgical procedure is poor because these centres are often far from their homes. The aim of our work is to study the feasibility of neuritis surgery in the field. METHODS: A surgeon trained in this surgery was recruited by Bom-Pastor hospital in Brazilian Amazonia, which is located 400 km away from the leprosy resource centre. Patients operated from May 1996 to December 1997 were enrolled in this retrospective study. RESULTS: A total of 45 operations were carried out during 17 procedures on 13 patients, among which 12 were multibacillary cases. The decompression surgery was performed with a median delay of 1 year after leprosy diagnosis and 3.5 months after the neuritis diagnosis. Among 17 operations, 14 were performed for painful neuritis of recent onset unsuccessfully treated with corticoids or recurring during the month after corticoids were withdrawn. The other three operations were performed for long-standing neuritis with paralysis and deformity. Pain was relieved in all the cases of recent neuritis, except for one patient who suffered from a serious steroid-dependant erythema nodosum leprosum. An improvement of motor function was observed in one out of three patients with long-standing neuritis. Adverse effects were few: a scar infection with a rapid recovery and a keloid scar. Two neurites recurred 2 and 10 months after the surgery. CONCLUSIONS: In an endemic leprosy region, field access to surgery for neuritis appears to prove real progress in the management of leprosy neuritis.