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Atomic, Argentina

Hopewell J.W.,University of Oxford | Morris G.M.,Brookhaven National Laboratory | Schwint A.,Constituyentes Atomic Center | Coderre J.A.,ORA Inc
Applied Radiation and Isotopes

The radiobiology of the dose components in a BNCT exposure is examined. The effect of exposure time in determining the biological effectiveness of γ-rays, due to the repair of sublethal damage, has been largely overlooked in the application of BNCT. Recoil protons from fast neutrons vary in their relative biological effectiveness (RBE) as a function of energy and tissue endpoint. Thus the energy spectrum of a beam will influence the RBE of this dose component. Protons from the neutron capture reaction in nitrogen have not been studied but in practice protons from nitrogen capture have been combined with the recoil proton contribution into a total proton dose. The relative biological effectiveness of the products of the neutron capture reaction in boron is derived from two factors, the RBE of the short range particles and the bio-distribution of boron, referred to collectively as the compound biological effectiveness factor. Caution is needed in the application of these factors for different normal tissues and tumors. © 2011 Elsevier Ltd. Source

Boggio E.F.,Bariloche Atomic Center | Longhino J.,Bariloche Atomic Center | Provenzano L.,CONICET | Farias R.,CONICET | And 5 more authors.
IFMBE Proceedings

BNCT is a cancerous cells selective, nonconventional radiotherapy modality to treat malignant tumors such as glioblastoma, melanoma and recurrent head and neck cancer. It consists of a two-step procedure: first, the patient is injected with a tumor localizing drug containing a nonradioactive isotope (Boron-10) with high slow neutron capture cross-section. Secondly, the patient is irradiated with neutrons, which are absorbed by the Boron-10 agent with the subsequently nuclear reaction B-10(n,a)Li-7, thereby resulting in dose at cellular level due to the high-LET particles. The Argentine clinical facility for superficial tumors treatment is located at the RA-6 Research Reactor (Bariloche Atomic Center). Due to the beam penetration, the total absorbed dose in the first few millimeters of tissue is lower than in the maximum flux. Thus, the introduction of a suitable device over the irradiated area is considered to allow a local dose increase by means of high energy Beta particles emission, without substantially perturbing the primary in-depth dose profile. These devices are called Beta Enhancers (BE) and were studied by Monte Carlo transport code modeling, experimental measurements and retrospective treatment planning evaluation of selected nodular melanoma treatments of the Argentine BNCT patients. Pre-clinical studies were carried out in a nude mice cancer model for BNCT at the RA-6 facility, in order to preliminarily assess toxicity and efficacy of BE in-vivo implementation. Nude mice were separated into five groups of 5-9 animals each: control group, NCT (without boron agent) irradiation, NCT+BE irradiation, BNCT irradiation and BNCT+BE irradiation. The results demonstrate the technique efficacy, highlighted between NCT and NCT+BE groups. There was no toxicity evidence. © Springer International Publishing Switzerland 2015. Source

Aromando R.F.,University of Buenos Aires | Aromando R.F.,Constituyentes Atomic Center | Trivillin V.A.,Constituyentes Atomic Center | Heber E.M.,Constituyentes Atomic Center | And 5 more authors.
Oral Oncology

Mast cell (MC) activation in the hamster cheek pouch cancerization model is associated with the increase in tumor cell proliferation, mediated in turn by tryptase, a protease released from mast cell granules after activation. Tryptase induces tumor cell proliferation through the activation of PAR-2 (protease activated receptor-2) on the plasma membrane of carcinoma cells. The therapeutic success of boron neutron capture therapy mediated by boronophenylalanine (BPA-BNCT) in tumor control in the hamster cheek pouch oral cancer model has been previously reported by our laboratory. Early effects of BPA-BNCT on tumors of the hamster cheek pouch include a reduction in DNA-synthesis with the concomitant decrease in the proliferation of malignant cells. The aim of the present study was to investigate the early histological changes in mast cells after BPA-BNCT in tumors and premalignant tissue of the hamster cheek pouch. Tumor-bearing pouches were treated with BPA-BNCT or beam only (neutron irradiation without prior administration of the boron compound) and sacrificed 1 day after treatment. The samples were fixed in Carnoy fixative and stained with alcian blue-safranin to identify all the populations of mast cells. Total, active and inactive mast cells (MC) were counted in the connective tissue and the adventitious tissue underlying the pouch wall and at the base of the tumors in pouches treated with BPA-BNCT, in keeping with a previously described technique. BPA-BNCT induced a marked reduction in the total number of mast cells in the pouch (p < 0.05). This reduction in the total number of mast cells was due to a reduction in mast cells at the base of the tumor (p < 0.005) and it occurred at the expense of the active mast cells (p < 0.05). A slight reduction that did not reach statistical significance also occurred in the amount of mast cells in the pouch wall (that corresponds to the premalignant tissue in tumor-bearing pouches), and in the adventitious tissue. In this case the reduction was seen in the inactive population. Both BPA-BNCT and beam only elicited a qualitative change in the secretion modality of the granule content. Although further studies are needed to evaluate the subcellular effect of BNCT on mast cell granule secretion, the reduction in cell proliferation induced by BPA-BNCT would be partially due to the decrease in total mast cells in the hamster check pouch. © 2010 Elsevier Ltd. All rights reserved. Source

Fava J.,Constituyentes Atomic Center | Fava J.,National University of Costa Rica | Muller S.,Constituyentes Atomic Center | Lanzani L.,Constituyentes Atomic Center | And 3 more authors.
Studies in Applied Electromagnetics and Mechanics

The electrical conductivities of ad-hoc specimens of Zircaloy-4 (Zry-4) with hydrogen contents between 5.9 and 2019 wt ppm were measured by eddy current (EC) and by van der Pauw's method. The EC evaluation was made by a non-conventional, non-comparative procedure, which gives the conductivity values through fittings of the theoretical and measured probe impedances for each specimen. Specially designed planar bobbin coil was used. The electromagnetic EC problem was solved in the test conditions. The EC conductivity measurements were made on both major faces of the specimens, i.e. the one with the oxide layer and the ground-off oxide-free face. The van der Pauw's measurements were made on the oxide-free face only. The measured electrical conductivities can be grouped in three bands corresponding to low, medium and high hydrogen contents. In all cases, the total range of conductivity variation for the studied specimens was about 2.5% of the largest value. The conductivity resolution of the procedure was about 0.8%. © 2014 The authors and IOS Press. Source

Molinari A.J.,Constituyentes Atomic Center | Pozzi E.C.C.,Constituyentes Atomic Center | Pozzi E.C.C.,Research and Production Reactors | Hughes A.M.,Constituyentes Atomic Center | And 13 more authors.
Radiation Research

In the present study the therapeutic effect and potential toxicity of the novel "“Sequential"†boron neutron capture therapy (Seq-BNCT) for the treatment of oral cancer was evaluated in the hamster cheek pouch model at the RA-3 Nuclear Reactor. Two groups of animals were treated with "Sequential"BNCT, i.e., BNCT mediated by boronophenylalanine (BPA) followed by BNCT mediated by sodium decahydrodecaborate (GB-10) either 24 h (Seq-24h-BNCT) or 48 h (Seq-48h-BNCT) later. In an additional group of animals, BPA and GB-10 were administered concomitantly [(BPA + GB-10)-BNCT]. The single-application BNCT was to the same total physical tumor dose as the "Sequential"BNCT treatments. At 28 days post-treatment, Seq-24h-BNCT and Seq-48h-BNCT induced, respectively, overall tumor responses of 95 ±2% and 91 ±3%, with no statistically significant differences between protocols. Overall response for the single treatment with (BPA + GB-10)-BNCT was 75 ±5%, significantly lower than for Seq-BNCT. Both Seq-BNCT protocols and (BPA + GB-10)-BNCT induced reversible mucositis in the dose-limiting precancerous tissue around treated tumors, reaching Grade 3/4 mucositis in 47 ±12% and 60 ±22% of the animals, respectively. No normal tissue toxicity was associated with tumor response for any of the protocols. "Sequential"BNCT enhanced tumor response without an increase in mucositis in dose-limiting precancerous tissue. © 2011 by Radiation Research Society. All rights of reproduction in any form reserved. Source

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