RESUMO
The effects of pH (3.5, 4.5, and 5.5) and UV-C irradiation dose (12.8, 24.2, 35.8, and 54.6â¯mJ/cm2) on the physicochemical properties changes in 10% Aloe vera gel blends; in addition, the acemannan concentration and structural changes in the precipitated polysaccharides were evaluated. A thermal treatment (TT; 45â¯s at 90⯰C) was used for comparison. In contrast to TT, a dose of 24.2â¯mJ/cm2 did not induce significant changes of free sugar content. Moreover, TT and UV-C irradiation did not significantly affect the content of mannose but increased those of galactose, fructose, and glucose. 1H NMR analysis revealed minimal changes in the isolated fractions of acemannan, indicating that compared to the unprocessed control sample, the acemannan deacetylation was more pronounced by TT (27%) than by UV-C irradiation (11% at 54.6â¯mJ/cm2), without any significant difference between the two. UV-C irradiation of Aloe vera gel blends at pH 3.5 and 24.2â¯mJ/cm2 was an alternative to TT and efficiently preserve the characteristics of acemannan.
Assuntos
Aloe/química , Géis/química , Mananas/química , Preparações de Plantas/química , Géis/efeitos da radiação , Calefação , Hexoses/química , Concentração de Íons de Hidrogênio , Mananas/efeitos da radiação , Peso Molecular , Preparações de Plantas/efeitos da radiação , Sacarose/química , Raios UltravioletaRESUMO
Gel dosimetry has been studied mainly for medical applications. The radiation induced ferric ions concentration can be measured by different techniques to be related with the absorbed dose. Aiming to assess gamma/thermal neutrons dose from research reactors, Fricke gel and alanine gel solutions produced at IPEN using 300 bloom gelatin were mixed with Na(2)B(4)O(7) salt, and the mixtures were irradiated at the beam hole #3 of the IEA-R1 research reactor, (BH#3) adapted to BNCT studies, and the dose-response was evaluated using spectrophotometry technique.
Assuntos
Alanina/efeitos da radiação , Terapia por Captura de Nêutron de Boro/instrumentação , Compostos Ferrosos/efeitos da radiação , Soluções/efeitos da radiação , Dosimetria Termoluminescente/instrumentação , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Raios gama , Géis/efeitos da radiação , Nêutrons , Doses de Radiação , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
This work presents Vibro-acoustography (VA) as a tool to visualize absorbed dose distributions in a polymer gel dosimeter. VA uses the radiation force of focused ultrasound to vibrate a small region of the sample. Different modalities of VA were used to investigate the feasibility of this technique to evaluate dose distribution in irradiated 'MAGIC' polymer gel. A phantom was designed using this polymer with 2% w/w added glass microspheres having an average diameter range between 40-75 microm. The phantom was irradiated using conventional 10 MeV X-rays from a linear accelerator at a distance of 100 cm. An absorbed dose of 50 gray was delivered to the gel. To study the phenomena of dose distribution, continuous wave (CW), toneburst and multifrequency VA were applied to the phantom. Images were generated from the phase and magnitude of the emitted sound from the irradiated area. The comparative accuracy of the different VA results were validated using transverse relaxation rate (R2) image analysis by Magnetic Resonance Imaging (MRI) and a treatment planning system. A contour map of R2 was registered with the transverse CW images, obtained with the focal point on the top surface, and a good correlation was found between the images. The axial profile of irradiated inclusion from the toneburst VA image obtained with excitation frequency of 75 kHz showed the best accuracy compared to other VA modalities. The results show that VA imaging has potential to visualize dose distribution in a polymer gel dosimeter.
Assuntos
Técnicas de Imagem por Elasticidade/instrumentação , Géis/química , Géis/efeitos da radiação , Radiometria/instrumentação , Técnicas de Imagem por Elasticidade/métodos , Desenho de Equipamento , Análise de Falha de Equipamento , Imagens de Fantasmas , Doses de Radiação , Radiometria/métodos , Reprodutibilidade dos Testes , Espalhamento de Radiação , Sensibilidade e EspecificidadeRESUMO
The spatial accuracy of magnetic resonance imaging (MRI) Fricke-gel dosimetry is limited by diffusion of ferric ions. This paper describes a honeycomb structure to limit diffusion of Fe3+ ions in a three-dimensional phantom. Such a phantom containing the dosimeter gel was irradiated to a known dose distribution. Maps of dose distributions were produced from the MR images acquired at 2 and 24 hours after the dose was given. The dose distribution maps verified that the honeycomb structure precludes ion diffusion from one honeycomb cell to another, thus improving the usefulness of MRI Fricke-gel dosimetry.
Assuntos
Compostos Ferrosos/efeitos da radiação , Géis/efeitos da radiação , Imageamento por Ressonância Magnética/instrumentação , Radiometria/instrumentação , Soluções/efeitos da radiação , Radioisótopos de Cobalto , Relação Dose-Resposta à Radiação , Desenho de Equipamento , Aumento da Imagem/instrumentação , Aumento da Imagem/métodos , Imageamento por Ressonância Magnética/métodos , Imagens de Fantasmas , Controle de Qualidade , Radiometria/métodos , Planejamento da Radioterapia Assistida por Computador/instrumentação , Planejamento da Radioterapia Assistida por Computador/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Sefarose/efeitos da radiaçãoRESUMO
The interaction of plasma proteins such as albumin, gamma-globulin, and fibrinogen with the surface of graft copolymers DMAA-G-PTFE, DMAA-G-PETFE, and DMAA-G-PE obtained by radiation graft polymerization was studied. The adsorption of serum proteins was affected by the hydrophilicity of the graft copolymers. Increased albumin adsorption and decreased fibrinogen and gamma-globulin adsorption with increasing grafting levels was shown. A certain range of degrees of grafting showed an improved blood compatibility of the polymeric surfaces due to the existence of a hydrophilic/hydrophobic balance on the polymers. The results suggest that the DMAA-G-PTFE, DMAA-G-PETFE, and DMAA-G-PE graft copolymers can be used as biomaterials for long-term use in cardiovascular systems.