Determination of the biodegradability of chitosan utilizing the most probable number technique

The present work aimed to evaluate the degradability of the chitosan polymer by soil microorganisms.This evaluation was accomplished using the Most Probable Number (MPN) method by plating in drops so that soil microorganisms capable of degrading the polymeric material could be quantified. Soil samples diluted in three specific culture media for each typeof microorganism were plated –bacteria, fungi and actinobacteria–and they were maintained at 28°C for seven days to determine the growth rate of fungi and actinobacteria, and for 48hoursfor the development of bacteria. Significant differences in the MPN of actinobacteriarelative to the other groups analyzed were observed. Thus, the method used was effective for determining the degradability of the chitosan biopolymer when observing the development of microorganisms subjected to the replacement of thecarbonsource by the addition of 2% w v-1of the chitosan biopolymer to the culture medium. The formation of clear regions around the microbial colonies was a strong indicator of biodegradation.

Estudo comparativo para avaliação das falhas técnicas em radiografias convencionais de tórax / Comparative study to determine technical failures affecting conventional chest radiography

OBJECTIVE: To specify and quantify main technical failures, whether mechanical or electronic, encountered at conventional chest radiography, in order to improve imaging quality, thus reducing the necessity of additional images acquisition and, consequently, the radiation dose received by the patients. MATERIALS AND METHODS: A pulmonologist selected and reviewed 897 conventional chest radiographic films in either posteroanterior or lateral views, performed in five health institutions in the city of São Paulo. The films were individually analyzed in the search of technical failures, and classified according predefined technical radiographic errors which had led to re-examination. RESULTS: The obtained results have demonstrated that incorrect patient positioning (27%), underexposure (23%) and overexposure (15%) were the main failures contributing to repetition of examinations, with a Pearson correlation coefficient > 0.7%, thus leading to an increase in the dose received by the patients. CONCLUSION: The results of the present study indicate the need for X-ray apparatuses quality control, improvement of operators' skills, as well as further studies to clarify the impact resulting from examinations repetition.

OBJETIVO: Especificar e quantificar as principais falhas técnicas, sejam elas eletrônicas ou mecânicas, presentes em radiografias convencionais de tórax, com o intuito de melhorar a sua qualidade e reduzir a necessidade da repetição dos exames e, consequentemente, a dose recebida pelo paciente. MATERIAIS E MÉTODOS: Foram selecionadas e avaliadas por um pneumologista 897 radiografias convencionais realizadas ou em projeção posteroanterior ou lateral em cinco instituições de saúde da cidade de São Paulo. Em cada uma delas foram feitas análises das falhas técnicas presentes, as quais foram classificadas de acordo com o erro técnico radiográfico pré-definido e que levou à repetição do exame. RESULTADOS: Os resultados obtidos mostraram que o posicionamento incorreto do paciente (27%), a subexposição (23%) e a superexposição (15%) foram as principais falhas que contribuíram para a repetição dos exames e que apresentaram, na matriz de coeficiente de correlação Pearson, um erro acima de 0,7%, ocasionando aumento da dose recebida pelos pacientes. CONCLUSÃO: Os resultados observados indicaram a necessidade da realização de controle de qualidade dos aparelhos de raios X, a atenção do operador do equipamento, bem como outras abordagens para esclarecer o impacto da necessidade de repetição do exame.