Megavoltage radiotherapy effects on organs of the reticuloendothelial system.

PURPOSE: To study the uptake capacity of cells from the reticuloendothelial system after irradiation with high-energy X-rays. METHODS: Eighteen male Wistar rats were distributed in three groups: group A (n = 6): control, unirradiated animals studied alongside animals from group B; group B (n = 6) and group C (n = 6): animals irradiated and studied after 24 and 48 hours, respectively. The rats were anesthetized and placed on a 10 MV linear accelerator. Next, they were irradiated in the abdominal region, with 8 Gy. Twenty-four (groups A and B) and 48 hours later (group C), a colloidal carbon solution (1 mL/kg) was intravenously injected in the tail vein. Fifty minutes later, the spleens and livers were withdrawn and prepared to be studied. Kupffer cells and splenic macrophages containing carbon pigments were counted in an optical microscope. Arithmetic means were calculated for each group and compared among them. RESULTS: X-rays were associated with a reduced number of Kupffer cells containing colloidal carbon, proliferation and enlargement of biliary ducts, hypoplasia, and hepatocyte necrosis. In the irradiated spleen, the colloidal carbon uptake was concentrated in the marginal zone around the white pulp, with an inexpressive uptake of pigments by macrophages from white and red pulps. CONCLUSIONS: The X-rays in the rat abdomen are associated with a reduction in the Kupffer cells uptake of colloidal carbon, hepatocyte disorders, bile duct proliferation, and splenic uptake of colloidal carbon concentrated in the marginal zone.

Megavoltage radiotherapy effects on organs of the reticuloendothelial system

Purpose: To study the uptake capacity of cells from the reticuloendothelial system after irradiation with high-energy X-rays. Methods: Eighteen male Wistar rats were distributed in three groups: group A (n = 6): control, unirradiated animals studied alongside animals from group B; group B (n = 6) and group C (n = 6): animals irradiated and studied after 24 and 48 hours, respectively. The rats were anesthetized and placed on a 10 MV linear accelerator. Next, they were irradiated in the abdominal region, with 8 Gy. Twenty-four (groups A and B) and 48 hours later (group C), a colloidal carbon solution (1 mL/kg) was intravenously injected in the tail vein. Fifty minutes later, the spleens and livers were withdrawn and prepared to be studied. Kupffer cells and splenic macrophages containing carbon pigments were counted in an optical microscope. Arithmetic means were calculated for each group and compared among them. Results: X-rays were associated with a reduced number of Kupffer cells containing colloidal carbon, proliferation and enlargement of biliary ducts, hypoplasia, and hepatocyte necrosis. In the irradiated spleen, the colloidal carbon uptake was concentrated in the marginal zone around the white pulp, with an inexpressive uptake of pigments by macrophages from white and red pulps. Conclusions: The X-rays in the rat abdomen are associated with a reduction in the Kupffer cells uptake of colloidal carbon, hepatocyte disorders, bile duct proliferation, and splenic uptake of colloidal carbon concentrated in the marginal zone.

Radiation oncology in vitro: trends to improve radiotherapy through molecular targets.

Much has been investigated to improve the beneficial effects of radiotherapy especially in that case where radioresistant behavior is observed. Beyond simple identification of resistant phenotype the discovery and development of specific molecular targets have demonstrated therapeutic potential in cancer treatment including radiotherapy. Alterations on transduction signaling pathway related with MAPK cascade are the main axis in cancer cellular proliferation even as cell migration and invasiveness in irradiated tumor cell lines; then, for that reason, more studies are in course focusing on, among others, DNA damage enhancement, apoptosis stimulation, and growth factors receptor blockages, showing promising in vitro results highlighting molecular targets associated with ionizing radiation as a new radiotherapy strategy to improve clinical outcome. In this review we discuss some of the main molecular targets related with tumor cell proliferation and migration as well as their potential contributions to radiation oncology improvements.

Avaliaçäo do volume pulmonar irradiado no tratamento conservador do câncer de mama / A method of estimating the irradiated lung volume in primary breast irradiation

Resumo: A irradiaçäo dos campos tangentes mamários inclui certa quantidade do volume pulmonar, o que pode levar a uma pneumonite radiógena. O volume de pulmäo irradiado pode ser avaliado medindo-se a altura do parênquima pulmonar irradiado (API) pelas radiografias de posicionamento ("portals"). Considera-se tecnicamente satisfeitos sempre que a API for menor ou igual a 2,5cm. Analisamos retrospectivamente "portals" de 100 pacientes, tratadas entre janeiro de 1996 e junho de 1997. Tomamos o contornodas mamas das pacientes e, por intermédio da geometria do feixe de radiaçäo, observamos o ângulo para incidência dos campos tangentes . Em 71 por cento dos casos este ângulo conduziu a uma API maior do que 2,5cm o que necessitou novo arranjo dos campos. Realizamos análise estatística objetivando encontrar uma expressäo matemática que relacionasse a API com os parâmetros geométricos do tratamento. O ajuste linear obtido, embora útil, näo foi inteiramente satisfatório, provavelmente devido a variaçöes anatômicas individuais ou a exclusäo de variáveis.

Automação do cálculo da dose de campos irregulares em radioterapia / Automation of irregular fields dose calculations in radiotherapy

Utilizando a aproximação de Clarkson, desenvolvemos um método computacional para obter a dose em campos irregulares. Diferentemente de outros métodos apresentados, levamos em conta a dependência não-linear da razão espalhamento-ar (SAR) com a profundidade e tamanho de campo. Ajustando equações de um modelo teórico aos dados tabelados de SAR para campos circulares, obtêm-se os parâmetros numéricos dessas equações, com os quais o SAR é obtido para um dado tamanho de campo e profundidade. Com este método nenhuma interpolação é necessária e os erros nos valores de dose são exclusivamente de natureza experimental na determinação dos valores dos SARs. As dependências funcionais do SAR foram introduzidas em um programa de microcomputador para cálculo da dose. Comparamos valores de dose obtidos pelo método proposto com aqueles obtidos pelo cálculo manual e encontramos erros menores que 1,5 por cento em pequenas profundidades e erros da ordem de até 10 por cento para grandes profundidades. Os erros encontrados são atribuídos ao grande número de interpolações lineares que são executadas e à não-linearidade das curvas de SAR.