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 Fifty minutes later, the spleens and livers were withdrawn and prepared to be studied.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 Fifty minutes later, the spleens and livers were withdrawn and prepared to be studied.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.

Application of a new source model of a panoramic gamma irradiator on dose map formation in an irradiated product.

The computer simulation of radiation processing in an industrial panoramic gamma facility generates a number of complex scientific and technical problems; for example, the product is manually loaded onto turntables and rotates during the entire irradiation and the Monte Carlo MCNP three-dimensional geometry simulation is static. This causes the first problem; for this it is necessary to introduce additional approaches to describe the real irradiation process. It is important to properly represent the irradiation process and the specific conditions of the irradiator to correctly reproduce the measured results and guarantee also through the use of the model developed the most accurate dose map formations in an irradiated product, improving the service quality provided to the customer. The objective of this study is to apply the proposed source model of a panoramic gamma irradiator on dose distributions in containers of different geometric shape of an irradiated product with use of the Monte Carlo code. The influence was studied with use of a new homogenized annular source model. The validation of the MCNPX model of the GammaBeam 127 source was performed by measurements. The validation of the proposed model was based on comparative evaluation of the MCNPX absorbed-dose rates (Gy/h) in the irradiated product between the real source model and the new model. The comparative results for the MCNPX absorbed-dose rate showed that the new source model provides a better description of the irradiation process in a panoramic gamma irradiator. This indicates that the physical and mathematical MCNPX models developed are reliable and correct, and the new source model adequately reproduces the observed dose distributions in the different geometric shapes of the irradiated product.

New source models to represent the irradiation process in panoramic gamma irradiator.

The use of gamma irradiation technologies generates a number of complex scientific and technical problems; for example, the target is manually loaded onto turntables and is rotated during the entire irradiation process and the MCNPX three-dimensional geometry simulation is kept static. For this, it is necessary to introduce additional approaches. In this paper, two new methodologies are proposed for the simulation of irradiation process in panoramic gamma irradiator. The study was performed at the gamma irradiation facility at the Nuclear Technology Development Center of the National Nuclear Energy Commission, Brazil. The source can be reproduced with a homogenized geometry. Validation of MCNPX calculations of gamma doses were performed by thorough comparison with the experimental measurements. The contribution of this proposed source models has opened new lines of research. The results of this study showed that the proposed source models effectively represent the irradiation process.