Computational study of internal dosimetry in images and therapy with radiopharmaceuticals

The individual calculation of internal dosimetry with radiopharmaceuticals becomes very difficult due to the structures and metabolism complexity of the human body. Monte Carlo simulations can make it more realistic. Among the experimental methods of dose determination are thermoluminescent dosemeters (TLD), which measure the dose either in a point or in a plane. One way to obtain the dose in a object with complex geometry is with TLDs distribution around the studied volume or using MAGIC-f polymeric gel. The objective of this work is to evaluate the dose deposition in objects filled with MAGIC-f polymeric gel through Monte Carlo simulation with GATE application. Two geometries were modeled: cylindrical test tubes (diameter 1.5 cm and height 7 cm) and cubes (edge 0.5 cm) placed at increasing distances of a point source of ^99mTc with activity of 1 mCi, during 1 s of exposure. The analytical dose calculation for comparison with the cubes simulation was performed. The cylinders and cubes were positioned at 4, 6, 8, 10, 12, 14, 16 and 18 cm from the source. The dose values for both cylinders and cubes showed a dose reduction behavior with the square distance and have dose values compatible with the difference between the cylinders and cubes volumes. It is concluded that the Monte Carlo simulations with GATE application are consistent with analytical dose calculations for different distances and present values compatible with the different simulated targets volumes. It is intended, in the future, to evaluate experimentally the simulated arrangements using MAGIC-f polymer gel and TLD dosimeters, in order to validate the results. (author)