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High-resolution 3D dose distribution measured for two low-energy x-ray brachytherapy seeds: I125 and PD103



Guerda Massillon, Ronaldo Minniti, Michael G. Mitch, Christopher G. Soares


An investigation of the three-dimensional (3D) absorbed dose distribution around two low-energy photon (125I and 103Pd) brachytherapy seeds is presented. A high spatial resolution 3D gel scanning system has been utilized. The radial dose function, g(r), as well as the absorbed dose rate in the plane (2D) parallel to the longitudinal axis of the sources has been obtained at various radial distances. At large distances from the source, the absorbed dose delivered is similar to that predicted from published Monte Carlo calculations for both seeds. However for distances close to the source the differences are quite significant for the 103Pd seed. The largest difference is observed for the absorbed dose delivered by the 103Pd seed. A large enhancement of the absorbed dose is observed in the radial dose function for distances below 4 mm. This difference between the calculations and the measurement is not only in magnitude but also in the shape of g(r). The shape of the absorbed dose function predicted by published Monte Carlo calculations assumes essentially that the emission outside the seed encapsulation is that of a pure photon emitter. However the observed enhancement suggests the contribution of other radionuclide in the seed with radiation emission types resembling that of a short range interaction such as high energy beta particles or electrons. The observations presented in this work at close distances from the source can only be revealed with a high-spatial resolution dosimetry system
Medical Physics


3D dose distribution, BANG gel dosimetry, brachytherapy seeds, high-resolution optical CT scanner, low-energy x-rays


Massillon, G. , Minniti, R. , Mitch, M. and Soares, C. (2010), High-resolution 3D dose distribution measured for two low-energy x-ray brachytherapy seeds: I125 and PD103, Medical Physics (Accessed June 22, 2024)


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Created November 3, 2010, Updated February 19, 2017