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Dosimetric characterization of Co-60 HDR brachytherapy sources is presented in this page. The results have been obtained using the simulation code PENELOPE (version 2011) following the reports AAPM TG-43 (and TG-43 U1) and the recommendations from AAPM and ESTRO report.
The dosimetric characterization in water have been calculated and includes the radial dose function, the anisotropy function, the air-kerma strength, the dose rate constant and the absorbed dose rate.
Disclaimer:The information in these pages support the results section of our papers and they should not be used in clinical practice without rigorous verification by the user.
The Monte Carlo simulation of the radiation transport was performed using the version 2011 of the code PENELOPE. This code satisfies the recommendations of the Task Group 43 of the AAPM. Among other characteristics, it contains a set of numerical data and analytical fits of the XCOM and EPDL97 libraries for the evaluation of the cross sections for the photoelectric effect.
Air Kerma Strength (Sk) have been calculated by determining the photon fluence rate assuming the source in vacuum and scoring the photons passing through a spherical surface with a radius of 1 m, centered on the active core of the source. The corresponding 2D histogram was defined with bins of widths ΔΘ = 1º and ΔE = 1 keV. These widths avoid the appearance of artifacts linked to the use of larger scoring voxels.
Absorbed dose rate in water have been calculated by situating the source inside a spherical water (ρ = 0.998 g/cm3) phantom of radius 1 m, with the origin of the coordinate system in the center of the cobalt core and the Z axis along the source pointing towards the forward end of the capsule. The energy deposited in the water phantom was scored and the dose rate per unit of Sk was obtained. Two different scoring voxel types were used. In the first one, a total of 800 × 1600 annular cylindrical voxels with Δz = 0.05 cm and Δρ = 0.05 cm, corresponding to 0 ≤ ρ ≤ 40 cm and −40 cm ≤ z ≤ 40 cm, were considered. The second one included 800 × 180 spherical voxels with Δr = 0.05 cm and Δθ = 1º. The 2D absorbed dose rate in water was obtained together with all parameters and functions of TG-43U1 formalism: the absorbed dose rate constant, the radial dose function and the 2D anisotropy function. The linear source approximation was assumed.
| Energy (keV) | Intensity (%) |
|---|---|
| 7.325 | 5.6 x 10−9 |
| 7.478 | 0.0067 |
| 7.461 | 0.00343 |
| 8.265 | 0.001223 |
| 8.329 | 7.4 x 10−7 |
| 8.333 | 6.8 x 10−11 |
| 346.930 | 0.0076 |
| 826.060 | 0.0076 |
| 1173.237 | 99.9736 |
| 1332.501 | 99.9856 |
| 2158.570 | 0.00111 |
| 2505.000 | 2.0 x 10−6 |
⇒ University of Valencia: http://www.uv.es/braphyqs
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