Artigo de peri??dico
Conversion Coefficients of equivalent and effective doses in terms of air kerma for computational scenarios of Total Body Irradiation in lying-down patients
Registro en:
0969-806X
159
10.1016/j.radphyschem.2019.02.051
60.153
73.00
Autor
CUNHA, J.S.
SANTOS, W.S.
CARVALHO JUNIOR, A.B.
Resumen
This study aimed to calculate the Conversion Coefficients (CC) of Equivalent and Effective doses by air kerma
considering Total Body Irradiation scenarios with Varian linear accelerator with photon beams energy of 4, 6,
10, 15, 18, and 25 MV. The simulations were performed in the MCNPX code and the University of Florida (UF)
phantoms were used to represent exposed lying down adult patients in the AP, PA, RLAT, and LLAT irradiation
geometries. Lead attenuators were inserted in the scenarios for the preservation of organs of risk and their
contribution were analyzed for CC. For most counts, the statistical uncertainty was approximately 5%. For the
gonads, CC values for the male phantom decreased with the increase of energy in the AP geometry, which did not
occur for the female phantom. As the beam becomes more penetrating, the ovary absorbs more energy because
of its internal position. Considering the lung, an organ of risk in TBI, the insertion of the attenuators in the
scenarios caused the CC values to reduce by more than 30%. For organs and tissues such as skin and male
breasts, the attenuators caused the dose to increase. As for the active bone marrow, which is the TBI target tissue,
it was not possible to obtain a good estimate for CC at 15, 18, and 25 MV due to a limitation of the method used
to calculate the dose in the bone areas. Nevertheless, for lower energies the CC values for the marrow were valid.