Artigo de peri??dico
Estimate of S-values for children due to six positron emitting radionuclides used in PET examinations
Registro en:
0969-806X
140
10.1016/j.radphyschem.2017.02.038
43.267
Autor
BELINATO, WALMIR
SANTOS, WILLIAM S.
PERINI, ANA P.
NEVES, LUCIO P.
CALDAS, LINDA V.E.
SOUZA, DIVANIZIA N.
Resumen
Positron emission tomography (PET) has revolutionized the diagnosis of cancer since its conception. When
combined with computed tomography (CT), PET/CT performed in children produces highly accurate diagnoses
from images of regions affected by malignant tumors. Considering the high risk to children when exposed to
ionizing radiation, a dosimetric study for PET/CT procedures is necessary. Specific absorbed fractions (SAF)
were determined for monoenergetic photons and positrons, as well as the S-values for six positron emitting
radionuclides (11C, 13N, 18F, 68Ga, 82Rb, 15O), and 22 source organs. The study was performed for six pediatric
anthropomorphic hybrid models, including the newborn and 1 year hermaphrodite, 5 and 10-year-old male and
female, using the Monte Carlo N-Particle eXtended code (MCNPX, version 2.7.0). The results of the SAF in
source organs and S-values for all organs showed to be inversely related to the age of the phantoms, which
includes the variation of body weight. The results also showed that radionuclides with higher energy peak
emission produces larger auto absorbed S-values due to local dose deposition by positron decay. The S-values
for the source organs are considerably larger due to the interaction of tissue with non-penetrating particles
(electrons and positrons) and present a linear relationship with the phantom body masses. The results of the Svalues
determined for positron-emitting radionuclides can be used to assess the radiation dose delivered to
pediatric patients subjected to PET examination in clinical settings. The novelty of this work is associated with
the determination of auto absorbed S-values, in six new pediatric virtual anthropomorphic phantoms, for six
emitting positrons, commonly employed in PET exams.