Page 210 - 00. Complete Version - Progress Report IPEN 2014-2016

210 Nuclear Science and Technology | Progress Report

saturation curve, ions collection efficiency, 5 years old head size. It can be seen at Fig.13.
polarity effect and the linearity of the ioniza- The results showed attenuation up to 23%
tion chamber response. For the implementa- when different materials are used as skullcap,
tion of the methodology, the radiation qualities demonstrating that the DRL’s adopted could
the T- 10 to T-100 were established, follow- be overestimating the dose received by pedi-
ing the recommendations of the IAEA code atric patients.
of practice, TRS 398. The reference ionization
chamber positioned in the PMMA phantom
is shown Fig. 12.

Figure 13. Head pediatric phantom: cortical
(aluminum) and cancellous (PVC) bone.

PRODUCTS AND SERVICES

Institutional Environmental
Figure 12. Parallel plate ionization chamber po-
sitioned in the PMMA phantom. Radiological Monitoring Program

The Environmental Radiometry Laboratory of
To improve the dosimetry in computed tomog- the Radiation Metrology Center is responsible
raphy procedures, a guide providing informa- for the planning and execution of the Institu-
tion to the adequate use of a calibrated pencil tional Environmental Radiological Monitoring
ionization chamber was developed. The guide Program (PMRA). This Program is developed in
includes guidance prior knowledge of half val- a two-fold approach.
ue layer (HVL), as it is necessary to know the
effective beam energy for application quality Preventive evaluation involves collection of
for correction factor (kq). In this work, it was effluent samples generated at IPEN, includ-
decided to test a Tandem System consisting of ing those from Radiopharmacy Program and
five aluminum and three PMMA cylindrical ab- Research Reactor Center, and the character-
sorbing layers coupled to the pencil ionization ization of their radioactive contents. Subse-
chamber. Using Tandem curves, it was possi- quently, the radiation effective doses of the
ble to assess HVL values and the calibration critical groups of population are assessed on
coefficients to the appropriate beam. an annual basis, by using dispersion models
recommended by IAEA.
To contribute to the Diagnostic Reference Lev-
els determination to pediatric CT scans, a head The confirmatory evaluation is performed by
pediatric phantom using materials to simulate collection and analysis of samples from envi-
the skullcap was developed: cortical bone (alu- ronmental matrices including atmospheric air,
minum) and cancellous bone (PVC). It was filled soil, groundwater and rainwater in IPEN’s sur-
with distilled water. Its dimension follows the roundings, in order to determine their radio-
recommendation of the World Health Orga- active contents. Several analytical techniques
nization and the UCRU for children from 0 to such as gamma-ray spectrometry, liquid scin-

Instituto de Pesquisas Energéticas e Nucleares