Page 67 - PR 2014 2016 07 Nuclear Science and Technology

Nuclear Science and Technology | Progress Report 209

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information in relation to the new proce- be calibrated, using gamma ( Co) or low en-
dures were integrated in one database. The ergy X radiation. As a reference system, a
improvements implemented have reduced secondary standard ionization chamber is
costs and increased productivity. used, traceable to the Physikalisch-Technische
Bundesanstalt, PTB, Germany, and to the Na-
Diagnostic Radiology tional Laboratory of Metrology of Ionizing

Radiation, Brazil.
It was developed the improvement of one
calibration procedure of mammography do- Instruments used in diagnostic radiology
simeters (ionization chambers) to be applied measurements can be tested in X radiation
at clinical X-ray system of the calibration qualities, using a Seifert X radiation system
laboratory (IPEN-CNEN/SP). The clinical X-ray (160 kV) and a reference system with four
system was studied in their behavior, or test- ionization chambers for diagnostic radiology
ed with respect to their response such as: measurements (mammography, computed
repeatability, reproducibility of the nomi- tomography, fluoroscopy, radiation protec-
nal voltage, current and air kerma rate. The tion and conventional diagnostic radiology
results obtained show the possibility to use ionization chamber) traceable to the PTB,
the clinical X-ray system in calibration pro- Germany (Fig. 47).
cedures. After those studies, one calibration
procedure of mammography dosimeters (ion-
ization chambers) was established at calibra-
tion laboratory.

Metrology in Diagnostic Radiology

The Calibration Laboratory has since 1980
been calibrating instruments used in radia-
tion protection and therapy measurements
and belonging to hospitals, industries, clinics
and other users located in São Paulo and in
other parts of Brazil.

Since 2000, calibration service is being offered
to users of diagnostic radiology instruments
with the establishment of standard radiation Figure 47 - X radiation calibration system.
quality at this level.
The types of instruments calibrated are: sev-
At the radiation protection level, there are eral kinds of ionization chambers, pen dosim-
137
special set-ups with gamma ( Co and Cs), eters, survey meters (including superficial
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beta ( Sr + Y, Tl and 147 Pm), alpha ( 241 Am, contamination detectors), alarm dosimeters,
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90
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233 U, 238 Pu, 244 Cm, etc.) and low energy X ra- clinical dosemeters and others. The distribu-
diations (60 kV). tion in terms of levels of calibration is: 13 %
for radiation therapy, 10% for diagnostic ra-
Clinical dosimeters (radiotherapy level) can diology and 77% for radiation protection level.