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49
ST 1.1 –
Dosimetría interna
CALIBRATION OF IN VITRO BIOASSAY METHODOLOGY FOR
DETERMINATION OF
131
I IN URINE
Carvalho, Carlaine
1,2
; Hazin, Clóvis
1,2
; Lima, Fabiana F.
2
*
1
UFPE, Brasil.
2
CRCN-NE/CNEN, Brasil.
* Autor responsable, email: fflima@cnen.gov.br
The use of unsealed radioactive sources in institutions practicing Nuclear Medicine poses a
significant risk of internal exposure of workers. In this context, handling of
131
I plays an important
role in relation to other radionuclides due to its wide application, particularly in medical diagnosis
and therapy of diseases related to the thyroid gland. Given the increasing number of services
using
131
I in their examination protocols, the probability of accidental incorporation of this
radionuclide has increased. The present study aimed to implement methodologies for in vitro
bioassay at the Centro Regional de Ciências Nucleares do Nordeste (CRCN-NE/CNEN) for
internal monitoring of individuals occupationally exposed to
131
I. For in vitro system calibration, a
coaxial HPGe detector model GC1018 and a standard
133
Ba source were used. Upon obtaining
the calibration factor, it was possible to determine the minimum detectable activities (MDA) for
the system by using direct measurements of distilled water simulating urine (in vitro). Then, by
using the biokinetic models provided by the International Commission on Radiological
Protection, edited with the AIDE software version 6.0, it was possible to estimate the Minimum
Detectable Effective Dose (MDED). MDED values obtained were compared to the record level of
1 mSv recommended by the International Atomic Energy Agency in the urine compartment 24 h.
The values found were lower than the record level of 1 mSv in all simulated incorporation
scenarios: inhalation of vapor and particles with AMAD of 1 µm and 5 µm, type F compound,
and ingestion. The results of this work show that the implemented technique is suitable for
conducting internal monitoring of workers to
131
I. It is intended to continue the work aiming the
monitoring of occupationally exposed individuals from Nuclear Medicine Services in Recife –PE.