Calibration of the LDI/CDTN Whole Body Counter us-ing two physical phantoms

Fernanda Guerra Paiva,Bruno Melo Mendes,Telma Cristina Ferreira Fonseca,Marco Aurélio Lacerda,Teógenes Augusto Da Silva,Sônia Prates,Bernardo Maranhão Dantas,Nelson Nascimento Filho,Jaqueline Rosária Pinto,Ana Letícia Dantas

doi:10.15392/bjrs.v5i3.252

Abstract

The Laboratory of Internal Dosimetry of the Center for Development of Nuclear Technology (LDI/CDTN) is responsible for routine monitoring of internal contamination of the Individuals Occupationally Exposed (IOEs) at the Unit for Research and Production of Radiopharmaceuticals (UPPR/CDTN), the Research Reactor TRIGA-IPR-R1/CDTN and other workplaces of the institute where there is a risk of accidental intakes. Additionally, LDI supports the Institute of Radiation Protection and Dosimetry (IRD/CNEN) to attend radiological emergencies. The determination of photon emitting radionuclides in the human body requires the use of calibration techniques in different counting geometries for converting the count rates into activity in organs and tissues. This paper presents and discusses the calibration of the LDI/CDTN Whole Body Counter (WBC) using a standard BOMAB phantom (Bottle Mannequin Absorber) compared to a home-made phantom produced with Polyethylene Terephthalate bottles (PET). Initially, the BOMAB was filled with a cocktail containing 60 Co, 137 Cs and 133 Ba. The phantom was counted at the LDI whole body counter and an Efficiency x Energy curve was obtained. Subsequently the PET-BOMAB was filled with the same standard source and a second curve was determined. The efficiency values in each region of interest as well as the shape of both curves were found to be equivalent. The results validate the use of the PET-BOMAB for the calibration of whole body geometry applied to the measurement of high energy radionuclides in the energy region evaluated in this work.

Highlights

The identification and quantification of photon-emitting radionuclides in the human body can be performed by means of in vivo measurement techniques
This paper presents and discusses the calibration of the Whole Body Counter systems (WBC) system installed at the Laboratory of Internal Dosimetry of the Center for Development of Nuclear Technology (LDI/CDTN) using a BOMAB phantom in comparison of a low cost physical phantom produced with Polyethylene Terephthalate bottles (PET)
The slight differences observed in counting efficiencies when comparing the BOMAB with the two versions of the PET-BOMAB are probably related to the size and weight of the phantoms which affect the irradiation geometry

Summary

Introduction

The identification and quantification of photon-emitting radionuclides in the human body can be performed by means of in vivo measurement techniques. When the detector is placed to cover specific organ or region of the body it should be pointed where the highest counting efficiency is expected, for example, the torso or pelvis of the monitored worker [2]. The subject is counted for a certain period of time, and the spectrum analysis allows the identification and quantification of the radionuclides in the body. The accuracy of the measurement relies on the quality of the calibration in regard to the distribution of the radionuclide in the whole body or in various organs and tissues compared to the individual biotype. Calibrations usually refer to a standard human being or groups of individuals or populations, established by the International Commission on Radiological Protection [5]. This paper presents and discusses the calibration of the WBC system installed at the Laboratory of Internal Dosimetry of the Center for Development of Nuclear Technology (LDI/CDTN) using a BOMAB phantom in comparison of a low cost physical phantom produced with Polyethylene Terephthalate bottles (PET)

Methods

Results

Conclusion