engleski

Upgrade of the Canberra Accuscan in vivo Whole Body Counting System

Canberra Accuscan whole body counter is a horizontal bed geometry in vivo counting system for assessing the internal contamination with gamma emitting radionuclides. It comprises of two detectors (one 10x10x41cm large sodium iodide NaI(Tl) scintillation detector and one high purity HPGe semiconductor detector with 20% relative efficiency). Detectors were originally connected to Canberra’ s analogue nuclear instrumentation modules (NIM) and multichannel analyzer. Spectra were acquired and analyzed by DEC Micro-PDP 11/73 computer. Dedicated ABACOS-II software was installed for gamma-spectroscopic and dosimetric purposes. A calculation of the internal effective doses was performed according to the ICRP-2 and ICRP-30 recommendations. Recently, the system was upgraded due to the breakdown of the old computer system. The following components were added: two DSA-1000 desktop spectrum analyzer units integrating multichannel analyzers based on digital signal processing ; MS Windows based workstation for acquiring and analyzing spectral data by dedicated GENIE 2000 gamma analysis software and ABACOS 2000 whole body counting software. Complete new energy and efficiency calibrations of the upgraded system were performed using a mixed source of radionuclides emitting gamma rays within the energy range of 88-1836 keV. The mixed source was placed onto the bed or into the anthropomorphic REMCAL phantom on bed to simulate and obtain counting efficiencies of various practical geometries (bed surface, thyroid, lung, gastrointestinal tract) and various arrangements (scanning or static). Energy and counting efficiency calibrations of the upgraded whole body counting system will be compared with the initial original values, as well as with the minimum detectable activity (MDA) levels.

internal dosimetry; whole body counter; dose assessment

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