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Innovative methodology for intercomparison of radionuclide calibrators using short half‐life in situ prepared radioactive sources
Author(s) -
Oliveira P. A.,
Santos J. A. M.
Publication year - 2014
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4884035
Subject(s) - radionuclide , calibration , reproducibility , radionuclide therapy , nuclear medicine , dosimetry , nuclide , environmental science , nuclear engineering , radioactive source , radiochemistry , materials science , medical physics , nuclear physics , physics , chemistry , optics , mathematics , medicine , engineering , statistics , detector , quantum mechanics
Purpose: An original radionuclide calibrator method for activity determination is presented. The method could be used for intercomparison surveys for short half‐life radioactive sources used in Nuclear Medicine, such as 99m Tc or most positron emission tomography radiopharmaceuticals. Methods: By evaluation of the resulting net optical density (netOD) using a standardized scanning method of irradiated Gafchromic XRQA2 film, a comparison of the netOD measurement with a previously determined calibration curve can be made and the difference between the tested radionuclide calibrator and a radionuclide calibrator used as reference device can be calculated. To estimate the total expected measurement uncertainties, a careful analysis of the methodology, for the case of 99m Tc, was performed: reproducibility determination, scanning conditions, and possible fadeout effects. Since every factor of the activity measurement procedure can influence the final result, the method also evaluates correct syringe positioning inside the radionuclide calibrator. Results: As an alternative to using a calibrated source sent to the surveyed site, which requires a relatively long half‐life of the nuclide, or sending a portable calibrated radionuclide calibrator, the proposed method uses a source prepared in situ . An indirect activity determination is achieved by the irradiation of a radiochromic film using 99m Tc under strictly controlled conditions, and cumulated activity calculation from the initial activity and total irradiation time. The irradiated Gafchromic film and the irradiator, without the source, can then be sent to a National Metrology Institute for evaluation of the results. Conclusions: The methodology described in this paper showed to have a good potential for accurate (3%) radionuclide calibrators intercomparison studies for 99m Tc between Nuclear Medicine centers without source transfer and can easily be adapted to other short half‐life radionuclides.