Calculation of calibration figures and the volume correction factors for 90Y, 125I, 131I and 177Lu radionuclides based on Monte-Carlo ionization chamber simulation method

Many metrology laboratories are dealing with activity measurements of different radionuclides with special interest in nuclear medicine as well as in radiopharmaceutical industry. In improving the accuracy of radionuclide activity measurements, a key role plays the calculation of calibration figures and the volume correction factors for the radionuclide under study. It is well known that the chamber calibration factors depend on the measurement geometry including the volume of the source and the type of the measurement vessel. In this work, the activity standards in the form of radioactive solutions are delivered in sealed Jena glass 5 ml FIOLAX-klar ampoule. Calculation of the calibration figures (or efficiencies) for 90Y, 125I, 131I and 177Lu radionuclides on 5 ml ampoule are presented in this paper. Additionally, their appropriate volume correction factors are determined. These calibration figures for the ISOCAL IV pressurized well re-entrant ionization chamber (IC) are pointed out based on the Monte-Carlo (MC) simulation method of such chamber using the PENELOPE-2005 MC computer simulation code. The chamber is filled with nitrogen gas pressurized to approximately 1 MPa. In determining the volume correction factors, the variation of calibration factors versus the mass of radioactive solution filling the 5 ml ampoule glass is investigated. From the point of view that impurity of 177mLu isomer is always accompanying the 177Lu radionuclide, for making possible the correction due to presence of this impurity, the calibration factor and the volume correction factors for 177mLu are reported as well