New procedures for radionuclide impurity determination and traceability of activity measurements of short-lived radiopharmaceuticals

摘要

New short-lived radionuclides ((beta)~(+)/~(-) and/or gamma-emitters) are extensively used in Nuclear Medicine both for diagnostic and therapeutic purposes. Radionuclide impurities ((beta)~(+)/~(-) and/or gamma-emitters, short- and long- lived) could be present with the medically useful radionuclide because of the specific production method used. Proper identification and quantification of these impurities is an important aspect in routine operation, as required by legal authorities. To provide the necessary metrological support to these measurements, the ENEAINMRI, Italian Primary Metrology Institute for Ionizing Radiation Quantities, started some years ago an intensive research program in the field of medical radionuclide metrology. The main aspects of this program were the development of the national standards and calibration procedures for medical radionuclides and associated impurities. To this regard, significant effort was put by the ENEA-INMRI to develop and implement a new method for impurity identification and measurement. The ENEA-INMRI method is applicable to mixtures of short-lived components. It has been initially developed for the standardization of beta-emitters and later on applied to nuclides with different decay scheme. It makes use of repeated count rate readings at different times, during nuclide decay. The collected readings are then analyzed by an appropriate code to obtain the individual radionuclides activities. A similar approach was applied to calibration of secondary standards, such as those based on well-type ionization chambers, in presence of radionuclide mixtures.