Development and validation of an alternative procedure for quantitative quality control analysis of 99mTc-radiopharmaceuticals using a Geiger Müller counter.

BACKGROUND AND OBJECTIVES: In a hospital radiopharmacy with 2a operational level, including the preparation of radiopharmaceuticals from prepared and approved reagent kits, it is common to have a single activimeter or dose calibrator for labeling and fractionation, and to perform the quality controls of the 99mTc-radiopharmaceuticals. In certain cases, the accumulation of radioactive material or accidental contamination of the work area causes the background to exceed the limits to carry out the radiochemical purity analyses and it is necessary to look for viable alternatives. In this work, a Geiger Müller detector (equipped with a probe for measuring surface contamination) frequently used for radioprotection purposes, was validated as an alternative and its performance was compared against the activimeter for 99mTc-radiopharmaceuticals. MATERIALS AND METHODS: Using [99mTc]pertechnetate, systematic studies of error analyses and detector response to activity concentration, activity and measurement time were carried out in liquid matrices and in paper. The results were compared against an activimeter calibrated for [99mTc]Tc. RESULTS: The developed method was used to determine the radiochemical purity of the compounds [99mTc]Tc-MDP and [99mTc]Tc-MIBI by ascending paper chromatography tests, obtaining comparable values to those measured with an activimeter in the same system (within 1% uncertainty) and using the method of vial partitioning in a dedicated equipment. CONCLUSIONS: This work demonstrates that a Geiger Müller detector with a probe for measuring surface contamination can be adequately used to replace other equipment in the control of radiochemical purity in the hospital radiopharmacy.

Amorphous calcium carbonate in the shells of adult Unionoida.

Shells of adult individuals from two different bivalve families, Hyriopsis cumingii and Diplodon chilensis patagonicus, were studied by Micro-Raman spectroscopy and Focussed Ion Beam-assisted TEM. The shells contain amorphous calcium carbonate in a zone at the interface between the periostracum and the prismatic layer. In this area, the initial prism structures protrude from the inner periostracum layer and it is demonstrated that these structures systematically consist of highly disordered and amorphous calcium carbonate. Within this zone, ordered and disordered areas are intermingled discounting the existence of a crystallization front and favouring models of domainal crystallization processes via so-called mesocrystals. These observations are the first documentation of the use of amorphous calcium carbonate as a precursor phase by adult mollusc species and lend further support to hypotheses postulating widespread use of amorphous phases as building material of skeletal tissue in biology.

Manganese speciation in Diplodon chilensis patagonicus shells: a XANES study.

X-ray absorption near-edge spectroscopy (XANES) at the Mn K-edge was used to investigate the environment of Mn in situ within the growth increments of the long-lived freshwater bivalve species Diplodon chilensis patagonicus. Single XANES spectra and Mn Kalpha fluorescence distributions were acquired at submillimetre resolution (up to 100 microm x 50 microm), at Mn concentrations below the weight percent range (100-1000 microg g(-1)) in a high Ca matrix. The position and intensity of the pre-edge feature in the shell spectrum resembles best that of the Mn(II)-bearing reference compounds, suggesting that this is the oxidation state of Mn in the bivalve shells. By comparison with the XANES spectra of selected standard compounds, hypotheses about Mn speciation in the shell are also reported. In particular, different factors, such as provenance, ontogenetic age, variable Mn-concentrations or seasonal shell deposition seem not to influence the speciation of the metal in this bivalve species.