BACKGROUND: 99mTc-phosphate and ^99mTc-IDA complexes, made by the addition of ^99m TcO₄ – to the kits, have been applied to bone and gallbladder imaging respectively, for many years. In this paper, an effort to label DPD and EHIDA with [^99mTc(CO)₃(H₂O)₃]+ was carried out.
MATERIAL AND METHODS: DPD and EHIDA were synthesised and prepared in kit form in INS “Vinca”. A carbonyl labelling agent IsolinkTM (Mallinckrodt Medical B.V.) and a carbonyl precursor (NCRS Demokritos) were applied. The samples of each compound were added to a vial containing ^99mTc-carbonyl precursor, in which original pH (10÷11) was neutralised to a pH of around 5.5 or 7.5, the same one as the pH of the investigated compounds. After heating, the reaction products were analysed by HPLC equipped with UV and g-detector, with TEAP 0.05 M, methanol and water as solvent. The biological evaluation of ^99m99mTc(I)-coordinated compounds, as well as ^99mTc-DPD and ^99mTc-EHIDA complexes, involved a bio distribution examination on Wistar rats.
RESULTS: The results have shown that hydrophilic organometallic [^99mTc(CO)₃(H₂O)₃]+ precursor facilitates the formation of Tc (I) complexes with these ligands, based on the tricarbonyltechnetium (I) core. The changes in structure of DPD and EHIDA labelled molecules influenced biological behaviour: ⁹⁹Tc(CO)₃ -DPD did not accumulate in bone (< 1% of the complex was found in the femur), while ⁹⁹Tc(CO)₃ - EHIDA has shown slower billiary excretion and faster filtration through the kidneys.
DISCUSSION: The results of the labelling of DPD and EHIDA with [^99mTc(CO)₃(H₂O)₃]+ and their chemical and biological behaviour, in comparison with the same one for ^99mTc-DPD and ^99mTc-EHIDA, confirmed that different oxidation states of technetium make the formation of a variety of complexes with quite different behaviour possible.