Quality Control and Testing of ^99mTc-Macroaggregated Albumin

Summary

^99mTc-labelled macroaggregated albumin particles prepared from a commercial “kit” have been tested in detail. With the introduction of the method of gel chromatography column scanning it became possible to make fast and simple quantitative measurements of the radiochemical purity. This was found to be the only reliable method for quantitative determination of non-aggregated ^99mTc-labelled albumin. The measuring results of the kit in question have shown a labelling efficiency of about 97—99%. In addition to a few percent of ^99mTc-pertechnetate less than 0.5% of disturbing radioactivity was found. The labelling was stable for at least 5—6 h. About 80% of the particles are in the size-range of 10—80 μm. A rough estimation of the number of particles in the solution resulted in 0.4 · 10⁶ per mg of MAA.

The dynamic studies of the lung uptake and the elimination of ^99mTc-MAA in man resulted in a biological half-time in the lungs of about 1—2 h. The radiation absorbed dose to the lungs per mCi administered ^99mTc-MAA was estimated to 0.1 rad. Less than 1% of the radioactivity was accumulated in liver, spleen or kidneys during the first 25 minutes after injection.

^99mTc-markierte Albumin-Makroaggregatpartikel, die aus einem „Kit“ hergestellt wurden, sind im Detail geprüft worden. Mit der Methode Gelchromatographie Säulen Scanning ist es möglich, schnelle und einfache quantitative Messungen der radiochemischen Reinheit durchzuführen. Die Markierungs-Effektivität dieses Kits ist ungefähr 97—99 %. Außer einigen Prozenten des ^99mTc-Pertechnetates wurde weniger als 0,5% von anderen radioaktiven Bestandteilen als Makroaggregat gefunden. Die Markierung war länger als 5—6 Stunden stabil. Ungefähr 80% der Partikel hatten eine Größe von 10—80 μm. Eine ungefähre Schätzung der Anzahl der Partikel in der Suspension ergab 0,5 · 10⁶ per mg MAA. Dynamische Untersuchungen der Aufnahme und Eliminierung von ^99mTc-MAA in den Lungen ergaben eine biologische Halbwertzeit in den Lungen von ungefähr 1—2 Stunden. Die Strahlenbelastung der Lungen beträgt 0,1 rad per mCi verabreichten ^99mTc-MAA. Weniger als 1% der verabreichten Radioaktivität wurde in der Leber, Milz oder in den Nieren während der ersten 25 Minuten nach der Injektion kumuliert.

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