Rapid Decomposition of 99mTc-MAA Complex During Lung Perfusion Imaging.

A 30-year-old woman with a recent episode of dyspnea was presented. The lung perfusion scan using Tc-MAA (macro-aggregated albumin) initially revealed an acceptable lung-to-background activity ratio implying a proper radiopharmaceutical preparation and radiolabeling efficiency. Unexpectedly, later during the scan, rapidly increasing concentration of activity was observed in salivary glands, thyroid and stomach. Rapid breakdown of Tc-MAA complexes was considered as a likely explanation for the increase in the circulatory level of the free pertechnetate.