Perfusion Lung Scan - Artifact

Perfusion lung scan - Tc99m MAA

Images obtained on two consecutive patients demonstrated mild uptake in the salivary glands, thyroid and stomach. This represents free technetium due to either poor kit preparation or kit breakdown.  According to the package insert no less than 90% of the pertechnetate added to a reaction vial is bound to aggregate at preparation time and remains bound throughout the 6-8 hour lifetime of the preparation (depending on the manufacturer).

Use of Tc MAA after 8 hours of kit preparation has been shown to have an increase in agglomeration. It is recommended  for preparation and use of Tc 99m MAA, that  a fresh dose should be used for imaging.

The lower image demonstrates mild uptake int he stomach. If the ventilation portion of the scan had used Tc99m DTPA aerosol the stomach uptake could be accounted for by swallowed radiopharmacuetical. However at this facility the ventilation portion of the study was acquired utilizing Xe133.