Lung Scan - renal uptake

Clinical history: 85 y-male arrived in nuclear department for a lung scan to rule out pulmonary embolism.

Technique: Patient received 20 mCi Xe133 ventilation, followed by 30 mCi Tc99m MAA for lung perfusion imaging.

There was renal uptake noted on the perfusion images which was an unexpected finding. Following investigation it was found that the patient had come into the medical center the previous night through the emergency room and a lung scan had been started. Due to equipment malfunction the perfusion portion of the scan was not completed, and was to be repeated the following morning. The uptake by the kidneys was determined to be most likely due to biological breakdown of the Tc99 MAA from the previous night, which was being removed from the body through the kidneys.
Thanks to Cheryl Casale, 2004.

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.