Quality Control Troublshooting

We have three cameras in my department. I completed the first intrinsic flood (2million counts) when I noticed the uniformity on detector 2 was not good. I decided to move on to the next camera and come back to determine the problem, since the pattern was not typical of most non-uniformity problems.

The second camera demonstrated a similar, but more intense non-uniformity issue with detector 2. Coincidence... Now I had to determine the problem. I removed the source from the area and started a uniformity flood without a source to see if there was contamination in the area. A previous episode had a hot needle in a nearby sharps container. This time nothing was initially found.

I then checked my discarded gloves, which I Usually place on top of the collimator cart after placing the source and removing them...

In the first room my gloves were placed at the back of the collimator cart, so the activity on the glove was attenuated by the cart. In the second room, to which I carried my gloves (I dispose of them in the hot lab after completion of acquiring all morning uniformities) and had placed them at the front of the cart. Without the attenuation from the cart, the "extra" source is predominant in the acquired image...

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.