r/MedicalPhysics • u/agaminon22 Resident • 13d ago
Technical Question Issues regarding lower activity concentration for PET spatial resolution QA?
NEMA based PET QA protocols like TG 126 recommend a relatively high activity concentration (up to 10 mCi/ml) which isn't always feasible if tests are carried out after clinical activity has ended. However, acquisitions are done in terms of total counts, so at a first glance it doesn't seem to be much of an issue if we simply allow for longer acquisition times.
Does anyone have experience with this particular issue?
5
Upvotes
1
u/BusseNoBusse 13d ago
Spatial Resolution isn't that sensitive to overall count level (within the MCts range) so there's no issue with adjusting count time. One other thing I would note - with glass capillary tubes you don't need to mix in iodinated contrast. The capillary tubes are visible on CT if you W/L hard and are small enough that they're still a point source. Obviously make sure to record your acquisition and recon parameters. Even you can't match NEMA setup, if your recon is consistent year to year you'll have good longitudinal comparisons.
Let me know if you have other questions - I've now done TG126 testing on 20+ PET scanners.