Catphan 604 CTP515 low contrast visibility 1% ROIs only

Hi all,

I’m hoping to use pylinac to measure the low contrast visibility on the CTP515/CTP730 module. Can I ask the reason that only the 1% ROIs are examined? Is it a limitation of the method used? Or can the user add the other ROIs?
We usually record the 0.5% and 0.3% ROI values when doing this test manually.



I’d be interested to know what other pylinac users have done for this test.

Do you ignore the other rods on the low contrast module (CTP515 or 730) and just analyse the 1% contrast levels? Or perhaps analyse them manually or use a different method?

I assume there is a good reason that pylinac doesnt analyse the 0.5% and 0.3% constrast ROIs but I can’t find it in the manuals.