Dear Ocaders,
I have a question in my mind, for a long time
Sometimes the images postcontraast show signal drop when i compare them with precontrast
So…when i have some blood like in this morell lavalle lesion, when i give contrast, suddenly the very bright blood is not so bright anymore.
Somentime the difference is not important when measured, but visually striking
But sometimes I get hundreds of units difference
So…. Is it just an optical illusion? (I used the same window/brightness, but could be this kind of illusion https://en.wikipedia.org/wiki/Checker_shadow_illusion)?
Or there sequences are somewhat tuned automatically after contrast (even the parameters are the same, I checked).
This could apply to Ct I guess, when due to increase density after contrast, the machine will increase the parameters, but in MRI I am not aware of this kind of modifications
Thank you in advance!
Sorin
