In my experience, a regular CT can't even pick up a 5 mm or so liver thing. It's too small. A multiphase CT may be able to. An MRI definitely can. But none of them, not even the MRI, can definitively say what they are and whether they are malignant. Only a biopsy can do that. And for a spot that small, it likely makes more sense to just remove it, depending on where it is in the liver. But even if it is on the surface of the liver, like my little mass, they are likely to say that it isn't worth even the small risk of liver injury unless it changes. Which is why my little liver thing is still there, but after 2+years of no change at all is considered to be something inert. So I am NED.
BTW, it is my understanding that a PET scan has the same size constraints as a CT scan, so if a mass is tiny it is not likely to pick it up.
Please note that everything I've said pertains strictly to VERY SMALL liver masses. Under a cm.
F, 64 at DX CRC Stage IV
3/17/18 blockage, r hemi
11 of 25 nodes,5 mesentery nodes
5mm liver met out
pT3 pN2b pM1
BRAF wild, KRAS G12D
7/18 and 11/18 CT NED
12/18 MRI 5mm liver mass, 2 lymph nodes in porta hepatis
6/19 Multiphasic CT LNs normal, Liver stable
6/28/19 Pause Key, predisone for joint pain
7/31/19 Restart Key
9/19 CT stable
Pain: all fails but Celebrex
12/23/19 CT stable
5/19 MRI stable/NED
8/20 MRI NED