Is it possible for a ct contrast to identify a 1 mm tumor?

Not with certainty: CT scan can image and show small tumors down to 5-10mm depending on the anatomical location of the tumor mass. In the lungs, CT scan is the best test and can pick up/detect lesions as small as 3-4mm. But anything less than 2 mm is too small to pick up Cancer with certainty. We frequently end up doing a follow up CT scan in 2-3 months in order to detect further growth(Likely cancer) or lack of it