What are the criteria for removal of a greenfield filter had two clots in the last two years lungs?

None: I dont think there is ever a reason to remove, unless it gets infected or there is some other mechanical failure. If you had 2 dvt's in the last year, why would you want to remove a protective mechanism such as this?

Filters: Can be removed. First you need to see if yours is truly removable. If not, then it is a moot point. If you are having clots, you need a work up for thrombophilia or thick blood. If you do need your filter removed you must have a leg doppler and ivc gram to make sure it is safe.