After ct scan what is duration of contrast medium (iodine) in body?

Are you sure.: If radio active iodine is used it is i-131 which has half life of less than 9days, then calculate every 9 days half of it will be eliminated in the body with i -131. Not bad if we did not synthesize i- 131 imagine if it is i- 129 which had half life of 15.7 million years.

Depends: Oral or IV contrast. Oral few days. Iv day or two depending on type of contrast.