CT scan of admonen/pelvis with contrast

[dop89]

When a CT scan is done do they take into account the body size of the patient.So for someone slimmer having a abdomen/pelvis can the radiation dose would be small then for someone who is larger?Is there anything I can do limit the impact of the ionising radiation?Does some of the radiation come out in urine/facaes with the contrast medium?I know the mdeium isnt radiative but as it willl have taken a shot would this then have become radiatactive?Should the radiologist be providing with me any additonal shielding to minimise the radiation to other parts of my body?