Contrast is flushed out through the kidneys. For this reason drink water before the MRI (not too much for obvious reasons) and drink a lot of water after the MRIs. If you do this the contrast is out of your system after the second time you urinate.
The whole set of MRIs ordered will initially be done without contrast. After those they will inject the contrast, put you back in, take the MRIs, and you're done. The contrast MRIs are done much quicker than the ones without. The contrast will not show anything that the non-contrast MRIs show. Contrast allows, in MS, to show active lesions.
My suggestion: Do the MRIs as ordered for the most comprehensive scans/report.
Diagnosed with Multiple Sclerosis in 1985
CPTSD diagnosed Feb 2004 (PTSD since age 2), Anxiety/Panic attacks secondary to PTSD.