What Causes Burning And Shooting Pain Down My Calf Muscles?

had MRI 2008, brain. Injection ok but, searing, burning pain shoot down side of calf for about 15 seconds. Techs weren't too concerned. 2009, different MRI place would not do contrast after I told them about calf. I have to have MRA MRV and i know contrast is better. Im so sick, Im asking if this was just sensitivity? One time thing or allergy. can you help?