Well, if you're not having the MRI done at a hospital, they might have only so many techs around that could keep trying to do the IV.

My MRI's were all done at imaging centers. My first one was done at a larger center, but they still had only one machine, but they seemed to have a lot of extra techs around. They didnt have a problem with the IV there.

The other one was done at a smaller imaging center, they had two techs. One was new, and the other guy had been there forever. He had the best luck with my failed IV. He was able to get a little contrast in, just before the vein collapsed or quit working, whatever you call it when it cant get the contrast in. He let the new person attempt the IV in my other arm, and the back of my hand, he tried it too in the back of my other hand. They just couldnt get the contrast in there.

I didnt blame the techs for not being able to get the contrast in. (it was the nurse from the day before's fault, she ripped my veins apart in my elbows taking blood. Most painful blood draws I've ever had!) I think there are probably times when they just cant get the contrast in. I had to go back a week later for another MRI to confirm the little blips they saw on the first one as being lesions.

By then the ripped up veins in my elbows were healed and they had no problems with getting the contrast in. That pretty much confirmed to me to not have an MRI done the day of or day after having blood drawn.