Hello~When you had the MRI, was your neck in an awkward position? Were you maybe subconsciously holding your-self tight. The reason I ask is because if your neck is out of alignment due to these things, you will have the dizziness, it is not related to the procedure, but how your body handled the stress.
I would see a chiropractor and ask him/her if this could be the case, he/she will probably take an x-ray of your neck, this will show any misalignment or pinched nerves, after a few adjustments, you should start feeling better in no time.
I hope you feel better soon. God bless you.