Yep - deep breaths (but not too deep or it will hurt your ribs! :( )
How on earth did the MRI cause the fractures?
Fractured ribs are incredibly painful @CeeCee - and there is not a lot they can do other than painkillers xx I hope they gave you some 'good ones' to deal with the pain.
As it is often painful to breath - you have to be careful not to get congestion in the lungs (as they are probably not being fully inflated due to the pain) .... if the chest pain increases, see your GP asap xx