MRI Billing

I need your help with some questions about radiology billing.  I am working with a doctor that sends his patients out to have xrays and MRIs in an outside facility.  The doctor wants some of his xrays and MRIs re-read (second opinion).  Can the facility/radiologist that is doing the re-read be reimbursed?  If so, how would we bill for the re-read after we've already billed for the MRI?
 
Also, we have a radiologist that we pay a flat fee of $50 per MRI that he reads for us.  Am I able to bill for each MRI result that he reads over and above the MRI CPT® code?
 
Your help with these two questions would be greatly appreciated.