I work in an imaging veterinary center and we do scans that can run 2 hours. We scan some rather critical pets and take the best precautions. The patients are placed on a ventilator, anesthesia constantly monitored and they packed in blankets to keep them warm during the procedure. If at anytime the patient appears to be at question the scan is halted and the patient checked. I suggest to call the mri center you are considering going to and ask of their protocol-I imagine it’s much of the same.