It's not stated in the article, but I assume the CT scan is done on-site (i.e., not in a moving ambulance), meaning the patient is not being transported to the hospital. So if the time needed to do the CT is less than the time to transport the patient to the hospital (and there's no waiting at the hospital for CT access, etc.), the therapy can be started on-site (after the delay for the CT scan), etc. It's a costly, time-consuming service, but faster than waiting. I'm still waiting for an on-site bed-side dip-stick blood-based test that can differentiate the metabolite(s) released after an ischemic blockage from those of a hemorrhagic stroke.