Contributed by alert reader Jan Dumont. A quote from an AT&T magazine called "Focus", c. 1989; the article was about a community hospital sending images of xrays to a regional hospital for expert advice.
A typical radiology image requires approximately 3.6 minutes to transmit over conventional telecommunications services. A total medical exam, consisting of between 40 and 60 images, would take hours to complete -- far too long in critical situations. ISDN speeds the transmission time to approximately 37 seconds per image.