According to SecurityLedger.com:
"Radiologic and medical imaging systems such as the PACS were particularly useful because they are heavily used and critical to the operation of almost every department. Of the three systems that TrapX found infected at customer sites, one was a PACS, the second was a medical x-ray scanner and the third was a collection of blood gas analyzers in a healthcare institution’s laboratory department used by critical care and emergency services."
The answer to all of this of course is for hospitals to insist that manufacturers include high quality encryption and security features on all of their devices. Even then, it is likely that it could be several technology life-cycles before the majority of the older and vulnerable imaging machines are upgraded or decommissioned. This is one of the reasons that it is vital that hospitals keep up with their scheduled technology upgrades and modify those schedules in response to security threats as needed.
For more information, view SecurityLedger.com coverage of the report: