Imaging tech here. Remote logins from vendor service staff are very helpful when stuff breaks as they can order parts or suggest fixes without coming in. They also track things like helium levels and water temperatures. Problems in these areas can be very very expensive. Losing a hour can be a loss in thousands in revenue very easily, let alone a few weeks of scanner time and tens (or maybe even low hundreds) of thousands in helium and parts.

Other reasons for network connectivity include retrieving and sending image sequences and data files (basically the actual scans) which is done all day everyday.

The more alarming part is the retrieving of raw data which is the unreconstructed scan. This involves attaching a memory stick that is supposedly clean and uploading to that. Generally this stick is stuck into any old researcher PC and files are off loaded. Vendors don't particularly like this but getting 10-20 gig files off the scanner via command line is pretty clunky at the best of times.

Such devices absolutely should be isolated in separate networks (DMZs), and connections to outside world should be removed except for the bare minimum.

That the NHS has not done this is their actual failing and negligence. It doesn't take that much money to move such devices to a quarantined network.