The trial is not just a test to see whether doctors can read a...

The trial is not just a test to see whether doctors can read a colourised xray; that's the easy part.
Each institution/hospital will be trialling the end to end process, this would have to involve secure connectors into the hospital's patient data repository.

I work in a large organisation where customer data is central to our business and the amount of effort involved in protecting and monitoring this data to keep it secure is insane. Each time we set up data flows into "the cloud" involves infrastructure and Application Architects, Information Security approvals, Data Privacy checks/audits etc. - and this is all before any actual technical work commences. Then there's the Proof of Concept stage where test systems are built in parallel to production systems to ensure that the process works as expected. Then we move to building the live/production system, testing, then implementation. This can take several months to sort out if even if it's the number one priority for the organisation...and I'm guessing for many hospitals it's not. It gets worse if the cutomer data is stored in old, bespoke systems that are managed by third party vendors and are hard to work with.

My point is this: there's a lot that has to happen in the background for these trials to move to the stage where contracts are signed, and a good deal of the work needs to be done by the hospitals, at their pace.