image sourceBBC News/Cambridge Universityimage captionAI can identify patterns in brain scans even the most expert neurologists cannot see.
Scientists are testing an artificial-intelligence system thought to be capable of diagnosing dementia after a single brain scan.
It may also be able to predict whether the condition will remain stable for many years, slowly deteriorate or need immediate treatment.
Currently, it can take several scans and tests to diagnose dementia.
The researchers involved say earlier diagnoses with their system could greatly improve patient outcomes.
"If we intervene early, the treatments can kick in early and slow down the progression of the disease and at the same time avoid more damage," Prof Zoe Kourtzi, of Cambridge University and a fellow of national centre for AI and data science The Alan Turing Institute, said.
"And it's likely that symptoms occur much later in life or may never occur."
Prof Kourtzi's system compares brain scans of those worried they might have dementia with those of thousands of dementia patients and their relevant medical records.
The algorithm can identify patterns in the scans even expert neurologists cannot see and match them to patient outcomes in its database.
In pre-clinical tests, it has been able to diagnose dementia, years before symptoms develop, even when there is no obvious signs of damage on the brain scan.
The trial, at Addenbrooke's Hospital and other memory clinics around the country, will test whether it works in a clinical setting, alongside conventional ways of diagnosing dementia.
In the first year, about 500 patients are expected to participate.
Their results will go to their doctors, who can, if necessary, advise on the course of treatment.
image sourceBBC Newsimage captionDenis and Penelope Clark want to know how his condition will progress, so they can plan for their future
Consultant neurologist Dr Tim Rittman, who is leading the study, with neuroscientists at Cambridge University, called the artificial-intelligence system a "fantastic development".
"These set of diseases are really devastating for people," he said.
"So when I am delivering this information to a patient, anything I can do to be more confident about the diagnosis, to give them more information about the likely progression of the disease to help them plan their lives is a great thing to be able to do."
Among the first to participate in the trial, Denis Clark, 75, retired from his job as an executive for a meat company five years ago.
Last year, his wife, Penelope, noticed he was sometimes struggling with his memory.
And they are now concerned he is developing dementia.
Denis tries to describe his symptoms but Penelope interjects to say he finds it hard to explain what is happening.
The couple are worried about having to sell their home to fund Denis's care.
So Penelope is relieved they should not have to wait long for a diagnosis and an indication of how any dementia is likely to progress.
image sourceBBC Newsimage captionNormally, Denis might need several brain scans to see whether he has dementia
"We could then plan financially," she said.
"We would know whether as a couple we could have a few holidays before things get so bad that I can't take Denis on holiday."
Another of Dr Rittman's patients, Mark Thompson, 57, who began having memory lapses 10 months ago, before the trial of the artificial-intelligence system began, said it would have made a big difference to him had it been available.
"I had test after test after test and at least four scans before I was diagnosed," he said.
"The medical team was marvellous and did everything they could to get to the bottom of what was wrong with me.
"But the uncertainty was causing me more… mental problems than any caused by the condition.
"Was it a tumour? Would they need to operate? It caused me so much stress not knowing what was wrong with me."
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