Measures are needed to stop brain scans being misused by courts, insurers and employers, experts have warned.
Scans can show a person's reactions by demonstrating if certain areas of the brain "light-up".
At least one US company is offering scans to employers recruiting staff but American courts have already rejected attempts to use scans in cases.
The University of Edinburgh's Burkhard Schafer said there were issues over privacy and reliability of technology.
The subject is being discussed by experts from around the world at a University of Glasgow conference.
'The next frontier'
Attempts have been made to use MRI scans as lie detectors or to demonstrate mental health problems in more than 90 capital punishment cases in the US, as well as in other hearings in Europe and Asia.
As soon as public awareness increases there will be interest from everyone from daytime entertainment programmes to employers and the legal system
While they have been rejected in many cases, scan results have sometimes been accepted as evidence.
Mr Schafer, co-director of the SCRIPT Centre for Research in Intellectual Property and Technology at the University of Edinburgh's school of law, said the UK had to consider how to prevent MRI scans being misused - and how to protect people's privacy.
"After data mining and online profiling, brain imaging could well become the next frontier in the privacy wars.
"The promise to read a person's mind is beguiling, and some applications will be greatly beneficial.
"But a combination of exaggerated claims by commercial providers, inadequate legal regulation and the persuasive power of images bring very real dangers for us as citizens."
He added: "As soon as public awareness increases there will be interest from everyone from daytime entertainment programmes to employers and the legal system.
"It would be sensible to be prepared."
'Powerful and compelling'
Mr Schafer added there was also a chance employers could seek to use scans to test the honesty of an individual's CV - or by insurance companies.
We do need to have an informed debate
"There should probably be a moratorium for insurance companies, as has happened over the use of genetic test information."
But he warned MRI scans should not be used in this way: "The science isn't there."
Joanna Wardlaw, professor of applied neuroimaging at the University of Edinburgh, said brain scans could show differences between groups who thought differently in a research setting.
But she added: "It's very, very difficult to apply the results of an individual's scan in situations such as where there is a threat of legal action.
"Images are powerful and compelling, and people are likely to accept them. But there needs to be much more understanding of what the limitations are."
Professor Geraint Rees, director of the University College London's Institute of Cognitive Neuroscience, said: "I'm concerned about the potential use of scans that are starting to emerge now, but whether we need to go down the road of legal regulation, I'm not so sure about.
"But we do need to have an informed debate."