Functional magnetic resonance imaging (fMRI) was a process which measures the change in blood flow in the brain, as it related to neural activity. It worked by observing the effect of magnetic fields on oxygenated and deoxygenated hemoglobin.
In Kornak medical science, fMRI technology was sophisticated enough to use as a lie detector, by reading real-time neurological changes during the questioning of a subject. Part of what made this effective was the presence of methemoglobin, rather than hemoglobin, in the Kornaks' species' blood. Still, Doctor Idit Kahayn believed the Kornak fMRI would work on Julian Bashir's unique biochemistry. (SCE eBook: Wounds, Book 2)