- fMRI (Functional magnetic resonance imaging) : fMRI or Functional magnetic resonance imaging is the modified version of MRI that measures energies released by hemoglobin molecules in an MRI scan and then determines the brain areas receiving the greatest supply of blood and oxygen; an imaging technique that uses MRI equipment to examine blood flow in a noninvasive, nonradioactive manner. fMRI, moreover, is a method of studying brain activity by using magnetic fields to track blood flow in the brain; non-invasive method of discovering which areas of the brain are active as a subject performs a task by measuring blood flow as an indicator of neuronal activity.