Answer:
functional magnetic resonance imaging or fMRI
Step-by-step explanation:
fMRI or Functional MRI is a technique used in medical treatment which measures the brain activity by identifying the changes associated with the blood flow. The fMRI technique depends upon the fact the neuronal activation and the cerebral blood flow are coupled.
The full form of fMRI is functional magnetic resonance imaging.
In the context, Dr. Charles uses the technique of fMRI to conduct brain scans using radio waves.