Which of the Following Statements Most Accurately Describes Positron Emission

Which of the following statements most accurately describes positron emission tomography?

A) Technique in which a magnetic field is generated by electrical currents that are detected by sensors on the scalp
B) Technique used for measuring the electrical activity of specific brain regions in response to a particular stimulus
C) Technique that measures the diffusion of water molecules through neural tracts that's connect brain structures
D) Technique that measures metabolic activity of the brain through a radioactive substance