<prompt> Which of the following imaging techniques is best able to measure regional brain substrate uptake and metabolic kinetics?magnetic resonance imaging MRIcomputed tomography CTpositron emission tomography PETserial thallium scintigrams  <response>: PET scans use glucose analogues to demonstrate metabolic activity. They are rarely available, however, and functional MRI scans are now being used extensively to assess areas of brain activity. 