The best choice for identifying anatomical functioning without using any type of dye or tracer would be MRI (Magnetic Resonance Imaging).
MRI is a non-invasive imaging technique that provides detailed images of the brain's anatomy without the need for any tracer or contrast agent, unlike PET and SPECT, which do require radioactive tracers. EEG (Electroencephalography) measures electrical activity but does not provide detailed anatomical images. Therefore, MRI is the most appropriate option in this context.