Do neurons look identical to each other?

NO, NEURON DO NOT LOOK IDENTICAL TO ONE ANOTHER.
Neurons are specialized cells which transmit nerve impulses in living organisms. Neurons generally share basic structural characters and theme, but they are not exactly alike. All neurons are different from one another but they possess a common structural theme. In this case, neurons can be compared to plants; all plants have roots, stem, branches and leaves but not all plants are the same.

Is this used on a test? ?

Unlike  ct scans, which use x-rays,  mri scans  use powerful magnetic fields and radio frequency pulses to produce detailed pictures of organs, soft tissues, bone and other internal body structures.  differences between  normal and abnormal tissue is often clearer on an  mri  image than a  ct.you can see more with a mri scan. for example on an mri you can see internal bleeding.