Question

Neutrons have a magnetic dipole moment and can undergo spin flips by absorbing electromagnetic radiation. Why, then, are protons rather than neutrons used in MRI of body tissues?

Short answer

There are virtually no free neutrons in the body, and the location of those few has zero biological significance.

Step-by-step solution

Important Concepts

The Hydrogen atom has one electron and one proton and zero neutrons in it.

Application

There are virtually no free neutrons in the body and the location of those few has zero biological significance. The free protons are${}_1{}^{1}H$ in the organic molecules and water, whose density has biological significance.