Lesson Plan: Magnetic Resonance Imaging Physics

Students will be able to

• recall that a fundamental quantity called spin exists, where spin can be in either of two opposite directions,
• recall that, within a uniform magnetic field, the spin axis of an atomic nucleus precesses,
• recall that, for an object within an applied uniform magnetic field, the precession axes of nuclei of atoms of the object will align either with the direction of or against the direction of the magnetic field,
• recall that, for an object within an applied uniform magnetic field, there will be slightly more atoms of the object with nuclear precession axes aligned with the direction of the magnetic field than atoms with nuclear precession axes aligned against the direction of the magnetic field,
• recall that the nucleus of an atom in an object within an applied uniform magnetic field can be excited by absorption of a photon, changing the alignment of the precession axis of the nucleus from against the direction of the field to with the direction of the field,
• recall that the frequency of electromagnetic radiation that is most likely to excite an atomic nucleus is equal to the precession frequency of the nucleus,
• recall that the precession axis of an excited nucleus will spontaneously return to being aligned against the direction of a uniform magnetic field and that this is called deexcitation or relaxation,
• recall that an excited nucleus emits a photon with a frequency equal to its precession frequency when it relaxes,
• recall that magnetic resonance imaging can produce three-dimensional images of the interiors of objects,
• recall that magnetic resonance imaging involves excitation and then relaxation of atomic nuclei of atoms within a uniform magnetic field,
• recognize that production of useful magnetic resonance images of an object relies on variation of the magnetic field that the object is within.