Magnetic resonance (MR) scanner (A-level only)

Basic principles of MR scanner;

• cross-section of patient scanned using magnetic fields

• protons initially aligned with spins parallel

• spinning hydrogen nuclei (protons) precess about the magnetic field lines of a superconducting magnet

• 'gradient' field coils used to scan cross-section

• short radio frequency (RF) pulses cause excitation and change of spin state in successive small regions

• protons excited during the scan emit RF signals as they de-excite

• RF signals detected and the resulting signals are processed by a computer to produce a visual image.

Students will not be asked about the production of magnetic fields used in an MR scanner, or about de-excitation relaxation times.