Explain briefly the main principles of the use of magnetic resonance to obtain diagnostic information about internal body structures.

Question 15

Explain briefly the main principles of the use of magnetic resonance to obtain diagnostic information about internal body structures. [8]

Reference: Past Exam Paper – June 2011 Paper 42 & 43 Q10

Solution:

A strong / large (uniform) magnetic field is applied which causes the nuclei to precess / rotate about the field direction.

A (r.f) radio frequency pulse is applied at the Larmor frequency which causes resonance / nuclei absorb energy.

On relaxation / de-excitation, the nuclei emit r.f pulse which is detected and processed.     

Superimposing a non-uniform field on the uniform field allows the position of the resonating nuclei to be determined and for the location of detection to be changed.