MRI Flashcards
Spin
A quantum mechanical property of protons
- two values: parallel or antiparallel
Precession
The change in the orientation of the rotational axis of a rotating photon
B0
An external static magnetic field
- it aligns more proton spins parallel to the magnetic field
- this creates a net magnetisation (M) in the z direction
What does the electrical coil do in MRI
It generates radio frequency magnetic waves. This excites the protons, causing them to flip their spins to antiparallel.
What does the reception coil do?
Often the same coil as the electrical coil, it detects the radio frequency magnetic field energy produced by photons once the electrical pulls stops and the spins relax.
T1 relaxation time
depends on the net direction of spins
T2 relaxation time
depends on the net coherence of precessions
What enhances T1 weighted images maximally?
Short repetition time (TR) and short echo time (TE)
What enhances T2 weighted images maximally
Long repetition time (TR) and long echo time (TE)
What does a T1 weighted image look like?
Gray Matter = Grey
White Matter = White
What does a T2 weighted image look like?
Gray Matter = White
White Matter = Grey
What are T1 weighted images useful for?
Identifying anatomy
What are T2 weighted images useful for?
Detecting pathology
