MRI Flashcards
What is spin also known as?
angular momentum
What is angular momentum also known as?
spin
What greek letter is this: γ
gamma
What does γ mean in MRI?
gyromagnetic constant
What occurs to the spin of protons when a magnetic field is applied?
The spins will align and spin either up or down in relation to the field
Why aren’t all protons in the low energy alignment when in a magnetic field
thermal energy bounces them between states
How can we change the spin state of protons?
Hit them with a photon that has the right amount of energy to increase them to the higher energy state
What greek letter is this: ω
omega
What does ω mean in MRI?
Larmor frequency
What is the symbol for the Larmor Frequency
ω
What is the Larmor frequency
rate of precession of the magnetic moment of the proton around the external magnetic field. The frequency of precession is related to the strength of the magnetic field,
What is the Larmour equation?
ω = γB
B is magnetic field strength
What’s the name of the distribution of proton energy levels due to thermodynamics in nuclear resonance?
The Boltzmann distribution
FID acronym in MRI?
Free induction decay
What’s it called when protons are precessing in synchronicity?
phase coherence
What is Free Induction Decay in MRI
How quickly the signal of the precessing protons decreases after ceasing the radiofrequency burst
What is T2 known as?
transverse relaxation rate
spin-spin relaxation rate
What is T1 also known as?
longitudinal relaxation rate
spin-lattice relaxation rate
What is the relation of Free Induction Decay and T2?
FID is made up of the T2 relaxation rate and T2 star
What is T2 STAR?
The component of FID not due to true T2 relaxation, but due to phase incoherence of the protons
What is the infomartion that needs to be known about each cos/ sine wave that makes up an image in MRI?
spatial frequency
magnitude
orientation
phase
are the higher or lower frequency waves represented near the middle of k-space?
lower frequency (longer waves)
In what order do the gradient encodings occur in MRI acquisition?
slice selection
phase encoding
frequency encoding
When does slice selection encoding occur in MRI encoding?
at the same time as the RF pulses are initially emitted
When does phase encoding occur in MRI encoding?
between the 2 different bursts of RF emissions (after 90 degree flip but before 180 degree flip)
When does frequency encoding occur in MRI encoding?
during the acquisition portion, when the echo is being re-emitted by different parts
