Steps to Create fMRI
Description
Gradient Echo Sequence
Description
Two Basic Pulse Sequences
T2 vs T2*
T2*
What it is and how its measured
Magnetic Properties of Hemoglobin and Deoxyhemoglobin
How these are exploited in fMRI
Oxygen Demand
depending on what part of brain is being used the most, there is more oxygen in that are aof the brain
fMRIs
Hemoglobin
Transports oxygen 
Four subunits: 
  • each pocket has iron containing hem groups, and oxygen binds to the proteins.
  • Oxygen cannot be transported by itself, hemoglobin helps carry oxygen
fMRI
Everything the device exploits is located INSIDE the body "endogenous" -  hmoglobin
d
Description
Oxygen Binded changes Properties
  • Dimagnetic material (repels the magnetic field) - when oxygen is bound
  • Paramagnetic material (slight attraction to magnetic field) - when oxygen is not bound
  • ferromagnetic material (Strongly attracted, bends the field a lot
Magnetic Properties
  • Dexoy-hemoglobin has a smaller T2 star, decays signal faster than T2
  • Oxy-hemoglobin has an almost equal T2* to T2
  • Make an MRI image where image brightness is related to T2*
  • Image relative ratios of oxy- and deoxyhemoglobin (image oxygen utilization)
180 degree pulse is applied
Because the magnet is not perfect! 
Apply gradient field here only because we need to find location
T2* has Inverse Gradient
No 180 degree pulse like the T2
Note
if you get the contrast between deoxy and oxy whats the point of doing an inverse gradient as opposed to a 180 degree pulse
   Login to remove ads X
Feedback | How-To