What Can MRI Do for You?. Noninvasive imaging cellular /macromolecular contents molecular magnetism transport processes. Yi Wang. Transport processes. This category of MRI contrast mechanisms is useful for assessing live tissue functions: Flow Perfusion, convection, permeability
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This category of MRI contrast mechanisms is useful for assessing live tissue functions:
Diffusion increase in tumor (bright)
Diffusion decrease in acute ischemia (dark)
Reduced perfusion (yellow)
Flow (vessel blocked in left)
This category of MRI contrast mechanisms is useful to assess molecular properties and their changes in metabolism (oxygen metabolism, iron metabolism):
An external magnetic field puts force/torque on electrons.
Protons are too heavy to respond.
Unpaired e- Spin response (torque):
Magnetic moment parallel to B
Orbital response (Lorentz force):
Magnetic moment opposing B
Chemical shift at nucleus
This category of contrast mechanism is useful to examine macromolecular/cellular contents in water.
T2 long, 2 sec
Lots of contents
T2 short, 75 msec
T2 median, 200 msec