Diamagnetic -weak susceptibility: tissue, OxyHb...
Paramagnetic - stronger susceptibility: Gd,DeOxyHb,MetHb
Superparamagnetic - iron oxide, ferritin, hemosiderin
Ferromagnetic -iron,nickel, cobolt -----large distortions in image in plane& through plane. Also affecting sat bands
Mitigation: Spin echo instead of gradient echo - the 180 refocusing pulse of SE after the 90 pulse makes the difference.
After the 90 pulse some protons will be faster because of inhomogeneity, when they are flipped all the way over (still in x-y plane) the will now be the last.
Readout is done after these hace caught up.
TSE is ok, use short echo spacing and longer echo trains
Increase bandwidth/pixel (ex use 440/pixel)
increase matrix
use thinner slices
use stir instead of chess for fat suppression
dont use paralell imaging
dont use homogeneity correction
london implant retrieval center