Investigations
CT and MRI Imaging
· CT:
o Looks for density Þ bones are white (hyper-dense), air is black
o If it is contrast enhanced then vessels will appear whitish
·
MRI (=Magnetic Resonance
Imaging):
o Looks for H atoms
o Very strong magnet lines up H atoms (effectively little dipoles), radio
waves emitted which disturb net magnetic vector, then measure radio frequency
emitted by atoms as they return to aligned state
o Describe as hypo or hyper intense
– as relates to signal intensity not density
o Bones on both are black (no free fluid)
o T1 weighting: simple fluid black (eg CSF, urine). Shows exquisite anatomy
o T2 weighting: simple fluid turns white. Shows pathology, due to tissue
hydration (eg infection, tumour). T2
shows H2O. Flowing blood is black
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