CT and MRI Imaging - Patient Investigations

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