CNS imaging Flashcards
what is tissue appearance in CT (dark to light)
air, fat, soft tissue, water, bone, metal
what is mutlidetector CT
allows volume to be scanned at a time
adv of multidetector
fast - can capture physio
allows reconstruciton
adv of CT
- fast
- available eerwhere
- can scan mutli parts
2 ways contrast can be injected
- intravenous
2. intrathecal
2 dis of CT
- radiation
2. contrast can cause renal dysfunction
what are 2 types of CT windowing
- soft tissue
2. bone
what are diffs in hounsfield units between 2 types
bone - large diff.
tissue - only a few
2 good uses of CT
- bone
2. blood
why is CT good for blood
high attenuation, good for acute sits.- can localize
what is epidural hematoma
blood leak into dural space after menigeal artery break - good at first and then deteriorate
characterisitics of epi hematoma
lentile shape, slow onset
what does acute subdural look like on CT
high density region
what does subacute look like
almost isodense
what does chronic look like
hypodense compared to parenchyma
what is cerebral contusion
brain hitting skull
2 types of cerebral contusion
- coup - direct hit
2. contre-coup - bounce back to the other side
test for spine fracture?
CT - fast and large areas
what is MRI measure of (3)
- number of protons in voxel
- T1 of tissue
- T2 of tissue
what is T1 relaxation
spin-lattice - relies on longitudinal relaxation
what shows on T1 (2)
fat - white
fluid - dark
what is T2 relaxation
spin-spin - relies on transverse relaxation
what shows on T2 (2)
fat - intermdiate bright
fluid - bright
what are 3 basic flavors of pulse sequences
- T1 - dark CSF
- PD weighted - CSF and everything is grey
- T2 - CSF is white
what is key to galolinium enhanced MRI
doesn’t cross BBB
how do most pathologies appear on T1 and 2 and exceptions
T1 - dark (fat, melanin, calcium, protein)
T2 - bright (late blood, calcium, air)
what is FLAIR imaging
nullifies signal from CSF so can see things near CSF interface
what to look for in MS
- plaques that are most common in white matter
- hyperintense in T2
what are stages of Hb over time
oxy>deoxy>met>hemosiderin
how does this blood show up on MRI
oxy and deoxy - not well > CT
met - bright on T1-2
hemo - dark on T1-2
what is used for imaging hemmorage
gradient echo (GRE) and succepitibitlit weighted (SWI)
what does GRE show
artifact from microhemmorages
what 3 things does imaging method in stroke depend on
- timing
- ongoing Sx
- transient Sx
why is imaging acute stroke important
can be treated
what are 2 treatments for acute stroke
- intravenous tPA (clot-buster)
2. embolectomy
what is needed in assessment of acute stroke(2)
- is strke present
2. rule out contraindications (hemmoarage or completed)
what is best imaging of acute stroke
CT without contrast
3 CT signs of acute stroke
- loss of cortex/grey matter
- swelling/loss of sulci
- hyperdense MCA sign
when is MRI used in stroke
- subacute - takes too long for acut
- stroke too small for CT
- in areas that can’t be seen in CT (post. fossa)
what does stroke look like in MRI
hyperdense on T2 and FLAIR
what is diffusion weighted imaging
water in stroke can’t move out of cell - shows as white
what is ADC map and what will stroke look like
addition of all the images - stroke will appear dark
when is DWI used
in firt 7-10 days, after that the cells break down and water can come out
3 adv of MRI
- no radiation
- good visualization of brain and cord
- can use methods to ID pathologies
3 methods to image vasculature
- ultrasound
- CT angio
- MRI angio
what is hypo to hyperechoic on ultrasound
air>fluid>tissue>fibrous tissue>bone
when is ultrasound used
in neck - can’t penetrate bone
what is endovascular treatment
put in coils to block off aneurisms
