neuroimaging techniques part 1 & 2 Flashcards
week 2
generally imaging is essential for:
- the localization of a lesion
- determination of a diagnosis
more specifically, neuroimaging iads in ruling in/out
- skull or vertebral fractures
-acute or chronic infarcts (hemorrhage, ischemia) - ## blockages in blood vessels-
xray
non- invasive visualization of internal structures
pros and cons of xray?
pros:
- helpful in detecting presence of fractures, calcified lesions, tumors
cons:
- limited capability to visualize soft tissues
comupted tomography (CT)
- x ray based
- cross sections –> 3D image
pros and cons of CT ?
pros:
- quick
- relatively inexpensive
cons:
- difficult to see posterior fossa and spine due to bone
- exposes patient to radiation
what is the sensitivty and specificity of CT for hemorrhagic stroke ?
good sensitivity
poor specificity
- often need follow up for more info (MRI, angiogram)
CT:
gray matter:
white matter:
air:
fat:
bone:
liquied (CSF,blood)
gray matter: light gray
white matter: dark grey
air: black
fat: dark gray/black
bone: white/light gray
liquied (CSF,blood): very dark/black
CT angiogram
- used to visualize arteries and veins
- used to look for blockages, stenosis, aneurysm or dissection/tearing of walls
- requies injection of contrast material
Magnetic resonance imaging (MRI)
non-invasive method using magnets to produce a 3D image
pros of MRI?
- higher resolution especially for ischemia and areas of soft tissue, posterior fossa, spinal cord
- no radiation exposure
cons of MRI?
- takes time
- pt needs to remain still
- contraindication: pacemaker or metal implants
- expensive
MRI T1 vs T2
gray matter:
white matter:
air:
fat:
bone:
liquid:
T1, T2 respectively
gray matter: dark gray, light gray
white matter: light gray, dark gary
air: black, very dark
fat: white, light/white
bone: white, dark
liquid: black, white
T2 - gray and white are similar to CT, air for both is similar to CT T1 - bone, liquid similar to CT
MRI - fluid attenuated inversion recovery (FLAIR)
- similar to T2 MRI except longer exposure and relaxation time
- CSF signal is attenuated (appears darker)
hemorrhage will be more distinct
MRI diffusion weighted image (DWI)
- MRI technique with contrast added
- used to visuallize areas of ischemia early after loss of blood flow (3 hrs)
DWI = ischemia, early on
MRI - diffusion tensor imaging (DTI)
- MRI technqiue used to map the tracts of axonal white matter in the brain
- often an adjunct to a regular MRI
what does the color coding often denote for MRI - DTI?
denotes the direction the tracts are traveling
- red for Right -left
- blue for dorsal- ventral
- green for anterior- posterior
functional MRI (fMRI) indicates?
- MRI technique that indicates where there is an increase in oxygen uptake compared to the resting state
fMRI shows regions of ___________ neural activity in the brain
increased
what technique is used to visulaize the vascular system?
magnetic resonance angiogram (MRA)
pro of MRA?
cons?
- no radiation or contrast needed
cons:
- increased time and cost
- pt must stay still during procedure
CT or MRI better?
acute head trauma?
CT
CT or MRI better?
lower cost needed
CT
CT or MRI better?
subtle area of tumor, infarct, demyelination, etc.
MRI
