Neurologic Diagnostic Imaging Flashcards
the use of CT Scans in Neurologic Diagnosis
how CT works and colors
indications
contraindcations
CT = rotating scanner of xray imaging taken from multiple angles and creates cross sectional views of the body
- shades of black, grey and white depend on density
- denser objects: less xrays pass through = appears white, where air, freely pass = black
Hyper/hypodense are terms used in CT to dscribed strcutres in the greyscale
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unenhanced CT brain is the preferred inital screening technique for acute and hyperacute pathologies of the brain
- they focus on looking for blood or looking for mass effect shift
- most sensitive at picing up bone and calcification on imaging over the MRI
Indications (anything looking for blood or bone)
- acute head injury
- suspected hemorrhage
- skull fractures
Contraindications
- pregnant (not absloute)
- special considerations for pediatric scans (due to increased radiaion and risk of CA)
use of the bone window on CT for head imaging
the “Bone WIndow” is a set of CT hounsfiedl units which directly hyperfixate on the bone in the images
allows bone to be hyperdense on imaging
- easily identiy fractures of the skull & see concominante inflmmation and swelling (less detailed)
the use of MRI for brain imaging
- study of choice for what
- advantages to CT for waht
- contraindicated in
MRI: study of choice for non-acute pathologies of the brain
- detecting and staging intracranial and spinal cord abnormalities
- demyleinating disease
- crainial nerve dysfunction
- neurodegenerative disease
- encephalitis and stroke (after head CT)
Postives
- more senstive for soft tissue pathology
- see the posterior brain better
- angiographic images can be added without the use of contrast
NEgatives
- requires long scan time and still
Contraindications
- those with pacemaker
- metal impacnts
- spinal cord stimultors
- metallic FB (GSW)
How does an MRI work
- T1 and T2
- T2 FLAIR
MRI: uses non-ionizing radiation microwaves
- the images are created based on the ability of the waves to be absorbed and emitted at different wavelengths into images
terms used: hypo or hyperINTENSE
T1 = anatomic images = CSF will be BLACK in this scan
- subcut. = white
- grey matter = appears hypointense relative to the white matter
T2 = pathologic image = CSF will appear WHITE in this scan
- subacut. = black
- most pathologies with increased fluid in the tissue will show up as high signal white - indicating edema
T2 FLAIR = (fluid attenuation inversion recovery) T2 image wihtout CSF brightness
- this is the BEST study for edema
T1 with contrast: T1 = black CSF, but the tumors will appear bright “Tumor Image: white because vascualrized
Imaging Indication by abnormality
acute stroke
HA, acute & severe
HA, chronic
seizure
blood
head trauma
extracaroid disease
hydrocephalus
masses
change in mental status
Acute Stroke = head CT (then followed with MRI)
HA, acure & severe = HeadCT noncontrast (SAH)
HA, chronic = MRI without and with contrast
Seizure = head CT (followed by MRI without and with contrast)
Blood = CT noncontrast
head trauma = noncontrast CT
extracaranial carotid disease = doppler US
Hydrocephalus = MRI
Vertigo = MRI contrast
Masses = Contrast MRI
change in MS = Head CT (then MRI with and without contrast)
Myelopgraphy
- how is it done
- what is it used for
- what type of pt.
Myleography
- under floroscopic guidance, dye injected into thecal sac (dura mater surrouding cauda equina and cord)
- then, under xray or CT the spinal cord is evaluated, along with spinal nerves and the linging
this is used in those who cannot undergo MRI
used to detect…
- compression of the nerve roots due to herniated disc
- depcition of Spinal Stenosis
- spinal tumor
- infection
- spinal lesions
Angiography
when is it used
what is it
Angiography
- xray/CT/MRI with dye injected into the vasculature
evaluates
- anyuresums
- blockages
- clots
- injury
- vascular malformations
- vessel rupture or tear
what does it look at
- the vesesel of head, brain, neck, heart chest, plevis and extremities
the injection of dye is timed so that it will highlight specific locations thorugh the arterial or venous phases
dye directly into the vessels
CT Angiogram of head
- gives accurate details of major brain vessels after a bolus dose of IV contrast
- vasculitis, vasospams, clot, etc.
- most commonly for anyuresums
wathc nephrotoxicity with dye!!
Epidural Hematoma
an epidural bleed between the dura mater and the skull
will appear like a football shape on CT imaging
commonly due to..
- blunt force trauma (baseball) to the temporal/parietal areas
- usually an acommpaying skull fracture
- bleeding of the middle meningeal artery
CT Findings
- high density biconvex area of enhancement
- will NOT cross suture lines, and will be in the temporal area
Subdural Hematoma
a bleed of bridging vessels between the dura and the arachnoid space
commonly due to a acceleration-decceleration injury
CT appearance
- hyperdense (white) area of cresent-formation
- this WILL cross suture lines
- creasant shape
Subarachnoid Hemorrhage/Anyuresum
a bleed between the subarachnoid spcae and leakage into the sulci/fissures of the brain and CSF
CT findings
- hyperdense blood iwthin the fissures of the braine and within the basal cisterns
- “start of death”
the use of cerebral angiography with a SAH
once the diagnosis of a subarachnoid hemorrahge has been made on CT – there needs to be location of the anyuresum that is causing the bleed
often times this can be doen with cerebral angiogram but,
conventional catheter anigographty or digital subtraction anigograhy are the gold standards for vasucalr evaluation
but often times, ct anigo (with just administering the fye and timed photos) is done as its.
- noninvasive
- good for anyuresums > 3 mm
use of imaging for a CVA
CVA: ischemic stroke
CT is often performed first
most commonly, findings are negative on CT for the first 24 hours
thus, MRI is superior, but CT should still be done first mainly to R/O bleed
if its been 12-24 hours since onset: there could be low areas of attenuation in vasculature formation
if its been > 24 hours since: you can probaly see better lesion with mass effect
peaking at 3-5 days
HOWEVER< diffusion weighted imaiging CT is the most sensitive for stroke imaging in sequence
use of diffusion weighted imaging & strokes
diffusion weighed imaigng is the most senstive sequence for stroke imaging
DWI: follows the changes of movement of water through tissues and uses the contrast changes
- free diffusion of protons occurs only when the cell membrane is LOST
- thus when the integratiy is lost (dead) you get more free flowing of the water through these areas, thus appearing brighter in imaging
Hydrocephalus and the imaging techniques for best
hydrocephalus
- the expansion of the ventricualr system due to increased volume of CSF within the ventricles
due to
- under abosrbtion
- reduced outflow
- overproduction
Imaing findings : CT
- see enlarged ventricles (temporal horns) with normal or flattened sulci
how will cerebral atrophy look on CT and who may have this
Cerebral Atrophy
- alcoholics
- AD
CT imaging
- diffused cortical atrophy
- lost grey and white matter
