Flashcards in Neuroimaging Deck (20):
-when not otherwise getting a CT scan & suspect skull fx, sinusitis, facial bone tumors, nose pathology, foreign body
-eval for fx of mandible and maxilla
-eval of skull for lytic lesions such as in Multiple Myeloma
-looking for scalp full thickness laceration or boggy hematoma
-eval for foreign body such as glass
-unable to see fx in skull base, if basilar skull fx
-cannot evaluate intracranial contents
-what is commonly missed on CT?
-evaluate skull, skull base, vertebrae
-eval ventricles (hydrocephalus, shunt placement)
-suspicion of intracranial masses, mass effect
-looking for acute hemorrhage, ischemia
Tumors are commonly missed on CT
If patient is acutely ill, needs LP, and youre not sure if they have increased ICP you get what type of scan? Why?
When patient comes into ER with stroke like symptoms what test do we get? why?
You get CT scan, looking for things that would increase ICP such as mass. If there is increased ICP you might see midline shift, then you CANNOT get LP, this will cause brain herniation and death.
Pt coming into ER needs immediate CT scan, this is used to R/O hemorrhagic stroke. It cannot tell us acutely if the pt is having an ischemic stroke.
-Circumstances in which you would use contrast? no contrast?
- neoplasm, infection, vascular dz, inflamm dz
-trauma, R/O stroke, hemorrhagae, hydrocephalus, dementia, epilepsy, congenital malformation
When interpreting CT scan of the Head what 4 things should we be looking for?
-look at each side and compare
CTs have two different technniques for evaluation, what are they?
Brain window for looking at soft tissue
Bone window for looking at bone.
WHat appears bright or dark on CT?
Bright: the more dense the tissue, any calcified structures (bone), new hemorrhage
Dark: water or CSF
Explain the three types of Hemorrhages of the brain
Subarachnoid Hemorrhage: arterial bleeding on the surface of the brain, between pia mater and arachnoid mater.
*usually from the circle of WIllis*
SUbdural Hematoma: venous bleeding between arachnoid and dura
Epidural Hematoma: dural artery or venous sinus bleeding between skull and dura; associated with skull fx
Causes of :
Subarachnoid: trauma, ruptured cerebral aneurysm
Subdural: tearing of bridging veins from deceleration, acceleration, or rotational forces (ex. elderly fall)
-epidural: associated with skull fx, fx bone lacerates a dural artery or venous sinus (high velocity trauma)
Describe what each of the following look like on CT
Subarachnoid: high density blood fills the sulci
Subdural: crescent shaped, midline shift
-the longer the blood has been sitting there the darker its appearance.
Epidural: biconvex mass, bleeding into the brain and soft tissue
Presentation of each:
Subarachnoid: acute, thunderclap HA
Subdural: may be insidious, worsening HA over days
Epidural: acute presentation
Indications for CT angiography?
Vascular dissection of carotids
Evaluation of carotids
- Whats the difference between T1 and T2 weighted images?
-what bright/dark on T1? T2?
T1 looks at normal brain anatomy, T2 looks at abnormal processes in the brain
-Bright= fat, white matter
-Bright= water, blood
-Dark: white matter
Indications for MRI
-subacute and chronic hemorrhages
-cerebral infarcts (Stroke, not acute; get the day after)
-primary and metastatic brain tumors
-multiple sclerosis and other demyelinating dz
-new onset or refractory seizures
MRI is superior to CT in every pathology except for?
except for skull fx and acute subarachnoid hemorrhage (b/c its slower than CT and costs more)
What are the advantages/disadvantages of CT/MRI?
Advantage of CT:
-simple, cheap, fast
-tolerated by claustrophobes
-no absolute CI
-better than MRI for bone detail
Disadvantages of CT:
-IV contrast complication
Advantage MRI :
-much broader palette of tissue contrasts
-no ionizing radiation
-IV contrast better tolerated
-better for tumor evaluation
-difficult for unstable patients
-several absolute CI (cardiac pacemaker, aneurysm clips)
-claustrophobes need sedation
-image interpretation more challenging
-lacks bone detail
What is MR Angiography used for?
Useful for evaluation of intracerebral vessels
Cerebral Angiography (CT)
-gold standard imaging for what?
gold standard for imaging the carotid arteries and evaluating cerebral aneurysms after subarachnoid hemorrhage.
-Intraarterial tx of verebral vasospasm