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28 Cards in this Set
- Front
- Back
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Nervous System- Neuroradiology by Benseler
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Nervous System- Neuroradiology by Benseler
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Advantages of CT...excellent for what? Better than MRI for what?
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Quick (5 minutes)
Readily available Less expensive than MRI MR may require pre-approval/ CT quick access **Excellent for acute intracranial hemorrhage **Better than MR for skull fracture |
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When looking for a midline shift in the brain, you look for a midline shift from which structure?
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septum pellucidum.
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Can CT measure density of tissue? If so, then what are some measurements?
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Can measure specific CT density of tissues
Hounsefield Units 0 = water density + 1000 = bone 1000 = air + 60 – +80 = blood - 5 to –12 = fat |
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Magnetic Resonance Imaging... how do they work?
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The body contains billions of hydrogen atoms
Hydrogen atoms may simply be composed of a proton (H+) This small + charge represents a tiny magnet with N and S poles Each proton is a tiny magnetic vector MRI uses hydrogen ions; Hydrogen ions are also called protons; These represent tiny magnetic vectors Proton magnetic vectors are in random alignment in the body Placed in a strong magnet, these tiny magnetic vectors align The experiment: Tip the vector off axis using an RF (radio frequency) pulse Images are created by the energy released as the vector returns to steady state alignment |
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MRI Sequences, T1 vs T2
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T1 = the “anatomic” sequence
T2 = the “pathology” sequence PD (proton density) = between T1 and T2 (character of both) On T1 water is dark black (no signal) On T2 water is bright white |
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What is FLAIR Sequence?
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IR = inversion recovery, a way to look at the protons of the body that shows great pathology of the brain
- anything that is normal free-flowing fluid will not have signal (black), but anything pathological will be white |
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Trick to differentiate MRI from CT Scan.
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if you look at an image and you follow the brain out as far as you can, and if the structure adjacent to the brain is black, that's an MRI. If it's bright white, it's a CT Scan.
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What 3 things on MRI look black?
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cortical bone
air flowing blood |
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MRI is excellent for ____ matter
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white
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Advantages of MRI
what is it good for assessing? What can it detect earlier than CT? |
**No bone artifact (a problem for CT especially in the posterior fossa)
**Better assessment of tumors, white matter disease and early edema **Can detect ischemic injury 24-36 hours earlier than CT Detects presence of vascular flow Multi-planar capability |
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Disadvantages of MR
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No metal on patient
No pacemakers No ferric aneurysm clips Claustrophobia Expensive, needs insurance pre-approval |
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A 26 y/o patient presents to the ED after being struck by a softball bat. You want to rule our intracranial hemorrhage. You order:
A. CT B. MRI |
CT
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Which modality is best for evaluating white matter disease?
A. CT B. MRI |
MRI
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Contrast use to do what?
what are the contrasts called for MRI and CT? |
Used to:
-Enhance tumors -Inflammatory processes -Enhance vasculature and vascular lesions MRI: gadolinium (alters the magnetic properties of certain materials) CT: iodinated contrast Gadolinium occasional serious skin reactions |
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Head Trauma
Become familiar with intracranial hemorrhage including: Epidural hematoma Subdural hematoma Parenchymal contusion Shear injuries |
ok.
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Epidural hematoma, what does it look like?
where does it happen most often? what is it ass'd with? what is the shape that we see? |
A traumatic extracerebral blood accumulation
Occurs in the potential space between the skull and tightly adhered dura 90 % arterial 10% venous 85-95% association with skull fracture Bleeding comes from meningeal arteries 66% middle meningeal artery looks like wallpaper stripped Arterial bleed under pressure strips dura from the inner table of the skull Epidural hematoma = biconvex shape -Firm adherence of the dura at the hematoma margins -Strong dura attachment at cranial sutures -High pressure arterial bleeding |
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Epidural Hematoma:
Clinical Presentation Treatment Children |
Variable and non-specific
1/3 of the time “classic” lucid interval If confined to epidural space, may remain conscious If associated intracerebral or intra-dural bleeding, most lose consciousness 9 % of EDH increase in size after the initial CT If small, non-operative treatment If temporal, may produce pressure on the brain stem – more likely operative In children, skull fracture may not be seen (elasticity of bone) |
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Subdural Hematoma: where's it at. what's bleeding? why's it happening?
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Subdural: a potential space between the dura and the meninges covering the brain (arachnoid and pia)
Cerebral cortical veins are invested into the meninges closely associated with the surface of the brain Venous bleeding Tearing of bridging cortical veins Occurs during acceleration – deceleration injuries Results because of difference in inertia of the skull vs. the brain & cortical veins |
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Falls vs MVAs... which is more common for which?
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SDH more common with falls
EDH more common with MVA |
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SDH. who gets them, what is the shape? how big of an area does it cover?
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SDH more common in older patients, alcoholics
SDH’s are crescent-shaped Spread over a larger area, limited by the falx and the tentorium |
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CT density with SDH:
Acute Subacute Chronic |
CT density with SDH:
Acute 0 to 3-4 days hyperdense (bright white) Subacute 3 to 20 days isodense (looks like brain) Chronic > 20 days hypodense (darker) |
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Shear Injuries...
how do they happen? what does it usually involve? where does it happen? |
Occur with rapid acceleration/deceleration
Usually involves large WM tracts: corpus callosum, brainstem and deep white matter Occurs at gray-white matter interface due to slight differences in mass Minor differences in tissue inertia |
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Ischemic Infarction shape and contents
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Left Middle Cerebral Artery Infarction with midline shift:
Most useful landmark for measuring midline shift: Septum Pellucidum Edema affects the white and gray matter This type of edema is called **cytotoxic edema (stroke) edema in the brain with wedge shape involve white and gray matter wider peripherally than centrally |
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Previous bilateral “frontal lobotomy”
why do this. |
Previous bilateral “frontal lobotomy”
Note the low density changes in the frontal lobes These are areas of old injury called **encephalomalacia This patient was not symtomatic treatment for depression |
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hemorrhage or tumor
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acute hemorrhage is bright white.
lens shape. tumor edema is confined to white matter (aka vasogenic edema) |
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____ is 1st in the emergent setting to rule out hemorrhage.
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CT
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____ is more sensitive for edema, tumors, infections and white matter disease.
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MRI
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