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Chika- SF2 > Neurohistology: Lin > Flashcards

Neurohistology: Lin Flashcards

1
Q

What are the different type of imaging techniques?

A
  • Computed Tomography (CT)–Magnetic resonance imaging (MRI)
  • Intravenous contrast
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2
Q

Role intravenous contrast ???

A

to help differentiate btw different diseases

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3
Q

Hemorrhagic transformation

A

when an ischemic stroke turns in to a hemorhagic stroke

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4
Q

Hydrocephalus

A

this is on the USMLE

-can be communicating or non-communicating

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5
Q

CT

A

computed tomography

  • uses ionization radiation (xray)
  • you have an xray detector and xray source; it spins around and basically takes xray of all the different parts of your body from all the different directions
  • the different tissues in body will attenuate the xray in different amounts (measures attenuation of radiation by tissues)
  • develops initally at EMI (a music company)

RISKS

  • cancer induction (1/10,000)
  • contrast neuropathy (injuring kidneys)
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6
Q

Reading head CT

A

talk about 4 different Head CT densities

  • CSF (dark)
  • grey matter (light grey)
  • white matter (dark grey)
  • Bone (bright
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7
Q

blood on CT

A

looks different depending on how old it is (epidermal hematoma)

  • acute (bright)
  • chronic (dark)
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8
Q

CT with IV contrast

A

-intravenous contrast: iodinated; high attenuation of x-rays; appears bright

-molecule that contain take iodine which attenuate xrays a lot
by doing that you can make the blood vessel look more dense and thus appear brighter

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9
Q

When to use CT WITH IV contrast?

A

since IV and blood are both appear bright you don’t want to use it at any time
DON’T USE for head trauma
-if someone comes in with hematoma (don’t use)
-acute hemorrhage and contrast both appear bright
USE: helpful for intracranial infection or tumor
-it to look for infection or a tumor (enhancement on the CT scan with IV contrast) ie. glioblastoma multiforme
-inflammation from infection and tumor disrupts the blood-brain barrier
-contrast enters into diseased areas of brain and causes them to become brighter and easier to detect

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10
Q

MRI

A

magnetic resonance imaging

  • it uses a huge magnetic field (2,000 times more than the magnetic field of the earth)
  • complex physics; measures radiofrequency signal
  • it aligns the protons in your body in a certain direction, shoot them with the a radio frequency signal and protons start to rotate giving off their own radio frequency field
  • super conductor and chilled in liquid nitrogen
  • it never turns off but you can push a button to quench it
  • MRI uses a strong magnetic field that can turn metal objects into dangerous projectiles (can turn ordinary objects into bullet)

NO XR used so NO CANCER (no known increased cancer risk)

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11
Q

Different sequences in MRI

A

depending on what you’re measuring you can have multiple sequences, here are the four basic:

  • T1 weighted: fat is bright, water is dark (fat has lots of H1s)
  • T2 weighted: water is bright (WW2) water is white
  • diffusion weighted imaging (DWI): measures how fast the water moves in the body in the anatomy; good at looking for acute stroke (decreased density of water molecules)
  • blood is very dark (blood disrupts the magnetic field so you can’t get signals from it
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12
Q

MRI imaging sequencing strengths

A

T1 weighted: good for anatomy and BONE marrow pathology (such as tumor)

T2 good for pathology such as edema (which is all increase water content), infection, tumor, inflammation

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13
Q

Bone is what color in T1?

A
  • bright (white)

- bright fatty bone marrow in skull

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14
Q

susceptibility weighted sequence (SWI)

blood on MRI

A

what disrupts the magnetic field and you cannot get the signal back

-blood on MRI appearance depends on age and composition of blood products

more sensitive than blood in CT???

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15
Q

IV contrast in MRI

A

use gadolinium, large radiofrequency signals

  • disrupts T1 magnetic moment and causes things to appear very bright on the T1 weighted sequences
  • use when interested in infection, inflammation, and tumor because they allow more blood to go into these places
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16
Q

T1 abscess

A

fluid is dark
fat is bright

contrast causes enhancement of the abscess on T1 (remember fluid is dark)

17
Q

Glioblastoma Multiforme CT vs MRI

A

CT: bone bright, scalp fat dark

MRI (T1 weighted): bone is bright (cortical) AND dark (scalp) (why???), scalp fat is bright)

18
Q

Stroke types

A

hemorrhagic stroke: bleeding to brain usually due to HTN or from an ischemic stroke because of tissues dying
ischemic stroke: lack of blodo to brain usually due to clot

19
Q

Acute Ischemic Stroke Timing and pathology

A
  • timing: less than 2 weeks old (including acute and subacute stages)
  • physiology: cytotoxic edema b/c cells are dying; INCREASE amount in INtracellular fluid; DECREASE in EXtracellular fluid
20
Q

Acute Ischemic Stroke CT

A
  • don’t use CT if you think pt has an acute stroke (it takes 6 hours to see a CT abnormality)
  • YOU NEED TO GET AN MRI
  • increased water in brain tissues
  • affected tissue becomes darker with time
  • very early stroke is difficult to detect

-At 24 hours, all patient will have CT abnormality.

21
Q

CT: acute brainstem ischemic stroke

A

bright clot

not reliable finding not all the time

22
Q

diffusion weighted imaging (DWI) cerebellar ischemic stroke

A
  • VERY good for detecting early ischemic stroke (btw 10 and 60 minutes)
  • measures diffusion of water
  • acute ischemic stroke is bright (water is bright)
23
Q

MRI: Acute ischemic stroke (DW)–> What causes the bright signal? What about on the T2 sequence?

A
  • brain cells swell, taking in extracellular water
  • restricted motion of free water outside cells causes the bright signal

T2 weighted

  • increased in water in brain tissue
  • bright signal
  • PRESENT ABOUT 3 hours after the ischemic stroke

how can we tell timine 35mintures????

24
Q

Hemorrhage Transformation

A
  • this is where ischemic stroke becomes a hemorrhaging stroke
  • cells die and you disrupt the BBB and the blood can leak into the brain parenchyma
  • usually occurs 205 days after ischemic stroke onset
  • related to reperfusion of infarcted brain
  • most common cause is treatment with thrombolytic drugs (break clots which cause bleeding)
  • occasionally spontaneous transformations

-usually give thrombolytic drugs for hemorrhaging stroke

acute blood is bright
old blood is dark

we know it is CT scan because bone is BRIGHT

25
Q

Chronic ischemic stroke

A

timing: greater than 2 weeks old
physiology: edema resolved; dead tissue is removed

imaging appearance: dead tissue is replaced by fluid

on CT
-very dark (near water) density
on MRI
-very bright (near water) signal of T2 sequence

greater than 2 weeks old (edema is resolved and dead tissue is removed and have a hole in brain replaced by fluids): fluid is dark on CT; MRI (T2) fluid is bright remember WW2

26
Q

T2 weighted MRI vs CT of old cerebral artery stroke

A

on CT
-bone is very bright; stroke is dark (looks just like the ventricles)

on MRI (T2 weighted) 
-skull is dark; more H2O so more signal (stroke is BRIGHT)
27
Q

Stroke and vessels

A

strokes will look different based on which one of the vessel below are occluded

there are different cerebral arteries that arise in the brain (on CT scan):

  • anterior cerebral artery: chronic stroke in which blood is dark
  • middle cerebral artery: more acute because of all the edema
  • posterior cerebral artery: chronic stroke due to the darker color
28
Q

CT angiogram: arteriogram and venogram

A

looks at vessels; give contrast which creates a cast of the vessels (you can reconstruct them)

-to look at which vessels are affected (the ones that are missing which implies that there is a clot)

29
Q

CT perfusion imaging

A

Howard doesn-t do it
it is at stroke centers

-can use CT to look at the perfusion (blood flow) of the brain

30
Q

Basilar Artery Occlusion (CT)

A

coronal view
-vessels on the posterior circulation vertebral artery to the basilar artery and then you get the posterior vertebral arteries

-darker means more fluid

31
Q

MRI angiogram

A
  • axial view
  • internal carotid arteries
  • anterior cerebral arteries
  • posterior cerebral arteries

we can look for occlusion just like we did in the CT

32
Q

left middle cerebral artery occlusion

A

carotid artery goes to form anterior and posterior cerebellar arteries?????????

33
Q

communicating hydrocephalus

A
  • all ventricles are enlarged

- usually caused by hemorrhage or infection

34
Q

noncommunicating hydrocephalus

A
  • not all the ventricles are enlarged
  • structural CSF flow obstruction
  • causes include brain mass or developmental anomaly
35
Q

communicating hydrocephalus: MRI sagittal T1

A
  • skull is dark
  • fat outside is bright so this is T1 weighted
  • lateral, 3rd, and 4th ventricles are enlarged
36
Q

communicating hydrocephalus: MRI axial T2

A

gigantic lateral ventricle and 3rd and 4th ventricle are enlarged

-ventricles are bright (T2: water is bright) WW2

37
Q

noncommunicating hydrocephalus: large mass in posterior fossa

A

CT because bone is bright

Chika- SF2 (63 decks)

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