11 - NEURORADIOLOGY Flashcards
1
Q
Axial noncontrast CT images of the brain
A
2
Q
Sagittal and coronal
postcontrast CT of
the brain
A
3
Q
Axial Diffusion Weighted MRI
sequence of the brain
A
4
Q
Sagittal T1-weighted MRI sequence of the brain
A
5
Q
Sagittal T1, T2, STIR-weighted MRI
sequence of the lumbar spine
A
6
Q
Axial T2, T1-weighted MRI
sequence of the lumbar spine
A
7
Q
CT Angiogram (CTA) of the head and neck
A
8
Q
MR Angiogram (MRA) of the head without contrast
A
9
Q
3D reconstructions of MR Angiogram (MRA) of the head & neck
A
10
Q
Diffusion Tensor Imaging (DTI) of the brain white matter tracts
A
11
Q
MRI Spectroscopy of the brain
A
12
Q
Direct catheter cerebral angiography
A
13
Q
Left posterior cerebral artery (PCA) occlusion status post thrombectomy
A
14
Q
Right middle cerebral artery (MCA) occlusion status post thrombectomy
A
15
Q
A
16
Q
CT guided bone biopsy of a lytic vertebral body lesion
A
17
Q
ACR APPROPRIATENESS CRITERIA: Sudden, severe headache or “worst headache of life”. Initial imaging.
A
18
Q
ACR APPROPRIATENESS CRITERIA: Traumatic visual defect. Suspect orbital injury. Initial imaging.
A
19
Q
ACR APPROPRIATENESS CRITERIA: Suspected optic neuritis. Intial imaging.
A
20
Q
strokes - neuroradiology
A
- The goal of imaging in a patient with acute stroke is:
-Exclude hemorrhage
-Differentiate between irreversibly affected brain tissue and reversibly impaired tissue (dead tissue versus tissue at risk)
-Identify stenosis or occlusion of major extra- and intracranial arteries - In this way, we can select patients who are candidates for thrombolytic therapy.
21
Q
CT for strokes
A
- CT has the advantage of being available 24 hours a day and is the gold standard for identifying hemorrhage.
- On CT 60% of infarcts are seen within 3-6 hrs and virtually all are seen in 24 hours.
- The overall sensitivity of CT to diagnose stroke is 64% and the specificity is 85%.
- MRI is far more sensitive in diagnosing acute strokes compared to CT
22
Q
CT EARLY SIGNS OF ISCHEMIA
A
- Hypodense brain tissue, loss of GW differentiation
- Obscuration of the BG, esp the lentiform nucleus
- Dense MCA sign
- Insular ribbon sign
- Sulcal effacement
22
Q
NORMAL CT HEAD
A
23
Q
EARLY SIGNS OF ISCHEMIA
A
24
Why do we see ischemia on CT?
25
HEMORRHAGIC INFARCTS
26
CTA AND CT PERFUSION
* Once you have diagnosed the infarction, you want to know which vessel is involved by performing a CTA.
27
CTA SHOWING ABRUPT OCCLUSION OF THE RIGHT MCA
28
MRI DIFFUSION WEIGHTED IMAGING SHOWING AN ACUTE RIGHT MCA VASCULAR DISTRIBUTION INFARCT
29
CT PERFUSION
* With CT and MR-diffusion we can get a good impression of the area that is infarcted, but we cannot assess for an **ischemic penumbra** (tissue at risk).
* With **perfusion** studies we monitor the first pass of an iodinated contrast agent bolus through the
cerebral vasculature.
* **CT Perfusion** will tell us which area is at risk.
30
MISMATCH
**CBV (Cerebral Blood Volume):**
CBV refers to the total volume of blood in the cerebral vasculature at a given time.
It represents the amount of blood within the brain's blood vessels.
**CBF (Cerebral Blood Flow):**
CBF refers to the rate of blood flow through the cerebral vasculature per unit of time.
It represents the amount of blood flowing to the brain tissue.
**MTT (Mean Transit Time):**
MTT is a parameter used in imaging studies (like perfusion imaging).
It represents the average time it takes for blood to travel from the arterial input to the venous output.
Now, let's address the scenarios:
**Ischemia (2/2 Autoregulation):**
In ischemia, when autoregulation is still effective (maintaining CBF despite changes in perfusion pressure), you might observe:
**High MTT:** Blood takes longer to transit through the brain.
**Low CBF:** Despite the prolonged transit time, the overall blood flow is reduced.
**Normal CBV:** The total volume of blood within the vasculature may remain relatively constant.
**Infarct (Autoregulation Fails):**
In the case of infarction where autoregulation fails, you might observe:
**Low CBV:** The total volume of blood within the vasculature decreases.
**Low CBF:** The rate of blood flow to the brain tissue is reduced.
These changes occur as a result of compromised blood supply to the affected area.
31
MRI (T2, FLAIR, DWI) - Stroke
31
A 64-year-old man presenting with
headache and acute aphasia.
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DWI
* DWI is the most sensitive sequence for stroke imaging and earliest to turn positive.
* DWI is sensitive to restriction of Brownian motion of extracellular water due to imbalance caused by cytotoxic edema. (vs vasogenic edema associated with tumors)
* High intensity on DWI indicates restriction of the ability of water protons to diffuse extracellularly.
* Acute infarct is DWI bright and ADC dark
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INTRACRANIAL HEMORRHAGE
* Categorize by location
* CT first imaging modality used to assess pts with suspected ICH
* Bright is blood
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EPIDURAL HEMORRHAGE
35
Epidural hemorrhages - Noncontrast CT of the head
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SUBDURAL HEMORRHAGE
* Between dura and arachnoid mater (outermost and middle layer of 3 meninges)
* Etiology varies:
-Infants- non-accidental injury
-Young adults- MVA
-Elderly- falls
* Acute SDH usually 2/2 trauma
* Tearing of bridging cortical veins as cross subduralspace to drain into dural sinus
* Crescent shaped, not limited by sutures, limited by falx/tentorium
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subdural hemorrhage - non contrast CT of the head
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SUBARACHNOID HEMORRHAGE
* Within the subarachnoid space- sulci or basal cisterns
* Usually present with **thunderclap headache**, **worst of their life**, **photophobia**
* Causes include:
-Trauma
-Spontaneous- ruptured aneurysm, AVM, cerebral amyloid angiopathy, ruptured mycotic aneurysm, RCVS/CNS vasculitis, cocaine use, anticoagulation therapy
39
SUBARACHNOID HEMORRHAGE - noncontrast CT of the head
40
Intraventricular hemorrhage - non contrast CT
41
Intraparenchymal hemorrhage - non contrast CT
