Neuroimaging Flashcards
1
Q
Neuroimaging Modalities
A
- Plain radiographs
- Ultrasound***
- Computed Tomography (CT)
- Magnetic Resonance Imaging (MRI)***
- Nuclear Medicine (Scintigraphy)
- Positron Emission Tomography (PET)
- Myelography
- Angiography
*** No ionizing radiation used
2
Q
Plain Radiographs
A
-
Advantages
- Readily available in all hospitals
- Easily obtained and relatively inexpensive
- Portable
- Provides details of the osseous structures
-
Disadvantages
- Not good for brain parenchyma
- Does not demonstrate the underlying brain
- Uses ionizing radiation
3
Q
Computed Tomography (CT)
Advantages vs Disadvantages
A
-
Advantages
- Non-invasive
- Readily available 24/7
- Rapid scan time – < 5 seconds
- Provides basic anatomic detail
- Images can be reformatted into multiple planes
- Allows for total body scanning
- Not limited by ferrous materials
-
Disadvantages
- Ionizing radiation
- Not (usually) portable
- Portable CT available in some institutions
- Poor quality images
- Posterior fossa images degraded by artifact from temporal bone
- Iodinated intravenous contrast has limitations in those with allergies, asthma, renal failure
4
Q
Computed Tomography (CT)
Imaging Planes
A
3 planes ⇒ coronal, sagittal, and axial
5
Q
Normal Brain Anatomy
A
- Cerebrum
- Frontal lobe
- Parietal lobe
- Occipital lobe
- Temporal lobe
- Cerebellum
Differentiate from white matter (darker on CT) vs. gray matter.
6
Q
Ventricular System
A
-
Two lateral ventricles
- Each has a body and multiple horns:
- Frontal (anterior)
- Temporal (inferior)
- Occipital (posterior)
- Foramena of Monro
- Each has a body and multiple horns:
-
Third ventricle ⇒ Midline structure
- Cerebral aqueduct of Sylvius
-
Fourth ventricle ⇒ Located in the midline posterior fossa
-
Foramena of Luschka** and **Magendie to basal cistern
- Luschka ⇒ Lateral
- Magendie ⇒ Medial
-
Foramena of Luschka** and **Magendie to basal cistern
7
Q
Extracerebral Spaces
A
-
Epidural (extradural) space ⇒ potential space bound by sutures
- Blood in epidural space cannot cross suture lines
-
Subdural space ⇒ potential space bound by interhemispheric fissure/tentorium
- Blood in Subdural space cannot cross midline
-
Subarachnoid space/compartment ⇒ contains CSF and bridging veins
- Blood cannot cross midline, contains veins
8
Q
Vascular Structures
A
- Arteries ⇒ Circle of Willis
-
Anterior circulation
- Internal carotid arteries
- Anterior cerebral arteries (and anterior communicating artery)
- Middle cerebral arteries
- Posterior communicating arteries
-
Posterior circulation
- Vertebral arteries
- Basilar artery
- Posterior cerebral arteries
- Anterior and posterior inferior cerebellar arteries (AICA/PICA)
- Superior cerebellar arteries
-
Anterior circulation
- Veins ⇒ Deep venous system
- Cortical veins
Vascular structures can only be seen on CT if IV contrast is administered.
9
Q
Indications for CT
A
- Acute trauma
- Altered mental status
- Acute headache
- Acute neurologic deficits (stroke)
- Ventriculoperitoneal shunt malfunction
- Orbital and mastoid infection
- Chronic hearing loss
- Chronic ⇒ Abnormal head shape
10
Q
Computed Tomography (CT)
Indications for IV Contrast
A
-
Non-contrast CT Indications
- Trauma
- Stroke
- Shunt studies
- Temporal bone anatomy (hearing loss)
- Bony/skull evaluation
-
Contrast CT Indications
- Infection
- Cerebral Abscess
- Orbital cellulitis
- Mastoiditis
- Known tumor
- Metastatic disease
11
Q
Pathology on CT
A
-
Definitive evaluation:
- Intracranial hemorrhage
- Skull/facial bone fracture
- Craniosynostosis (early closure of suture)
- Soft tissue infection (orbital cellulitis, mastoiditis)
- Ventriculoperitoneal shunt malfunction
-
Screening evaluation:
- Cerebrovascular Accident (CVA)
- Masses
- Intracranial infection
- Acute
- Chronic (TORCH)
12
Q
Hemorrhage
A
Blood is hyperdense (bright) compared to brain
- Intraparenchymal ⇒ trauma, HTN, tumor, ruptured vascular malformation
-
Extraparenchymal
- Subdural ⇒ trauma (shear injury), post-surgery
- Epidural ⇒ trauma (direct)
- Subarachnoid ⇒ ruptured aneurysm, trauma
- Intraventricular ⇒ trauma, ruptured vascular malformation, premature newborns
13
Q
Cerebrovascular Accident
A
- Variety of etiologies: Thrombus, embolus, HTN/hemorrhage
-
Appearance on CT varies according to the timing of initial insult
- Immediate: Hyperdense thrombus in affected vessel
- Early (1-6 hours): Loss of gray-white differentiation, gyral swelling
- Subacute (1st and 2nd week): Increasing, then decreasing swelling
- Chronic: Volume loss
14
Q
Magnetic Resonance Imaging (MRI)
Advantages vs Disadvantages
A
-
MRI Advantages
- No ionizing radiation
- Contrast enhancement with Gadolinium
- Less likely to cause allergic reaction than iodinated contrast
- Superb demonstration of brain anatomy and pathology
- Can visualize vessels without contrast
- Can do fetal MRI
-
MRI Disadvantages
- High cost, limited availability
- Not portable
- Studies take up to 1-2 hours
- Sedation may be required
- Contraindicated in some patients
- Pacemakers, cochlear implants, embedded metal
- Gadolinium deposits in basal ganglia
- So far, uncertain consequences
-
IV contrast cannot be given to patients with end stage renal disease
- Gadolinium can cause nephrogenic systemic fibrosis, a potentially fatal scleroderma-like syndrome
15
Q
MRI
Planes
A
16
Q
MRI
Imaging Types
A
Variety of types of MRI (Ex. T1-weighted, T2-weighted, FLAIR) which can be performed to emphasize certain structures or abnormalities.
19
Q
Indications for MR Angiography
A
-
Concern for aneurysm or other vascular malformation
- Screening
- Family history
- Autosomal dominant polycystic kidney disease
- Intracerebral hemorrhage concerning for vascular malformation
- Screening
-
Concern for dural venous sinus thrombosis
- Headache and hypercoagulability
- Complicated infection (meningitis, mastoiditis)
22
Q
Angiography
(Arteriography)
A
-
Invasive procedure, performed under fluoroscopic guidance
- Arterial puncture (most commonly femoral, but also brachial, axillary, etc.) is performed
- Introduction of a guide wire over which a small-caliber vascular catheter is threaded
- Catheter tip is guided into the artery of interest
- Contrast medium injected through catheter tip to visualize arteries/veins in area of interest
- Conventional angiography is used for demonstration of vascular abnormalities such as aneurysms and arteriovenous malformations (AVM)
- “Gold standard” for demonstrating anatomy of small arteries and veins
- For diagnosis, largely replaced by CT angiography (CTA) and MR angiography (MRA)
- Widely used for intravascular therapy ⇒ lysis of thrombus, occlusion of aneurysms and AVMs
23
Q
Nuclear Medicine
Overview
A
- Utilizes radioactive substance (radionuclides) in the dx and tx of disease
- Radionuclides + other elements or pharmaceuticals → radiopharmaceuticals
- Localize to specific organs or tissue receptors after IV admin
-
One use in neuro imaging is in brain death
- Brain death ⇒ no uptake of tracer within brain parenchyma
- Surrounding soft tissues remain perfused
