Imaging Procedures Flashcards
Brain Thin sections (2-5 mm) are acquired from \_\_\_\_\_\_\_
Then 5 -10 mm slices _______
Skull base through the posterior fossa
Through the vertex
Thin sections through the pf _______
Reduce beam-hardening artifact caused by the petrous pyramids
Windows to see gray/white matter of the brain
WL 35
WW 100
Window to see bone on brain
WL 400
WW 3000
Window to see hemorrhage/hematoma on brain
WL 75
WW 150
Window to see acute ischemia on brain
WL 35
WW 25
Variable, high contrast windowing improves the CT visualization of acute stroke
The pixel value, given in Hounsfield units (HU), at the center of the window width. Controls the brightness (density) of the CT image
Window level (WL)
The range of pixel values assigned a shade of gray in the displayed CT image. Controls the contrast of the CT image
Window width (WW)
When IV contrast should be used for the brain
- arteriovenous malformation
- suspected neoplasm
- attention to the pituitary gland
High spatial frequency is what algorithm
Bone
Soft tissue window for orbits
WL 40
WW 400
Bone window for orbits
WL 400
WW 3000
Protocol for imaging the orbits
Axial
Thin slices (1-3 mm)
Parallel to the IOML
Protocol for imagining the sinuses/facial bones
Axial
Parallel to the hard palate
Soft tissue window for sinuses/facial bones
WL 40
WW 400
Bone window for sinuses/facial bones
WL 400
WW 3000
Vascular components of the circle of Willis
- right and left anterior cerebral arteries
- anterior communicating artery
- right and left internal carotid arteries
- right and left posterior cerebral arteries
- right and left posterior communicating arteries
CTA brain protocol
Thin slices (.5-1.5 mm)
Helical
Caudocranial direction
From C2 to at least 1 cm above the dorsum sella.
(If 16 slice or greater machine-may extend through the vertex)
Dorsum sellae
Forms posterior wall of sella turcica, which houses the pituitary gland
Level of blood flow throughout brain tissue
Cerebral perfusion
Amount of blood (mL) contained within a 100-g volume of brain tissue.
Normal range is 4 to 5 mL/100g
Cerebral blood volume (CBV)
Amount of blood (mL) that moves through 100 g of brain tissue each minute.
Normal range in gray matter is 50 to 60 mL/100g/min
Cerebral blood flow (CBF)
CBF = CBV/
MTT
Average transit time (sec) for blood to pass through a given region of brain tissue
Mean transit time (MTT)