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)
Primary indication for CTP (CT perfusion)
Evaluation of acute stroke
Beyond repair by thrombolytic therapy.
CBV less than 2.5mL/100g
Brain tissue within infarct core
Ischemic yet still viable tissue immediately surrounding the infarct core.
CBV is still greater than 2.5mL/100g
Penumbra
Mathematical technique utilized for generation of perfusion maps
Deconvolution
Soft tissue neck protocol
Helical axial plane
From superior orbital rim inferiorly through the king apex
Soft tissue settings for soft tissue neck
WL 50
WW 400
Bone setting for soft tissue neck
WL 300
WW 2000
Lung parenchyma settings for a chest
WL -450
WW 1400
Mediastinum settings for a chest
WL 40
WW 350
Bone setting for a chest
WL 300
WW 2000
Data acquired only when heart is at rest (diastole)
Prospective gating or triggering
Only data acquired during diastole is used for reconstruction
Retrospective gating
Ability of a CT system to freeze motion and provide an image free of blurring
Temporal resolution
Portion of the cardiac cycle in which coronary artery motion velocity is slowest and cardiac motion is at its lowest
Ventricular diastole
Soft tissue setting for abdomen
WL 40
WW 350
Lung bases setting for abdomen
WL -450
WW 1400
Bone setting for abdomen
WL 300
WW 2000
Liver receives 75% of its supply from the ______ vein and the remaining 25% from the _______ artery
Portal vein
Hepatic artery
Perks arterial enhancement.
25-35 sec after contrast administration
Arterial phase
Peak hepatic parenchymal enhancement.
60-70 sec after contrast administration
Portal (or hepatic) venous phase
Hepatic parenchymal enhancement dissipates and minimal difference in contrast enhancement between intravascular and extravascular spaces.
2-3 min after contrast administration
Equilibrium phase
Optimal phase for angiographic applications of liver
Early arterial (15-20 sec)
HU of unenhanced spleen
+40 to +60 HU
Approximately 10 HU less than unenhanced liver
Imaging phase of spleen
Portal venous phase (60-70 sec)
Phase of optimal pancreatic parenchymal enhancement
Delayed arterial phase (35-45 sec)
Resection of the pancreas and duodenum
Whipple procedure
Adrenal glad density (HU)
Similar to muscle (25-40 HU)
Adrenal gland acquisition
Portal venous phase (69-70 sec)
Delayed (10-15 min) for tumor characterization
Pre-contrast ROI measurement of less than 10 HU indicates
Benign
Delayed post-contrast imaging, metastatic lesions of adrenal glands remain enhanced _______ than adrenal adenonas
Longer
GI tract acquisition phase
Portal venous for optimal gastric and intestinal wall enhancement
Soft tissue settings for spine
WL 50
WW 400
Bone settings for spine
WL 300
WW 2000
Soft tissue settings for extremities
WL 50
WW 400
Bone settings for extremities
WL 300
WW 2000
PET uses which pharmaceutical
Fludeoxyglucose F 18 (FDG)
