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What is windowing? correct answers A method in which the CT image gray scale can be
manipulated in order to enhance different structures of varying tissues
What are the 2 windowing mechanisms? correct answers - Window width
- Window level
What is Window Width (WW)? correct answers - The range of the CT numbers in the image
- Determines the maximum number of shades of gray that can be displayed on the CT monitor
- Effects contrast
What is Window Level (WL)? correct answers - The center or midpoint of the range of CT
numbers
- Effects brightness
Wide window widths (400 to 2000 HU) are necessary for ____? correct answers Varying body
tissues
Narrow window widths (50 to 350 HU) are necessary for ____? correct answers Different tissues
of similar densities
What are the effects of WW on image contrast? correct answers - As the WW increases, the
contrast decreases
- As the WW decreases, the contrast increases
What are the effects of WL on image brightness? correct answers - Moving the WL toward the
higher CT numbers results in a darker image
- Moving the WL toward the lower CT numbers results in a brighter image
What is a multi-slice scanner (MSCT)? correct answers - CT system equipped with a multiple-
row detector array to simultaneously collect data at different slice locations
- Can scan up to 64 slices
In CT, the attenuated image-forming radiation is detected by what? correct answers A solid state
image receptor
What is Helical CT? correct answers - Continuous gantry rotation + continuous table feed
- Scan data traces a helical path or spiral around patient
What is Isotropic Imaging? correct answers 2D pixel in a CT image represents a 3D voxel
Name the 3 types of Data acquisition systems? correct answers - Conventional
- Helical single slice (spiral)
- Multi-slice
,What is a Linear Attenuation coefficient? correct answers Characterizes how easily a volume of
material can be penetrated by the x-rays
What is a bowtie filter? correct answers Used to allow a uniform beam to reach detectors
What occurs with CT filtration? correct answers - Removes long wavelength x-rays which
contributes to patient dose
- Shapes the energy distribution across the radiation beam to produce uniform beam hardening
when x-rays pass through the filter and the object causing beam hardening artifacts
What is pitch? What is the formula? correct answers Relationship between the patient couch
movement and the x-ray beam collimation and is expressed as a ratio
Pitch = Couch movement each 360 degrees / Slice Thickness
How do different structures appear on CT? correct answers - Bone and high density structures,
such as radiopaque contrast media, appear white
- Air and other low density structures appear black
- Fat and organs appear in varying shades of gray
What are two types of brain tumours? correct answers - Primary brain tumour: grows originally
in the brain
- Secondary brain tumour: A tumour that has spread to the brain from a different site in the body
such as lungs, bowel
What is hydrocephalus? How does it appear on a CT scan? correct answers - Congenital disease
where a child is unable to drain excess CSF
- Can also be acquired as an adult
- Ventricles appear enlarged and very black
Multi-phasic imaging is frequently used for what studies? correct answers Specialized studies of
the pancreas, liver, and kidney as well as in many abdominal CTA protocols
For most protocols of the abdomen or pelvis, patients are scanned in what position? correct
answers The supine position with the arms elevated
Patients are asked to suspend respiration during image acquisition to reduce ____ and decrease
artifact? correct answers Movement
What are 2 common pathologies seen in the liver with CT? correct answers - Fatty infiltrates
- Cavernous hemangioma
The liver is most often scanned during what contrast phase? correct answers The portal venous
phase
, Measurements from a CT image of the abdomen show the liver density is 35 HU whereas the
density of the spleen is 65 HU. Which is a likely diagnosis?
a. Metastatic disease of the liver
b. Cavernous hemangioma
c. Fatty infiltrate
d. Ruptured spleen correct answers When the liver measurement is at least 10 HU lower than that
of the spleen, fatty infiltrate of the liver is indicated
When initial scans fail to differentiate the margins of the pancreas from the duodenum, the
patient is often given additional oral CM and slices are obtained in what position? correct
answers With the patient in the right decubitus position
Enhancement phases of the urinary tract include? correct answers - Corticomedullary phase, 30
to 70 s after CM bolus
- Nephrogram phase, 100 to 120 s after CM bolus
- Excretory phase, 3 minutes after CM bolus
What are the two unique features of adenomas on CT used to differentiate benign from
malignant lesions? correct answers - Intracellular lipid (fat) content
- CM washout (can only be evaluated if delayed images are acquired)
Kidney stones can be viewed best on? correct answers Non-contrast helical CT
What is the protocol for scanning the kidneys? correct answers Use a helical scan mode from the
top of the kidneys to the base of the bladder and a slice thickness of 3 mm or less
A ____ scan time helps to reduce artifacts created by respiratory motion? correct answers Short
Scans of the chest should be acquired with what breathing technique? correct answers A single
breath-hold (Full inspiration)
What occurs when an operator reduces the scan of field of view? correct answers A lower
number of detectors is activated
What does predetector collimation do? correct answers Removes scatter radiation from reaching
the detectors
What methods can be used to reduce radiation to pediatric patients? correct answers - Reduce
mA
- Limit phases of acquisition
- Increase pitch
During a CT arthrography, contrast media is injected directly into what? correct answers Joint
space
What is windowing? correct answers A method in which the CT image gray scale can be
manipulated in order to enhance different structures of varying tissues
What are the 2 windowing mechanisms? correct answers - Window width
- Window level
What is Window Width (WW)? correct answers - The range of the CT numbers in the image
- Determines the maximum number of shades of gray that can be displayed on the CT monitor
- Effects contrast
What is Window Level (WL)? correct answers - The center or midpoint of the range of CT
numbers
- Effects brightness
Wide window widths (400 to 2000 HU) are necessary for ____? correct answers Varying body
tissues
Narrow window widths (50 to 350 HU) are necessary for ____? correct answers Different tissues
of similar densities
What are the effects of WW on image contrast? correct answers - As the WW increases, the
contrast decreases
- As the WW decreases, the contrast increases
What are the effects of WL on image brightness? correct answers - Moving the WL toward the
higher CT numbers results in a darker image
- Moving the WL toward the lower CT numbers results in a brighter image
What is a multi-slice scanner (MSCT)? correct answers - CT system equipped with a multiple-
row detector array to simultaneously collect data at different slice locations
- Can scan up to 64 slices
In CT, the attenuated image-forming radiation is detected by what? correct answers A solid state
image receptor
What is Helical CT? correct answers - Continuous gantry rotation + continuous table feed
- Scan data traces a helical path or spiral around patient
What is Isotropic Imaging? correct answers 2D pixel in a CT image represents a 3D voxel
Name the 3 types of Data acquisition systems? correct answers - Conventional
- Helical single slice (spiral)
- Multi-slice
,What is a Linear Attenuation coefficient? correct answers Characterizes how easily a volume of
material can be penetrated by the x-rays
What is a bowtie filter? correct answers Used to allow a uniform beam to reach detectors
What occurs with CT filtration? correct answers - Removes long wavelength x-rays which
contributes to patient dose
- Shapes the energy distribution across the radiation beam to produce uniform beam hardening
when x-rays pass through the filter and the object causing beam hardening artifacts
What is pitch? What is the formula? correct answers Relationship between the patient couch
movement and the x-ray beam collimation and is expressed as a ratio
Pitch = Couch movement each 360 degrees / Slice Thickness
How do different structures appear on CT? correct answers - Bone and high density structures,
such as radiopaque contrast media, appear white
- Air and other low density structures appear black
- Fat and organs appear in varying shades of gray
What are two types of brain tumours? correct answers - Primary brain tumour: grows originally
in the brain
- Secondary brain tumour: A tumour that has spread to the brain from a different site in the body
such as lungs, bowel
What is hydrocephalus? How does it appear on a CT scan? correct answers - Congenital disease
where a child is unable to drain excess CSF
- Can also be acquired as an adult
- Ventricles appear enlarged and very black
Multi-phasic imaging is frequently used for what studies? correct answers Specialized studies of
the pancreas, liver, and kidney as well as in many abdominal CTA protocols
For most protocols of the abdomen or pelvis, patients are scanned in what position? correct
answers The supine position with the arms elevated
Patients are asked to suspend respiration during image acquisition to reduce ____ and decrease
artifact? correct answers Movement
What are 2 common pathologies seen in the liver with CT? correct answers - Fatty infiltrates
- Cavernous hemangioma
The liver is most often scanned during what contrast phase? correct answers The portal venous
phase
, Measurements from a CT image of the abdomen show the liver density is 35 HU whereas the
density of the spleen is 65 HU. Which is a likely diagnosis?
a. Metastatic disease of the liver
b. Cavernous hemangioma
c. Fatty infiltrate
d. Ruptured spleen correct answers When the liver measurement is at least 10 HU lower than that
of the spleen, fatty infiltrate of the liver is indicated
When initial scans fail to differentiate the margins of the pancreas from the duodenum, the
patient is often given additional oral CM and slices are obtained in what position? correct
answers With the patient in the right decubitus position
Enhancement phases of the urinary tract include? correct answers - Corticomedullary phase, 30
to 70 s after CM bolus
- Nephrogram phase, 100 to 120 s after CM bolus
- Excretory phase, 3 minutes after CM bolus
What are the two unique features of adenomas on CT used to differentiate benign from
malignant lesions? correct answers - Intracellular lipid (fat) content
- CM washout (can only be evaluated if delayed images are acquired)
Kidney stones can be viewed best on? correct answers Non-contrast helical CT
What is the protocol for scanning the kidneys? correct answers Use a helical scan mode from the
top of the kidneys to the base of the bladder and a slice thickness of 3 mm or less
A ____ scan time helps to reduce artifacts created by respiratory motion? correct answers Short
Scans of the chest should be acquired with what breathing technique? correct answers A single
breath-hold (Full inspiration)
What occurs when an operator reduces the scan of field of view? correct answers A lower
number of detectors is activated
What does predetector collimation do? correct answers Removes scatter radiation from reaching
the detectors
What methods can be used to reduce radiation to pediatric patients? correct answers - Reduce
mA
- Limit phases of acquisition
- Increase pitch
During a CT arthrography, contrast media is injected directly into what? correct answers Joint
space
