Computed Tomography Exam Questions And Correct Detailed
Answers New Updated Version
26
CT basics - CORRECT ANSWER=·Essentially an x-ray tube that rotates round the pt
20
·Table moves, feeding pt into the gantry
·Each large is data collected as a series of slices
am
o Each slice is divided into voxels (volume elements)
Each sweep of the source-detector around the body during CT is called a
. - CORRECT ANSWER=translation
Ex
Each CT projection records variations in
.- CORRECT ANSWER=mass density and effective atomic number
s
rt
Each CT projection is .
pe
1. printed on film
2. stored on the computer
Ex
3. displayed on the monitor - CORRECT ANSWER=stored on the computer
The cross-sectional anatomy is translated into
during CT reconstruction. - CORRECT ANSWER=amatrix of values
,The first generation of computed tomography used detector (s). - CORRECT
ANSWER=one
The principal drawback of the first-generation CT scanner was the .- CORRECT
ANSWER=long scanning time
6
What is windowing? - CORRECT ANSWER=Amethod in which the CT image gray scale can be
2
manipulated in order to enhance different structures of varying tissues
20
What are the 2 windowing mechanisms? - CORRECT ANSWER=- Window width
- Window level
am
What is Window Width (WW)? - CORRECT ANSWER=- The range of the CT numbers in the image
Ex
- Determines the maximum number of shades of gray that can be displayed on the CT monitor
- Effects contrast
ts
What is Window Level (WL)? - CORRECT ANSWER=- The center or midpoint of the range of CT
r
numbers
pe
- Effects brightness
Ex
Wide window widths (400 to 2000 HU) are necessary for ?- CORRECT
ANSWER=Varying body tissues
Narrow window widths (50 to 350 HU) are necessary for ? - CORRECT
ANSWER=Different tissues of similar densities
,What are the effects of WW on image contrast? - CORRECT ANSWER=- As the WW
increases, the contrast decreases
- As the WW decreases, the contrast increases
26
What are the effects of WL on image brightness? - CORRECT ANSWER=- Moving the WL
toward the higher CT numbers results in a darker image
20
- Moving the WL toward the lower CT numbers results in a brighter image
am
What is a multi-slice scanner (MSCT)? - CORRECT ANSWER=- CTsystem equipped with a
multiple-row detector array to simultaneously collect data at different slice locations
- Can scan up to 64 slices
Ex
In CT, the attenuated image-forming radiation is detected by what? - CORRECT
ANSWER=A solid state image receptor
s
rt
What is Helical CT? - CORRECT ANSWER=- Continuous gantry rotation + continuous table
pe
feed
- Scan data traces a helical path or spiral around patient
Ex
What is Isotropic Imaging? -CORRECTANSWER=2Dpixel in a CT image represents a 3D voxel
Name the 3 types of Data acquisition systems? - CORRECT ANSWER=- Conventional
, - Helical single slice (spiral)
- Multi-slice
What is a Linear Attenuation coefficient? - CORRECT ANSWER=Characterizes how easily a volume of
material can be penetrated by the x-rays
2 6
20
What is a bowtie filter? - CORRECT ANSWER=Used to allow a uniform beam to reach detectors
What occurs with CT filtration? - CORRECT ANSWER=- Removes long wavelength x-rays which
contributes to patient dose am
- 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
Ex
What is pitch? What is the formula? - CORRECT ANSWER=Relationship between the patient couch
ts
movement and the x-ray beam collimation and is expressed as a ratio
r
pe
Pitch = Couch movement each 360 degrees / Slice Thickness
How do different structures appear on CT? - CORRECT ANSWER=- Bone and high density structures,
Ex
such as radiopaque contrast media, appear white
- Air and other low density structures appear black
- Fat and organs appear in varying shades of gray
Answers New Updated Version
26
CT basics - CORRECT ANSWER=·Essentially an x-ray tube that rotates round the pt
20
·Table moves, feeding pt into the gantry
·Each large is data collected as a series of slices
am
o Each slice is divided into voxels (volume elements)
Each sweep of the source-detector around the body during CT is called a
. - CORRECT ANSWER=translation
Ex
Each CT projection records variations in
.- CORRECT ANSWER=mass density and effective atomic number
s
rt
Each CT projection is .
pe
1. printed on film
2. stored on the computer
Ex
3. displayed on the monitor - CORRECT ANSWER=stored on the computer
The cross-sectional anatomy is translated into
during CT reconstruction. - CORRECT ANSWER=amatrix of values
,The first generation of computed tomography used detector (s). - CORRECT
ANSWER=one
The principal drawback of the first-generation CT scanner was the .- CORRECT
ANSWER=long scanning time
6
What is windowing? - CORRECT ANSWER=Amethod in which the CT image gray scale can be
2
manipulated in order to enhance different structures of varying tissues
20
What are the 2 windowing mechanisms? - CORRECT ANSWER=- Window width
- Window level
am
What is Window Width (WW)? - CORRECT ANSWER=- The range of the CT numbers in the image
Ex
- Determines the maximum number of shades of gray that can be displayed on the CT monitor
- Effects contrast
ts
What is Window Level (WL)? - CORRECT ANSWER=- The center or midpoint of the range of CT
r
numbers
pe
- Effects brightness
Ex
Wide window widths (400 to 2000 HU) are necessary for ?- CORRECT
ANSWER=Varying body tissues
Narrow window widths (50 to 350 HU) are necessary for ? - CORRECT
ANSWER=Different tissues of similar densities
,What are the effects of WW on image contrast? - CORRECT ANSWER=- As the WW
increases, the contrast decreases
- As the WW decreases, the contrast increases
26
What are the effects of WL on image brightness? - CORRECT ANSWER=- Moving the WL
toward the higher CT numbers results in a darker image
20
- Moving the WL toward the lower CT numbers results in a brighter image
am
What is a multi-slice scanner (MSCT)? - CORRECT ANSWER=- CTsystem equipped with a
multiple-row detector array to simultaneously collect data at different slice locations
- Can scan up to 64 slices
Ex
In CT, the attenuated image-forming radiation is detected by what? - CORRECT
ANSWER=A solid state image receptor
s
rt
What is Helical CT? - CORRECT ANSWER=- Continuous gantry rotation + continuous table
pe
feed
- Scan data traces a helical path or spiral around patient
Ex
What is Isotropic Imaging? -CORRECTANSWER=2Dpixel in a CT image represents a 3D voxel
Name the 3 types of Data acquisition systems? - CORRECT ANSWER=- Conventional
, - Helical single slice (spiral)
- Multi-slice
What is a Linear Attenuation coefficient? - CORRECT ANSWER=Characterizes how easily a volume of
material can be penetrated by the x-rays
2 6
20
What is a bowtie filter? - CORRECT ANSWER=Used to allow a uniform beam to reach detectors
What occurs with CT filtration? - CORRECT ANSWER=- Removes long wavelength x-rays which
contributes to patient dose am
- 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
Ex
What is pitch? What is the formula? - CORRECT ANSWER=Relationship between the patient couch
ts
movement and the x-ray beam collimation and is expressed as a ratio
r
pe
Pitch = Couch movement each 360 degrees / Slice Thickness
How do different structures appear on CT? - CORRECT ANSWER=- Bone and high density structures,
Ex
such as radiopaque contrast media, appear white
- Air and other low density structures appear black
- Fat and organs appear in varying shades of gray
