CSI CDT COMPREHENSIVE CONSTRUCTION
SPECIFICATIONS REVIEW SHEET FULL
SOLUTIONS
●● At what level does the abdominal aortal bifurcate?
Answer: L4
●● What is the typical scan delay after injection of contrast media for
studies of the liver?
Answer: 30-45 seconds
●● What window settings provide the best tissue differentiation within
the liver?
Answer: window width= 140, level= 60
●● What is the window settings that provide the best bone window for
the pelvis?
Answer: window width=2000, window level=350
●● What mAs is typically used in routine CT exams of the abdomen?
Answer: 200-300 mAs
,●● What is the result of the bifurcation of the abdominal aorta?
Answer: The right and left common iliac arteries
●● What is the anode target angle?
Answer: 12 degrees
●● At what level do the common carotids bifurcate into the internal and
external carotid arteries?
Answer: C3-C4
●● The floor of the orbit is formed by the __________ bones.
Answer: maxillary and zygomatic
●● The lateral wall of the orbit is formed by the ___________ bones.
Answer: zygomatic and sphenoid
●● The medial wall of the orbit is formed by the _________ bones.
Answer: ethmoid and lacrimal bones
●● how do you calculate effective mAs?
Answer: mAs/pitch
,●● define window level and window width
Answer: LEVEL: a chosen midpoint in the grayscale
WIDTH: number of grayscale values above and below the level.
- The width is DIVIDED in HALF and distributed above and below the
level.
- Anything above the window is white
- Anything below the window is black
The wider the window the more grayscale values, the lower the contrast!
example:
Level 100, Width 300
White = >+250
Black = <-50
Level 100, Width 200
White = >+200
Black = <0
Level 100, Width 150
White = >+175
, Black = <25
●● factors that affect spatial and contrast resolution
Answer: Spatial resolution:
1) focal spot
2) detector width (aperture)
3) reconstruction algorithm - bone>soft tissue
4) slice thickness - thinner is better
5) pixel/FOV/matrix
6) pitch - decreased pitch means no gaps
7) nyquist limitations
Contrast resolution: CNR
1) energy of X-rays - kVp - ↑ kVp ↓ contrast
2) number of X-rays - mA - ↑ mA ↓ mottle
3) slice thickness - thicker is better
4) reconstruction method - iterative > filtered
5) reconstruction algorthith - soft tissue>bone
●● Give window levels for brain, lung, abdomen, bone
Answer: Brain: W80,L+40
Lung: W1500, L-400
SPECIFICATIONS REVIEW SHEET FULL
SOLUTIONS
●● At what level does the abdominal aortal bifurcate?
Answer: L4
●● What is the typical scan delay after injection of contrast media for
studies of the liver?
Answer: 30-45 seconds
●● What window settings provide the best tissue differentiation within
the liver?
Answer: window width= 140, level= 60
●● What is the window settings that provide the best bone window for
the pelvis?
Answer: window width=2000, window level=350
●● What mAs is typically used in routine CT exams of the abdomen?
Answer: 200-300 mAs
,●● What is the result of the bifurcation of the abdominal aorta?
Answer: The right and left common iliac arteries
●● What is the anode target angle?
Answer: 12 degrees
●● At what level do the common carotids bifurcate into the internal and
external carotid arteries?
Answer: C3-C4
●● The floor of the orbit is formed by the __________ bones.
Answer: maxillary and zygomatic
●● The lateral wall of the orbit is formed by the ___________ bones.
Answer: zygomatic and sphenoid
●● The medial wall of the orbit is formed by the _________ bones.
Answer: ethmoid and lacrimal bones
●● how do you calculate effective mAs?
Answer: mAs/pitch
,●● define window level and window width
Answer: LEVEL: a chosen midpoint in the grayscale
WIDTH: number of grayscale values above and below the level.
- The width is DIVIDED in HALF and distributed above and below the
level.
- Anything above the window is white
- Anything below the window is black
The wider the window the more grayscale values, the lower the contrast!
example:
Level 100, Width 300
White = >+250
Black = <-50
Level 100, Width 200
White = >+200
Black = <0
Level 100, Width 150
White = >+175
, Black = <25
●● factors that affect spatial and contrast resolution
Answer: Spatial resolution:
1) focal spot
2) detector width (aperture)
3) reconstruction algorithm - bone>soft tissue
4) slice thickness - thinner is better
5) pixel/FOV/matrix
6) pitch - decreased pitch means no gaps
7) nyquist limitations
Contrast resolution: CNR
1) energy of X-rays - kVp - ↑ kVp ↓ contrast
2) number of X-rays - mA - ↑ mA ↓ mottle
3) slice thickness - thicker is better
4) reconstruction method - iterative > filtered
5) reconstruction algorthith - soft tissue>bone
●● Give window levels for brain, lung, abdomen, bone
Answer: Brain: W80,L+40
Lung: W1500, L-400
