CT REGISTRY Exam Questions and
Answers Graded A+
how do you reduce beam hardening - Correct answer-1. Increase dose
2. Reduce collimation--Reduce slice thickness
3. Increase window width
At what level does the abdominal aortal bifurcate? - Correct answer-L4
What is the typical scan delay after injection of contrast media for studies of the
liver? - Correct answer-30-45 seconds
What window settings provide the best tissue differentiation within the liver? -
Correct answer-window width= 140, level= 60
What is the window settings that provide the best bone window for the pelvis? -
Correct answer-window width=2000, window level=350
What mAs is typically used in routine CT exams of the abdomen? - Correct
answer-200-300 mAs
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,What is the result of the bifurcation of the abdominal aorta? - Correct answer-The
right and left common iliac arteries
What is the anode target angle? - Correct answer-12 degrees
At what level do the common carotids bifurcate into the internal and external
carotid arteries? - Correct answer-C3-C4
The floor of the orbit is formed by the __________ bones. - Correct answer-
maxillary and zygomatic
The lateral wall of the orbit is formed by the ___________ bones. - Correct
answer-zygomatic and sphenoid
The medial wall of the orbit is formed by the _________ bones. - Correct answer-
ethmoid and lacrimal bones
how do you calculate effective mAs? - Correct answer-mAs/pitch
define window level and window width - Correct 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.
©COPYRIGHT 2025, ALL RIGHTS RESERVED 2
,- 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
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
, Black = <25
factors that affect spatial and contrast resolution - Correct 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
©COPYRIGHT 2025, ALL RIGHTS RESERVED 4
Answers Graded A+
how do you reduce beam hardening - Correct answer-1. Increase dose
2. Reduce collimation--Reduce slice thickness
3. Increase window width
At what level does the abdominal aortal bifurcate? - Correct answer-L4
What is the typical scan delay after injection of contrast media for studies of the
liver? - Correct answer-30-45 seconds
What window settings provide the best tissue differentiation within the liver? -
Correct answer-window width= 140, level= 60
What is the window settings that provide the best bone window for the pelvis? -
Correct answer-window width=2000, window level=350
What mAs is typically used in routine CT exams of the abdomen? - Correct
answer-200-300 mAs
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,What is the result of the bifurcation of the abdominal aorta? - Correct answer-The
right and left common iliac arteries
What is the anode target angle? - Correct answer-12 degrees
At what level do the common carotids bifurcate into the internal and external
carotid arteries? - Correct answer-C3-C4
The floor of the orbit is formed by the __________ bones. - Correct answer-
maxillary and zygomatic
The lateral wall of the orbit is formed by the ___________ bones. - Correct
answer-zygomatic and sphenoid
The medial wall of the orbit is formed by the _________ bones. - Correct answer-
ethmoid and lacrimal bones
how do you calculate effective mAs? - Correct answer-mAs/pitch
define window level and window width - Correct 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.
©COPYRIGHT 2025, ALL RIGHTS RESERVED 2
,- 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
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
, Black = <25
factors that affect spatial and contrast resolution - Correct 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
©COPYRIGHT 2025, ALL RIGHTS RESERVED 4
