CT REGISTRY- STUDY THIS AND YOU'LL
PASS!! EXAM QUESTIONS WITH 100%
VERIFIED COMPLETE SOLUTIONS
how do you reduce beam hardening - VERIFIED ANSWER✔✔-1. Increase dose
2. Reduce collimation--Reduce slice thickness
3. Increase window width
At what level does the abdominal aortal bifurcate? - VERIFIED ANSWER✔✔-L4
What is the typical scan delay after injection of contrast media for studies of the liver? - VERIFIED
ANSWER✔✔-30-45 seconds
What window settings provide the best tissue differentiation within the liver? - VERIFIED ANSWER✔✔-
window width= 140, level= 60
What is the window settings that provide the best bone window for the pelvis? - VERIFIED ANSWER✔✔-
window width=2000, window level=350
What mAs is typically used in routine CT exams of the abdomen? - VERIFIED ANSWER✔✔-200-300 mAs
What is the result of the bifurcation of the abdominal aorta? - VERIFIED ANSWER✔✔-The right and left
common iliac arteries
What is the anode target angle? - VERIFIED ANSWER✔✔-12 degrees
At what level do the common carotids bifurcate into the internal and external carotid arteries? - VERIFIED
ANSWER✔✔-C3-C4
The floor of the orbit is formed by the __________ bones. - VERIFIED ANSWER✔✔-maxillary and zygomatic
The lateral wall of the orbit is formed by the ___________ bones. - VERIFIED ANSWER✔✔-zygomatic and
sphenoid
The medial wall of the orbit is formed by the _________ bones. - VERIFIED ANSWER✔✔-ethmoid and
lacrimal bones
how do you calculate effective mAs? - VERIFIED ANSWER✔✔-mAs/pitch
define window level and window width - VERIFIED 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 - VERIFIED 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 - VERIFIED ANSWER✔✔-Brain: W80,L+40
Lung: W1500, L-400
Abdomen: W400, L+50
Bone: W1600, L+500
What is beam hardening?
what are the two types of beam hardening artifact?
how do you compensate for it? - VERIFIED ANSWER✔✔-1) as the X-ray beam passes through an object, lower
energy photons are removed (like filtration!) leaving a "harder beam" of high energy photons. This causes two
artifacts:
2) Cupping: the center of a round object is darker than the periphery due to hardening of the beam 360 degrees
around the object. happens in the head
3) Streak: these are dark bands that occur in between two dense objects - nearly all the photons are removed in a
line between the two objects
4) fixes:
A) Filtration: pre-hardening the beam to remove low energy photons
B) Calibration: using a phantom to set a compensated mA/kVp
C) Correct software: iterative reconstruction may help
D) Avoidance: tilting the gantry of positioning the patient to avoid areas that may cause hardening.
ring artifact - VERIFIED ANSWER✔✔-Calibration error or defective detector cause consistently erroneous
reading at each angular position, resulting in a circular artifact
is the focal spot large or small? - VERIFIED ANSWER✔✔-large 0.6-1.2 - so as not to overheat the anode from
such a high mA
Which of the following will result in an increased voxel size: B increased slice thickness - VERIFIED
ANSWER✔✔-A)decreased reconstruction FOV B) increased slice thickness C) increased matrix D) none of these
,If a tissue with a CT number of +300 appears white on the image, which of the following are the window width
and window level selected: A)window level =0, window width =500 B)window level= +300, window width= 500
C)window level =+100, window width =1000 D)none of these - VERIFIED ANSWER✔✔-A) window level =0,
window width =500
What is the volume of a voxel if a slice thickness of 3 mm, a 512x512 matrix & a reconstruction field of view of
25.6cm are used A) 0.75mm³ B)1.5mm³ C) 6.0mm³ D)none of these - VERIFIED ANSWER✔✔-A. Solve this by
finding the pixel size first FOV/matrix size ... that is 0.5 ... now square that 0.25 .... multiply that by slice
thickness and you get 0.75
Which of the following parameters is responsible for partial volume averaging: A) matrix size B) kVp C)slice
thickness D) patient dose - VERIFIED ANSWER✔✔-C
Voxel equation - VERIFIED ANSWER✔✔-pixel area x section thickness
What is interpolation? - VERIFIED ANSWER✔✔-Mathematical method for taking SPIRAL data and viewing it
as AXIAL images
Bone windows - VERIFIED ANSWER✔✔-2000-4000 WW
200-400 WL
Lung windows - VERIFIED ANSWER✔✔-1400-1600 WW
(-)400-600 WL
Modular Transfer Function? - VERIFIED ANSWER✔✔-graphical representation of SPATIAL RESOLUTION
measured in lp/cm, tells how small you can scan without blurring
Decrease partial volume averaging? - VERIFIED ANSWER✔✔-Reduce slice thickness
Which portion of the pancreas is the most common site for tumors?; and where located? - VERIFIED
ANSWER✔✔-The head of the pancreas. It is located approximately at T12
LUNG WINDOW
(-) IS AIR - VERIFIED ANSWER✔✔-2000 WW and -200 WL =
The Hounsfield unit that is -1000 most likely represents which of the following? - VERIFIED ANSWER✔✔-Air
Relative to CT topography, slice thickness is best represented by which of the following axes? - VERIFIED
ANSWER✔✔-Z axis
What unit is the basis for exposure based on ionization in air? - VERIFIED ANSWER✔✔-mR or C/kg
What radiation unit considers the biological effectiveness of radiation exposure? - VERIFIED ANSWER✔✔-
mrem or mSv
"Fan" beam technology first historically came on the scene with which acquisition geometries? - VERIFIED
ANSWER✔✔-Second
"Rotate-rotate" applies to which of the following geometries? - VERIFIED ANSWER✔✔-Third
In CT what imaging plane is the pituitary best visualized? - VERIFIED ANSWER✔✔-coronal
The third ventricle of the brain communicates with the fourth ventricle through the - VERIFIED ANSWER✔✔-
Cerebral aqueduct
refers to an excessive Amount of nitrogenous materials in the blood and is a symptom of renal failure. -
VERIFIED ANSWER✔✔-Azotemia
, Which paranasal sinus is usually the last to fully develop? - VERIFIED ANSWER✔✔-Frontal
What is the average annual radiation dose? - VERIFIED ANSWER✔✔-2 rem
10 rem converted to Sieverts is what? - VERIFIED ANSWER✔✔-0.1 Sv
convert 10 mSv to Sv - VERIFIED ANSWER✔✔-0.01 sV
annual limit for adult occupational effective dose? - VERIFIED ANSWER✔✔-0.05 Sv
annual limit of occupational lens dose - VERIFIED ANSWER✔✔-0.15 Sv
annual limit of shallow dose equivalent to skin/extremities - VERIFIED ANSWER✔✔-0.5 Sv
occupational exposure to embryo/fetus during pregnancy - VERIFIED ANSWER✔✔-0.5 mSv
total effective dose equivalent to public
--also average background radiation - VERIFIED ANSWER✔✔-1 mSv
Mild reactions to iodinated intravenous contrast media include - VERIFIED ANSWER✔✔-nausea, vomiting,
mild urticaria, and a warm flushed sensation
Moderate reactions? - VERIFIED ANSWER✔✔-Dyspnea, Hives (urticarial); wheezing (mild bronchospasm);
change in pulse; facial edema; vasovagal response; hypo- or hypertension
Severe reactions? - VERIFIED ANSWER✔✔-Severe bronchospasm; anaphylaxis; Drowsiness; headache;
fever/chills, Shock, pulmonary edema
Osmolality - VERIFIED ANSWER✔✔-Concentration of a solution in terms of number of dissolved particles per
unit of water
Non-ionic intravenous contrast media such as Omnipaque should have an average osmolality of - VERIFIED
ANSWER✔✔-750 mOsm/kg water
What drugs are administered for moderate reaction to injection of iodinated contrast medium - VERIFIED
ANSWER✔✔-Antihistamines
Epinephrine
Prothrombin measures the amount of time necessary for a person's blood to coagulate - VERIFIED
ANSWER✔✔-normal limits: between 10 and 14 seconds
why use an autoclave? - VERIFIED ANSWER✔✔-The use of an autoclave for sterilization involves heat and
steam under pressure to eliminate microbes.
1 rem= 1 rad - VERIFIED ANSWER✔✔-When measuring the radiation dose from x-rays, rads and rems are
equivalent. The units of Sv and rem are used to measure any kind of ionizing radiation where 1 Sv =100rem. The
units of rad and Gy are used to measure specifically x-ray radiation where 1 Gy = 100 rads.
When performing a multi-slice CT study, the slice thickness may be ___________ to cover the region of interest,
in order to minimize the dose to the patient. - VERIFIED ANSWER✔✔-Due to radiation penumbra, a multiple
slice study results in a greater patient dose than the same number of individual slices. By covering a specific
region of interest with fewer slices (increase in slice thickness) the resulting radiation overlap from adjacent slices
is reduced, reducing the dose to the patient.
A given CT exam yields a CTDI of 4.5 rads, with a slice thickness of 10mm, and a 2mm gap between slices, the
MSAD for this exam is ________ rads. - VERIFIED ANSWER✔✔-The MSAD is equal to the CTDI X the ratio
of the slice thickness to the table increment. With a 2mm gap and a 10mm slice the table increment will be 12mm.
The MSAD = (4.5 rads) X (10mm/12mm)
PASS!! EXAM QUESTIONS WITH 100%
VERIFIED COMPLETE SOLUTIONS
how do you reduce beam hardening - VERIFIED ANSWER✔✔-1. Increase dose
2. Reduce collimation--Reduce slice thickness
3. Increase window width
At what level does the abdominal aortal bifurcate? - VERIFIED ANSWER✔✔-L4
What is the typical scan delay after injection of contrast media for studies of the liver? - VERIFIED
ANSWER✔✔-30-45 seconds
What window settings provide the best tissue differentiation within the liver? - VERIFIED ANSWER✔✔-
window width= 140, level= 60
What is the window settings that provide the best bone window for the pelvis? - VERIFIED ANSWER✔✔-
window width=2000, window level=350
What mAs is typically used in routine CT exams of the abdomen? - VERIFIED ANSWER✔✔-200-300 mAs
What is the result of the bifurcation of the abdominal aorta? - VERIFIED ANSWER✔✔-The right and left
common iliac arteries
What is the anode target angle? - VERIFIED ANSWER✔✔-12 degrees
At what level do the common carotids bifurcate into the internal and external carotid arteries? - VERIFIED
ANSWER✔✔-C3-C4
The floor of the orbit is formed by the __________ bones. - VERIFIED ANSWER✔✔-maxillary and zygomatic
The lateral wall of the orbit is formed by the ___________ bones. - VERIFIED ANSWER✔✔-zygomatic and
sphenoid
The medial wall of the orbit is formed by the _________ bones. - VERIFIED ANSWER✔✔-ethmoid and
lacrimal bones
how do you calculate effective mAs? - VERIFIED ANSWER✔✔-mAs/pitch
define window level and window width - VERIFIED 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 - VERIFIED 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 - VERIFIED ANSWER✔✔-Brain: W80,L+40
Lung: W1500, L-400
Abdomen: W400, L+50
Bone: W1600, L+500
What is beam hardening?
what are the two types of beam hardening artifact?
how do you compensate for it? - VERIFIED ANSWER✔✔-1) as the X-ray beam passes through an object, lower
energy photons are removed (like filtration!) leaving a "harder beam" of high energy photons. This causes two
artifacts:
2) Cupping: the center of a round object is darker than the periphery due to hardening of the beam 360 degrees
around the object. happens in the head
3) Streak: these are dark bands that occur in between two dense objects - nearly all the photons are removed in a
line between the two objects
4) fixes:
A) Filtration: pre-hardening the beam to remove low energy photons
B) Calibration: using a phantom to set a compensated mA/kVp
C) Correct software: iterative reconstruction may help
D) Avoidance: tilting the gantry of positioning the patient to avoid areas that may cause hardening.
ring artifact - VERIFIED ANSWER✔✔-Calibration error or defective detector cause consistently erroneous
reading at each angular position, resulting in a circular artifact
is the focal spot large or small? - VERIFIED ANSWER✔✔-large 0.6-1.2 - so as not to overheat the anode from
such a high mA
Which of the following will result in an increased voxel size: B increased slice thickness - VERIFIED
ANSWER✔✔-A)decreased reconstruction FOV B) increased slice thickness C) increased matrix D) none of these
,If a tissue with a CT number of +300 appears white on the image, which of the following are the window width
and window level selected: A)window level =0, window width =500 B)window level= +300, window width= 500
C)window level =+100, window width =1000 D)none of these - VERIFIED ANSWER✔✔-A) window level =0,
window width =500
What is the volume of a voxel if a slice thickness of 3 mm, a 512x512 matrix & a reconstruction field of view of
25.6cm are used A) 0.75mm³ B)1.5mm³ C) 6.0mm³ D)none of these - VERIFIED ANSWER✔✔-A. Solve this by
finding the pixel size first FOV/matrix size ... that is 0.5 ... now square that 0.25 .... multiply that by slice
thickness and you get 0.75
Which of the following parameters is responsible for partial volume averaging: A) matrix size B) kVp C)slice
thickness D) patient dose - VERIFIED ANSWER✔✔-C
Voxel equation - VERIFIED ANSWER✔✔-pixel area x section thickness
What is interpolation? - VERIFIED ANSWER✔✔-Mathematical method for taking SPIRAL data and viewing it
as AXIAL images
Bone windows - VERIFIED ANSWER✔✔-2000-4000 WW
200-400 WL
Lung windows - VERIFIED ANSWER✔✔-1400-1600 WW
(-)400-600 WL
Modular Transfer Function? - VERIFIED ANSWER✔✔-graphical representation of SPATIAL RESOLUTION
measured in lp/cm, tells how small you can scan without blurring
Decrease partial volume averaging? - VERIFIED ANSWER✔✔-Reduce slice thickness
Which portion of the pancreas is the most common site for tumors?; and where located? - VERIFIED
ANSWER✔✔-The head of the pancreas. It is located approximately at T12
LUNG WINDOW
(-) IS AIR - VERIFIED ANSWER✔✔-2000 WW and -200 WL =
The Hounsfield unit that is -1000 most likely represents which of the following? - VERIFIED ANSWER✔✔-Air
Relative to CT topography, slice thickness is best represented by which of the following axes? - VERIFIED
ANSWER✔✔-Z axis
What unit is the basis for exposure based on ionization in air? - VERIFIED ANSWER✔✔-mR or C/kg
What radiation unit considers the biological effectiveness of radiation exposure? - VERIFIED ANSWER✔✔-
mrem or mSv
"Fan" beam technology first historically came on the scene with which acquisition geometries? - VERIFIED
ANSWER✔✔-Second
"Rotate-rotate" applies to which of the following geometries? - VERIFIED ANSWER✔✔-Third
In CT what imaging plane is the pituitary best visualized? - VERIFIED ANSWER✔✔-coronal
The third ventricle of the brain communicates with the fourth ventricle through the - VERIFIED ANSWER✔✔-
Cerebral aqueduct
refers to an excessive Amount of nitrogenous materials in the blood and is a symptom of renal failure. -
VERIFIED ANSWER✔✔-Azotemia
, Which paranasal sinus is usually the last to fully develop? - VERIFIED ANSWER✔✔-Frontal
What is the average annual radiation dose? - VERIFIED ANSWER✔✔-2 rem
10 rem converted to Sieverts is what? - VERIFIED ANSWER✔✔-0.1 Sv
convert 10 mSv to Sv - VERIFIED ANSWER✔✔-0.01 sV
annual limit for adult occupational effective dose? - VERIFIED ANSWER✔✔-0.05 Sv
annual limit of occupational lens dose - VERIFIED ANSWER✔✔-0.15 Sv
annual limit of shallow dose equivalent to skin/extremities - VERIFIED ANSWER✔✔-0.5 Sv
occupational exposure to embryo/fetus during pregnancy - VERIFIED ANSWER✔✔-0.5 mSv
total effective dose equivalent to public
--also average background radiation - VERIFIED ANSWER✔✔-1 mSv
Mild reactions to iodinated intravenous contrast media include - VERIFIED ANSWER✔✔-nausea, vomiting,
mild urticaria, and a warm flushed sensation
Moderate reactions? - VERIFIED ANSWER✔✔-Dyspnea, Hives (urticarial); wheezing (mild bronchospasm);
change in pulse; facial edema; vasovagal response; hypo- or hypertension
Severe reactions? - VERIFIED ANSWER✔✔-Severe bronchospasm; anaphylaxis; Drowsiness; headache;
fever/chills, Shock, pulmonary edema
Osmolality - VERIFIED ANSWER✔✔-Concentration of a solution in terms of number of dissolved particles per
unit of water
Non-ionic intravenous contrast media such as Omnipaque should have an average osmolality of - VERIFIED
ANSWER✔✔-750 mOsm/kg water
What drugs are administered for moderate reaction to injection of iodinated contrast medium - VERIFIED
ANSWER✔✔-Antihistamines
Epinephrine
Prothrombin measures the amount of time necessary for a person's blood to coagulate - VERIFIED
ANSWER✔✔-normal limits: between 10 and 14 seconds
why use an autoclave? - VERIFIED ANSWER✔✔-The use of an autoclave for sterilization involves heat and
steam under pressure to eliminate microbes.
1 rem= 1 rad - VERIFIED ANSWER✔✔-When measuring the radiation dose from x-rays, rads and rems are
equivalent. The units of Sv and rem are used to measure any kind of ionizing radiation where 1 Sv =100rem. The
units of rad and Gy are used to measure specifically x-ray radiation where 1 Gy = 100 rads.
When performing a multi-slice CT study, the slice thickness may be ___________ to cover the region of interest,
in order to minimize the dose to the patient. - VERIFIED ANSWER✔✔-Due to radiation penumbra, a multiple
slice study results in a greater patient dose than the same number of individual slices. By covering a specific
region of interest with fewer slices (increase in slice thickness) the resulting radiation overlap from adjacent slices
is reduced, reducing the dose to the patient.
A given CT exam yields a CTDI of 4.5 rads, with a slice thickness of 10mm, and a 2mm gap between slices, the
MSAD for this exam is ________ rads. - VERIFIED ANSWER✔✔-The MSAD is equal to the CTDI X the ratio
of the slice thickness to the table increment. With a 2mm gap and a 10mm slice the table increment will be 12mm.
The MSAD = (4.5 rads) X (10mm/12mm)
