CT REGISTRY- STUDY THIS AND YOU'LL PASS!! (excluding anatomy) Questions With 100% Verified Answers A+GRADED
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CT REGISTRY
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CT REGISTRY
CT REGISTRY- STUDY THIS AND YOU'LL PASS!! (excluding anatomy) Questions With 100% Verified Answers A+GRADED
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 bif...
CT REGISTRY- STUDY THIS AND YOU'LL
PASS!! (excluding anatomy) Questions
With 100% Verified Answers A+GRADED
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
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
AGRADESOLUTIONS
,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.
- 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 - 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
5) reconstruction algorthith - soft tissue>bone
Give window levels for brain, lung, abdomen, bone - correct answer...✔✔Brain:
W80,L+40
Lung: W1500, L-400
Abdomen: W400, L+50
Bone: W1600, L+500
AGRADESOLUTIONS
,What is beam hardening?
what are the two types of beam hardening artifact?
how do you compensate for it? - correct 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 - correct 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? - correct 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
- correct 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 - correct 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 - correct 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 - correct answer...✔✔C
Voxel equation - correct answer...✔✔pixel area x section thickness
AGRADESOLUTIONS
, What is interpolation? - correct answer...✔✔Mathematical method for taking SPIRAL
data and viewing it as AXIAL images
Bone windows - correct answer...✔✔2000-4000 WW
200-400 WL
Lung windows - correct answer...✔✔1400-1600 WW
(-)400-600 WL
Modular Transfer Function? - correct answer...✔✔graphical representation of SPATIAL
RESOLUTION measured in lp/cm, tells how small you can scan without blurring
Which portion of the pancreas is the most common site for tumors?; and where located?
- correct answer...✔✔The head of the pancreas. It is located approximately at T12
LUNG WINDOW
(-) IS AIR - correct answer...✔✔2000 WW and -200 WL =
The Hounsfield unit that is -1000 most likely represents which of the following? - correct
answer...✔✔Air
Relative to CT topography, slice thickness is best represented by which of the following
axes? - correct answer...✔✔Z axis
What unit is the basis for exposure based on ionization in air? - correct answer...✔✔
mR or C/kg
What radiation unit considers the biological effectiveness of radiation exposure? -
correct answer...✔✔mrem or mSv
"Fan" beam technology first historically came on the scene with which acquisition
geometries? - correct answer...✔✔Second
"Rotate-rotate" applies to which of the following geometries? - correct answer...✔✔
Third
In CT what imaging plane is the pituitary best visualized? - correct answer...✔✔coronal
The third ventricle of the brain communicates with the fourth ventricle through the -
correct answer...✔✔Cerebral aqueduct
AGRADESOLUTIONS
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