CT TEST REVIEW (TEST Q'S AND A'S FOR CT REGISTRY PREP.
THIS IS FROM THE BOOK "COMPUTED TOMOGRAPHY FOR
TECHNOLOGISTS: EXAM REVIEW" BY LOIS E ROMANS.
PUBLISHED BY WOLTERS KLUWER, LIPPINCOTT WILLIAMS
AND WILKINS.) QUESTIONS & ANSWERS RATED 100%
On a CT image an ROI is placed within a structure and measured. Its standard
deviation is 0. What can be determined about this structure?
A. it is composed of water or something with the same density as water.
B. it is composed of fat
C. it is very homogenous
D. it is very heterogeneous - ANSWER -C. it is very homogenous
For which application are the raw data necessary?
A. to magnify the image
B. to decrease the display field size
C. to create a histogram
D. to obtain a hounsfield measurement of a specific structure - ANSWER -B. to
decrease the display field size
A magnification factor of 1.5 is used to enlarge the image data, resulting in:
A. a decrease in the pixel size
B. an increase in the pixel size
C. an inaccuracy in any subsequent distance measurement
D. an image that is larger and may allow a more accurate cursor placement for
measurements - ANSWER -D. an image that is larger and may allow a more
accurate cursor placement for measurements
Compared with conventional radiographic images, CT localizer images:
A. do not superimpose anatomic structures
B. are of slightly poorer image quality
c. result in a much higher radiation dose to the patient
d. result in a much lower radiation dose to the patient - ANSWER -B. are of
slightly poorer image quality
Which are key aspects of the axial method of data acquisition?
A. the table remains stationary while the xray tube rotates within the gantry,
collecting data
,B. multiple parallel rows of detectors are needed
C. the table moves continuously throughout the data acquisition
D. each slice is created from data acquired during a 180 degree rotation of the tube
- ANSWER -A. the table remains stationary while the xray tube rotates within the
gantry, collecting data
The interscan delay inherent in an axial scan method is caused by which factor?
A. tube cooling
B. detector realignment
C. table movement between data acquisitions
D. serial image reconstruction algorithms that must reconstruct data from each
slice before data for the next slice can be acquired - ANSWER -C. table movement
between data acquisitions
The practice of grouping more than one axial scan in a single breath hold is often
referred to as:
A. reformatting
B. clustering
C. dynamic scanning
D. volumetric scanning - ANSWER -B. clustering
Compared with helical scanning, what are the primary dis-advantages to the axial
method of scanning?
A. low contrast resolution is inferior
B. spatial resolution is inferior
C. radiation dose is much higher; noise is more pronounced
D. total examination time is longer; data reconstruction is more limited - ANSWER
-D. total examination time is longer, data reconstruction is more limited
What is it called when a patient breathes differently with each data acquisition and
areas of anatomy seem to be misplaced in the z-axis?
A. mis-registration
B. retrospective reconstruction
C. slice thickness blooming
D. slice sensitivity profile degradation - ANSWER -A. mis-registration
Basic ingredients defining a helical scan include all of the following except:
A. a continually rotating xray tube
B. multiple parallel rows of detectors
C. constant xray output
,D. uninterrupted table movement - ANSWER -B. multiple parallel rows of
detectors
All of the following are synonyms for helical scanning except:
A. volumetric scanning
B. spiral scanning
C. continuous acquisition scanning
D. dynamic scanning - ANSWER -D. dynamic scanning
All of the following were improvements necessary to make helical scanning
possible except:
A. fourth generation scanner design
B. gantries with slip ring design
C. software the adjusts for table motion
D. improved raw data management - ANSWER -A. fourth generation scanner
design
The goal of helical interpolation methods is to:
A. calculate the appropriate mAs for a given patient size
B. take the slant and the blur out of the helical image so that they closely resemble
images taken from the axial methods
C. automatically assign the optimal window width and level to each reconstructed
image
D. eliminate artifacts from voluntary and involuntary patient motion - ANSWER -
B. take the slant and the blur out of the helical image so that they closely resemble
images taken from the axial methods
What is the pitch in the following scenario: 16 slice scanner, .5mm slice thickness,
table movement of 12mm per rotation.
A. 1
B. 1.25
C. 1.5
D. 2 - ANSWER -C. 1.5
How much anatomy (lengthwise) will be covered in a helical scan when the
following parameters are selected: 15 seconds total acquisition time, .5 seconds
gantry rotation time, 2mm slice thickness, 4 slices per rotation , pitch of 1.5?
A. 40mm
B. 90mm
C. 160mm
, D. 360mm - ANSWER -D. 360mm
Which of the following is NOT a reconstruction possibility when an MDCT
system produces four 1mm slices with each gantry rotation?
A. slices can be combined to create two/2mm slices
B. slices can be combined to create one/4mm slice
C. slices can be divided to produce 16/.25mm slices
D. slices can be reconstructed to create images that overlap by .5mm - ANSWER -
C. slices can be divided to produce 16/.25 mm slices
All of the following are scan parameters EXCEPT:
A. mAs
B. slice thickness
C. matrix
D. pitch - ANSWER -C. Matrix
Which of the following combinations of mA and scan time will result in 350 mAs
and be the best choice for a cardiac scan?
A. mA=300, scan time=.50 seconds
B. mA=200, scan time=2 seconds
C. mA=350, scan time=1 second
D. mA=700, scan time=.50 seconds - ANSWER -D. mA=700, scan time=.50
seconds
Which can be attributed to the uncoupling effect?
A. Even when the mAs or kVp are too high, a good image results
B. When mAs or kVp settings are too high or too low, quantum mottle results
C. mA and scan time have no relationship to the quantity of xray produced
D. Normal xray physics are reversed; mAs controls the quality of the xray beam,
whereas the kVp controls the quantity of the xray beam - ANSWER -A. Even
when the mAs or kVp are too high, a good image results
Which is a disadvantage of a bone algorithm?
A. it reduces spatial resolution
B. it smooths data, reducing the difference between adjacent pixels
C. it accentuates the difference between neighboring pixels
D. it reduces the visibility of soft tissue structures - ANSWER -D. it reduces the
visibility of soft tissue structures
What is a partial scan?
THIS IS FROM THE BOOK "COMPUTED TOMOGRAPHY FOR
TECHNOLOGISTS: EXAM REVIEW" BY LOIS E ROMANS.
PUBLISHED BY WOLTERS KLUWER, LIPPINCOTT WILLIAMS
AND WILKINS.) QUESTIONS & ANSWERS RATED 100%
On a CT image an ROI is placed within a structure and measured. Its standard
deviation is 0. What can be determined about this structure?
A. it is composed of water or something with the same density as water.
B. it is composed of fat
C. it is very homogenous
D. it is very heterogeneous - ANSWER -C. it is very homogenous
For which application are the raw data necessary?
A. to magnify the image
B. to decrease the display field size
C. to create a histogram
D. to obtain a hounsfield measurement of a specific structure - ANSWER -B. to
decrease the display field size
A magnification factor of 1.5 is used to enlarge the image data, resulting in:
A. a decrease in the pixel size
B. an increase in the pixel size
C. an inaccuracy in any subsequent distance measurement
D. an image that is larger and may allow a more accurate cursor placement for
measurements - ANSWER -D. an image that is larger and may allow a more
accurate cursor placement for measurements
Compared with conventional radiographic images, CT localizer images:
A. do not superimpose anatomic structures
B. are of slightly poorer image quality
c. result in a much higher radiation dose to the patient
d. result in a much lower radiation dose to the patient - ANSWER -B. are of
slightly poorer image quality
Which are key aspects of the axial method of data acquisition?
A. the table remains stationary while the xray tube rotates within the gantry,
collecting data
,B. multiple parallel rows of detectors are needed
C. the table moves continuously throughout the data acquisition
D. each slice is created from data acquired during a 180 degree rotation of the tube
- ANSWER -A. the table remains stationary while the xray tube rotates within the
gantry, collecting data
The interscan delay inherent in an axial scan method is caused by which factor?
A. tube cooling
B. detector realignment
C. table movement between data acquisitions
D. serial image reconstruction algorithms that must reconstruct data from each
slice before data for the next slice can be acquired - ANSWER -C. table movement
between data acquisitions
The practice of grouping more than one axial scan in a single breath hold is often
referred to as:
A. reformatting
B. clustering
C. dynamic scanning
D. volumetric scanning - ANSWER -B. clustering
Compared with helical scanning, what are the primary dis-advantages to the axial
method of scanning?
A. low contrast resolution is inferior
B. spatial resolution is inferior
C. radiation dose is much higher; noise is more pronounced
D. total examination time is longer; data reconstruction is more limited - ANSWER
-D. total examination time is longer, data reconstruction is more limited
What is it called when a patient breathes differently with each data acquisition and
areas of anatomy seem to be misplaced in the z-axis?
A. mis-registration
B. retrospective reconstruction
C. slice thickness blooming
D. slice sensitivity profile degradation - ANSWER -A. mis-registration
Basic ingredients defining a helical scan include all of the following except:
A. a continually rotating xray tube
B. multiple parallel rows of detectors
C. constant xray output
,D. uninterrupted table movement - ANSWER -B. multiple parallel rows of
detectors
All of the following are synonyms for helical scanning except:
A. volumetric scanning
B. spiral scanning
C. continuous acquisition scanning
D. dynamic scanning - ANSWER -D. dynamic scanning
All of the following were improvements necessary to make helical scanning
possible except:
A. fourth generation scanner design
B. gantries with slip ring design
C. software the adjusts for table motion
D. improved raw data management - ANSWER -A. fourth generation scanner
design
The goal of helical interpolation methods is to:
A. calculate the appropriate mAs for a given patient size
B. take the slant and the blur out of the helical image so that they closely resemble
images taken from the axial methods
C. automatically assign the optimal window width and level to each reconstructed
image
D. eliminate artifacts from voluntary and involuntary patient motion - ANSWER -
B. take the slant and the blur out of the helical image so that they closely resemble
images taken from the axial methods
What is the pitch in the following scenario: 16 slice scanner, .5mm slice thickness,
table movement of 12mm per rotation.
A. 1
B. 1.25
C. 1.5
D. 2 - ANSWER -C. 1.5
How much anatomy (lengthwise) will be covered in a helical scan when the
following parameters are selected: 15 seconds total acquisition time, .5 seconds
gantry rotation time, 2mm slice thickness, 4 slices per rotation , pitch of 1.5?
A. 40mm
B. 90mm
C. 160mm
, D. 360mm - ANSWER -D. 360mm
Which of the following is NOT a reconstruction possibility when an MDCT
system produces four 1mm slices with each gantry rotation?
A. slices can be combined to create two/2mm slices
B. slices can be combined to create one/4mm slice
C. slices can be divided to produce 16/.25mm slices
D. slices can be reconstructed to create images that overlap by .5mm - ANSWER -
C. slices can be divided to produce 16/.25 mm slices
All of the following are scan parameters EXCEPT:
A. mAs
B. slice thickness
C. matrix
D. pitch - ANSWER -C. Matrix
Which of the following combinations of mA and scan time will result in 350 mAs
and be the best choice for a cardiac scan?
A. mA=300, scan time=.50 seconds
B. mA=200, scan time=2 seconds
C. mA=350, scan time=1 second
D. mA=700, scan time=.50 seconds - ANSWER -D. mA=700, scan time=.50
seconds
Which can be attributed to the uncoupling effect?
A. Even when the mAs or kVp are too high, a good image results
B. When mAs or kVp settings are too high or too low, quantum mottle results
C. mA and scan time have no relationship to the quantity of xray produced
D. Normal xray physics are reversed; mAs controls the quality of the xray beam,
whereas the kVp controls the quantity of the xray beam - ANSWER -A. Even
when the mAs or kVp are too high, a good image results
Which is a disadvantage of a bone algorithm?
A. it reduces spatial resolution
B. it smooths data, reducing the difference between adjacent pixels
C. it accentuates the difference between neighboring pixels
D. it reduces the visibility of soft tissue structures - ANSWER -D. it reduces the
visibility of soft tissue structures
What is a partial scan?
