Computed Tomography for Technologists 2nd Edition
Exam Review with questions and 100 %all sure answers
2024
Which is NOT a synonym for the preliminary/localizer image taken at the start of a CT examination?
A. Topogram
B. Scout
C. Scanogram
D. Spiral - Answer- D. Spiral
The ability of a system to differentiate, on the image, objects with similar densities is known as:
A. High contrast resolution
B. Low contrast resolution
C. Spatial resolution
D. Temporal resolution - Answer- B. Low contrast resolution
Each two dimensional square of data that make up the CT image is called a:
A. Pixel
B. Voxel
C. Matrix
D. Fragment - Answer- A. Pixel
How many pixels are contained in a 1,024 matrix image? A. 1,024
B. 2,048
C. 262,144
D. 1,048,576 - Answer- D. 1,048,576
Beam attenuation can be defined as:
A. The phenomenon by which artifacts result when lower energy photons are preferentially absorbed,
leaving only higher-intensity photons to strike the detector array.
,B. Xray energy that is produced from bombarding a substance with fast moving electrons.
C. The ability of the detector to capture transmitted photons and change them to electronic signals.
D. The phenomenon by which an xray beam passing through a structure is decreased in intensity or
amount because of absorption and interaction with matter. - Answer- D. The phenomenon by which an
xray beam passing through a structure is decreased in intensity or amount because of absorption and
interaction with matter.
CT basics - Answer- • Essentially an x-ray tube that rotates round the pt
• Table moves, feeding pt into the gantry
• Each large is data collected as a series of slices
o Each slice is divided into voxels (volume elements)
Multislice scanner - Answer- voxel thickness is equal to x-ray beam thickness
Slices - Answer- o Thinner slice higher radiation dose better quality image
o Width and height depend on FOV
o Determined by the operator
o Thickness is determined by the image requirements
calculate linear attenuation coefficient for each voxel - Answer- o From this a T # is calculated this
determines hoe the voxel appears
o Voxel appearance can be changed with windowing
♣ High CT numbers: brighter
♣ Low CT numbers: darker
• Linear attenuation coefficient is calculated in the reconstruction process
Linear attenuation coefficient calculation - Answer- Xray tube passes around the pt, through the pt and
detected when they leave the pt
o By comparing their intensities to unattenuated rays, the net linear attenuation is calculated for each ray
o This # is assigned to each voxel along the rays path
o By doing this from a number of different angles the true values for each voxel is obtained
• Each voxel is assigned a CT # which depends on its linear attenuation coefficient
,o This is assigned a shade of gray for the final display
Which of the following is a low attenuation structure:
A. Iodine filled aorta
B. Rib
C. Trachea
D. Calcified arteries - Answer- C. Trachea
An object is slightly less dense than water. What is the expected hounsfield measurement?
A. -940
B. -10
C. 50
D. 850 - Answer- B. -10
Why does the administration of iodinated contrast media result in an enhanced image?
A. Iodinated contrast material increases the ability of the enhanced structure to attenuate the xray beam.
B. Iodinated contrast material decreases the average photon energy of the xray beam; therefore more
photons are absorbed by the patient.
C. The administration of contrast material results in a smaller pixel, thereby increasing spatial resolution,
which results in an enhanced image.
D. - Answer- A. Iodinated contrast material increases the ability of the enhanced structure to attenuate the
xray beam.
The xray beam sources for CT produce xray energy that is polychromatic. This means:
A. When viewed by the naked eye, the beam exhibits many different colors.
B. It produce, as a byproduct, a substance known as polychlorinated biphenyl.
C. Photons contained in the beam are all of the same wavelength.
D. The beam comprises photons with varying energies. - Answer- D. The beam comprises photons with
varying energies.
An object that appears on the image but is not present in the object scanned is called a/n:
, A. Artifact
B. Anomaly
C. Shadow
D. Ghost - Answer- A. Artifact
first generation CT - Answer- Translate-Rotate
xray beam picked up by single detector and move together, then rotate together to image a different angle.
5min/slice
second generation CT - Answer- Translate-Rotate
xray beam picked up by a row of up to 30 detectors and move together, then rotate together to image a
different angle. 5-90s/slice
third generation CT - Answer- Rotate-Rotate
xray beam hits a row of detector wide enough to image a whole slice, then they both rotate together to
image a different angle. >1s/slice
fourth generation - Answer- Rotate-Rotate
fixed complete ring of detectors and xray source rotates around to capture a slice. they both move down
the patient to begin imaging a new slice
EBCT (electron beam computed tomography) - Answer- uses large electron gun as stay source, used in
cardiac imaging
Localizer scans (scout, topogram) - Answer- digital image acquisitions that are created while the tube is
stationary and the table moves through the scan field
conventional method (serial) - Answer- when the xray tube rotates around the patients, while the table
moves in increments per slice to generate the CT image.
Helical Method (spiral, volumetric) - Answer- xray tube and table move simultaneously. Tube rotates
around the patients as table is fed through the gantry
Exam Review with questions and 100 %all sure answers
2024
Which is NOT a synonym for the preliminary/localizer image taken at the start of a CT examination?
A. Topogram
B. Scout
C. Scanogram
D. Spiral - Answer- D. Spiral
The ability of a system to differentiate, on the image, objects with similar densities is known as:
A. High contrast resolution
B. Low contrast resolution
C. Spatial resolution
D. Temporal resolution - Answer- B. Low contrast resolution
Each two dimensional square of data that make up the CT image is called a:
A. Pixel
B. Voxel
C. Matrix
D. Fragment - Answer- A. Pixel
How many pixels are contained in a 1,024 matrix image? A. 1,024
B. 2,048
C. 262,144
D. 1,048,576 - Answer- D. 1,048,576
Beam attenuation can be defined as:
A. The phenomenon by which artifacts result when lower energy photons are preferentially absorbed,
leaving only higher-intensity photons to strike the detector array.
,B. Xray energy that is produced from bombarding a substance with fast moving electrons.
C. The ability of the detector to capture transmitted photons and change them to electronic signals.
D. The phenomenon by which an xray beam passing through a structure is decreased in intensity or
amount because of absorption and interaction with matter. - Answer- D. The phenomenon by which an
xray beam passing through a structure is decreased in intensity or amount because of absorption and
interaction with matter.
CT basics - Answer- • Essentially an x-ray tube that rotates round the pt
• Table moves, feeding pt into the gantry
• Each large is data collected as a series of slices
o Each slice is divided into voxels (volume elements)
Multislice scanner - Answer- voxel thickness is equal to x-ray beam thickness
Slices - Answer- o Thinner slice higher radiation dose better quality image
o Width and height depend on FOV
o Determined by the operator
o Thickness is determined by the image requirements
calculate linear attenuation coefficient for each voxel - Answer- o From this a T # is calculated this
determines hoe the voxel appears
o Voxel appearance can be changed with windowing
♣ High CT numbers: brighter
♣ Low CT numbers: darker
• Linear attenuation coefficient is calculated in the reconstruction process
Linear attenuation coefficient calculation - Answer- Xray tube passes around the pt, through the pt and
detected when they leave the pt
o By comparing their intensities to unattenuated rays, the net linear attenuation is calculated for each ray
o This # is assigned to each voxel along the rays path
o By doing this from a number of different angles the true values for each voxel is obtained
• Each voxel is assigned a CT # which depends on its linear attenuation coefficient
,o This is assigned a shade of gray for the final display
Which of the following is a low attenuation structure:
A. Iodine filled aorta
B. Rib
C. Trachea
D. Calcified arteries - Answer- C. Trachea
An object is slightly less dense than water. What is the expected hounsfield measurement?
A. -940
B. -10
C. 50
D. 850 - Answer- B. -10
Why does the administration of iodinated contrast media result in an enhanced image?
A. Iodinated contrast material increases the ability of the enhanced structure to attenuate the xray beam.
B. Iodinated contrast material decreases the average photon energy of the xray beam; therefore more
photons are absorbed by the patient.
C. The administration of contrast material results in a smaller pixel, thereby increasing spatial resolution,
which results in an enhanced image.
D. - Answer- A. Iodinated contrast material increases the ability of the enhanced structure to attenuate the
xray beam.
The xray beam sources for CT produce xray energy that is polychromatic. This means:
A. When viewed by the naked eye, the beam exhibits many different colors.
B. It produce, as a byproduct, a substance known as polychlorinated biphenyl.
C. Photons contained in the beam are all of the same wavelength.
D. The beam comprises photons with varying energies. - Answer- D. The beam comprises photons with
varying energies.
An object that appears on the image but is not present in the object scanned is called a/n:
, A. Artifact
B. Anomaly
C. Shadow
D. Ghost - Answer- A. Artifact
first generation CT - Answer- Translate-Rotate
xray beam picked up by single detector and move together, then rotate together to image a different angle.
5min/slice
second generation CT - Answer- Translate-Rotate
xray beam picked up by a row of up to 30 detectors and move together, then rotate together to image a
different angle. 5-90s/slice
third generation CT - Answer- Rotate-Rotate
xray beam hits a row of detector wide enough to image a whole slice, then they both rotate together to
image a different angle. >1s/slice
fourth generation - Answer- Rotate-Rotate
fixed complete ring of detectors and xray source rotates around to capture a slice. they both move down
the patient to begin imaging a new slice
EBCT (electron beam computed tomography) - Answer- uses large electron gun as stay source, used in
cardiac imaging
Localizer scans (scout, topogram) - Answer- digital image acquisitions that are created while the tube is
stationary and the table moves through the scan field
conventional method (serial) - Answer- when the xray tube rotates around the patients, while the table
moves in increments per slice to generate the CT image.
Helical Method (spiral, volumetric) - Answer- xray tube and table move simultaneously. Tube rotates
around the patients as table is fed through the gantry
