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CT Test review QuestionsWhich 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 - answerD. 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 - answerB. 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 - answerA. 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 - answerD. 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. - answerD.
The phenomenon by which an xray beam passing through a structure is decreased in
intensity or amount because of absorption and interaction with matter.
Which of the following is a low attenuation structure:
A. Iodine filled aorta
,B. Rib
C. Trachea
D. Calcified arteries - answerC. Trachea
An object is slightly less dense than water. What is the expected hounsfield
measurement?
A. -940
B. -10
C. 50
D. 850 - answerB. -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. - answerA. 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. - answerD. 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 - answerA. Artifact
Which is an advantage of filtering the xray beam?
A. Filtering reduces the anode heat load
B. A filtered beam produces images with substantially less quantum mottle
C. Filtering the beam prevents energy from being converted to heat, therefore 100% of
the energy is converted to xrays.
D. Filtering reduces the radiation dose to the patient. - answerD. Filtering reduces the
radiation dose to the patient
Scan thickness is primarily important for the part it plays in:
A. Noise reduction
B. The contrast scale
,C. Detector aperture opening
D. Volume averaging - answerD. Volume averaging
You are working with the radiologist to establish examination protocols for your
department. Which of the following is a logical consideration when determining an
appropriate slice thickness for studies of the internal auditory canal?
A. Because the auditory ossicles are quite small, a thin slice will be necessary to reduce
the chance that volume averaging will obscure their appearance on the image.
B. The appropriate slice thickness will vary considerably from patient to patient.
Therefore, each technologist should be free to adjust the slice thickness as he or she
deems necessary for the particular patient.
C. A slice thickness of 5 to 7mm is adequate because the structures of interest are not
particularly small and the examination is most often ordered as a screening study for
asymptomatic patients.
D. The thickest slice available should be used to reduce the radiation dose to the
corneas. - answerA. Because the auditory ossicles are quite small, a thin slice will be
necessary to reduce the chance that volume averaging will obscure their appearance on
the image.
How many CT numbers are assigned to each pixel in the image matrix?
A. One half the number of all values recorded from the detector array
B. One
C. The number of HU per pixel is one tenth the display field of view
D. Two values for a 256 matrix; 4 values for a 512 matrix - answerB. One
Which is another name for raw data?
A. Image data
B. Scan data
C. Reconstructed data
D. Displayed data - answerB. Scan data
When in the anatomic position, the arms are:
A. raised above the head, palms backwards
B. crossed over the chest, palms on opposite shoulders
C. down by the sides, palms forward
D. by the sides, elbows bent, palms backward and resting on hips - answerC. down by
the sides, palms forward
Which of the following components is NOT housed within the gantry?
A. Three phase generator
B. High-frequency generator
C. Slip rings
D. Xenon gas detectors - answerA. Three phase generator
The power capacity of the generator is listed in:
A. milliamperes (mA)
, B. thousand heat units (KHU)
C. million heat units (MHU)
D. kilowatts (kW) - answerD. kilowatts (kW)
Which of the following describes a slip ring device?
A. A recoiling system cable used to rotate the gantry frame
B. A brushlike apparatus that provides continuous electrical power and electronic
communication across a rotating surface
C. A device used to shape the xray beam, thereby reducing the radiation dose to the
patient and reducing image artifact
D. A device that restricts the xray beam emerging from the gantry to thin ribbons -
answerB. A brushlike apparatus that provides continuous electrical power and electronic
communication across a rotating surface
Which is a disadvantage of a small focal spot size?
A. Reduced spatial resolution
B. Reduced detector efficiency
C. Increased penumbra
D. Reduced heat capacity - answerD. Reduced heat capacity
The ability of the tube to withstand by product heat is called:
A. heat capacity
B. heat dissipation
C. thermal potential
D. thermal transference - answerA. Heat capacity
Regarding the detectors in the CT system, geometric efficiency is controlled primarily
by:
A. detector material
B. type of photodiode used
C. filtration
D. detector spacing and aperture - answerD. Detector spacing and aperture
Which of the following is a characteristic of xenon gas detectors?
A. Low efficiency
B. Sensitive to temperature and moisture
C. May exhibit afterglow
D. Also called scintillators - answerA. Low efficiency
Which component of the CT system converts the electric signal supplied by the
detectors into a digital format?
A. Photodiode
B. Array processor
C. Display processor
D. Analog to digital converter - answerD. Analog to digital converter
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