CT TEST REVIEW TEST QS AND AS FOR CT

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.)

Which is NOT a synonym for the preliminary/localizer image taken at the start of a CT examination?

• Topogram
• Scout
• Scanogram
• Spiral - Correct Answer D. Spiral

The ability of a system to differentiate, on the image, objects with similar densities is known as:

• High contrast resolution
• Low contrast resolution
• Spatial resolution
• Temporal resolution - Correct Answer B. Low contrast resolution

Each two dimensional square of data that make up the CT image is called a:

• Pixel
• Voxel
• Matrix
• Fragment - Correct Answer A. Pixel

How many pixels are contained in a 1,024 matrix image? A. 1,024

B. 2,048

C. 262,144

• 1,048,576 - Correct Answer D. 1,048,576

Beam attenuation can be defined as:

• The phenomenon by which artifacts result when lower energy photons are preferentially

absorbed, leaving only higher-intensity photons to strike the detector array. 1 / 4

• Xray energy that is produced from bombarding a substance with fast moving electrons.
• The ability of the detector to capture transmitted photons and change them to electronic signals.
• The phenomenon by which an xray beam passing through a structure is decreased in intensity or

amount because of absorption and interaction with matter. - Correct 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.

Which of the following is a low attenuation structure:

• Iodine filled aorta
• Rib
• Trachea
• Calcified arteries - Correct Answer C. Trachea

An object is slightly less dense than water. What is the expected hounsfield measurement?

A. -940

B. -10

• 50
• 850 - Correct Answer B. -10

Why does the administration of iodinated contrast media result in an enhanced image?

• Iodinated contrast material increases the ability of the enhanced structure to attenuate the xray

beam.

• Iodinated contrast material decreases the average photon energy of the xray beam; therefore

more photons are absorbed by the patient.

• The administration of contrast material results in a smaller pixel, thereby increasing spatial

resolution, which results in an enhanced image.

• - Correct 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:

• When viewed by the naked eye, the beam exhibits many different colors.
• It produce, as a byproduct, a substance known as polychlorinated biphenyl.
• Photons contained in the beam are all of the same wavelength. 2 / 4

• The beam comprises photons with varying energies. - Correct 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:

• Artifact
• Anomaly
• Shadow
• Ghost - Correct Answer A. Artifact

Which is an advantage of filtering the xray beam?

• Filtering reduces the anode heat load
• A filtered beam produces images with substantially less quantum mottle
• Filtering the beam prevents energy from being converted to heat, therefore 100% of the energy is

converted to xrays.

• Filtering reduces the radiation dose to the patient. - Correct Answer D. Filtering reduces the

radiation dose to the patient

Scan thickness is primarily important for the part it plays in:

• Noise reduction
• The contrast scale
• Detector aperture opening
• Volume averaging - Correct Answer D. 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?

• 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.

• 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.

• 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. 3 / 4

• The thickest slice available should be used to reduce the radiation dose to the corneas. - Correct

Answer 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.How many CT numbers are assigned to each pixel in the image matrix?

• One half the number of all values recorded from the detector array
• One
• The number of HU per pixel is one tenth the display field of view
• Two values for a 256 matrix; 4 values for a 512 matrix - Correct Answer B. One

Which is another name for raw data?

• Image data
• Scan data
• Reconstructed data
• Displayed data - Correct Answer B. Scan data

When in the anatomic position, the arms are:

• raised above the head, palms backwards
• crossed over the chest, palms on opposite shoulders
• down by the sides, palms forward
• by the sides, elbows bent, palms backward and resting on hips - Correct Answer C. down by the

sides, palms forward Which of the following components is NOT housed within the gantry?

• Three phase generator
• High-frequency generator
• Slip rings
• Xenon gas detectors - Correct Answer A. Three phase generator

The power capacity of the generator is listed in:

• milliamperes (mA)
• thousand heat units (KHU)
• / 4