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Flashcards in Midterm Review Deck (71)
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1

Scan thickness is primarily important for the part it plays in

Volume averaging

2

What is an imaging challenge that depends on contrast resolution?

Distinguishing between the white and grey matter of the brain

3

The ability of the tube to withstand by-product heat is called?
A) heat capacity
B) heat dissipation
C) thermal potential
D) thermal transference

A) heat capacity

4

Which of the following describes a slip ring device?
A) a recoiling system cable used to rotate the gantry frame
B) a brush like apparatus that provides continuous electrical power and electronic communication across a rotating surface
C) a device used to shape the x-ray beam, thereby reducing the radiation dose to the patient and reducing image artifact (beam hardening
D) a device that restricts the x-ray beam emerging from the gantry to thin ribbons

B) a brush like apparatus that provides continuous electrical power and electronic communication across a rotating surface

5

Which of the following is a TRUE statement regarding MPR's?
A) they are created from raw data
B) they are 3D in nature
C) all MPR images have the same image quality as the source image
D) they can be created either at the operators console or at a separate workstation

D) they can be created either at the operators console or at a separate workstation

6

Basic ingredients defining helical scan include all of the following EXCEPT:
A) a continually rotating x-ray tube
B) only multiple parallel rows of detectors
C) constant x-ray output
D) uninterrupted table movement

B) only multiple parallel rows of detectors

7

Each two dimensional square of data that make up the CT image is called a:
A) pixel
B) voxel
C) matrix
D) HU

A) pixel

8

Which is an advantage or filtering the x-ray beam?
A) filtering reduces 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 x-rays
D) filtering reduces the radiation dose to the patient

D) filtering reduces the radiation dose to the patient

9

The DAS reads each arriving ray and measures how much of the beam has been attenuated. This is:
A) a ray sum
B) a view
C) back projection
D) a sample

A) A ray sum

10

Which is a disadvantage of workstation created MPRs
A) they require that the raw data be sent to the workstation, which is difficult to transmit via the PACS
B) to produce the highest quality MPRs the thinnest slices must be sent to the PACS workstation. This amount of data can slow down the PACS
C) most radiologists have not been trained to create MPRs
D) workstations are only able to create MPRs in sagittal and coronal planes

B) to produce the highest quality MPRs the thinnest slices must be sent to the workstation. This amount of data can slow down the PACS

11

Which component of the CT system converts the electric signal supplied by the detectors into a digital format?
A) photodiode
B) array processor
C) DAC
D) ADC

D) ADC

12

In what situation would overlapping reconstructions for subsequent image rendering not be indicated?
A) slice thickness = 0.5mm, DFOV = 25
B) slice thickness = 2mm, DFOV = 35
C) slice thickness = 5mm, DFOV = 42
D) slice thickness = 7mm, DFOV = 45

A) slice thickness = 0.5mm, DFOV = 25

13

All of the following are synonyms for helical scanning EXCEPT:
A) volumetric scanning
B) spiral scanning
C) continuos acquisition scanning
D) dynamic scanning

D) dynamic scanning

14

What two main features are assessed to measure the image quality?
A) mAs and kVp
B) spatial and contrast resolution
C) temporal resolution and the degree of motion artifact
D) focal spot size and DFOV

B) spatial and contrast resolution

15

VR techniques assign each voxel an opacity value based on its ____. This value determines the degree the voxel will contribute to the final image
A) location
B) HU
C) depth
D) width

B) HU

16

When in the anatomic position, the arms are:
A) raised above the head, palms facing backward
B) crossed over the best, palms on opposite shoulders
C) down by the sides, palms facing forward
D) by the sides, with the elbows bent, palms facing backward and resting on the hips

C) down by the sides, palms facing forward

17

Regarding the detectors in the CT system, geometric efficiency is controlled primarily by?
A) detector material (solid state crystals or xenon gas chambers)
B) type of photodiode used
C) filtration
D) detector spacing and aperture

D) detector spacing and aperature

18

The x-ray beam sources for CT produce x-ray energy that is polychromatic. This means that:
A) when viewed by the naked eye, the beam exhibits many different colours
B) it produces, 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

D) the beam comprises photons with varying energies

19

Which of the following is a higher attenuation structure?
A) esophagus
B) liver
C) barium filled bowel
D) spine

C) barium filled bowel

20

All of the following were improvements necessary to make helical scanning possible EXCEPT:
A) 4th generation scanner design
B) gantries with slip ring designs
C) software that adjusts for table motion
D) improved raw data management

A) 4th generation scanner design

21

You are working with the radiologists to establish examination protocols for your department. What 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

22

What HU values are in the naturally occurring range (not man made object like surgical clips)?
A) -1000 to 1000
B) -600 to 0
C) 0 to 1200
D) -2000 to 4000

A) -1000 to 1000

23

Increasing the SFOV
A) increases the number of detector cells collecting data
B) increases the range of HU displayed on the image
C) decreases the pixel size
D) decreases the DFOV

A) increases the number of detector cells collecting data

24

Assume the raw data are still available. In what scenario would it be impossible to create an MPR?
A) source images vary in slice thickness
B) source images vary in gantry tilt
C) source images vary in image center
D) source images vary in DFOV

B) source images vary in gantry tilt

25

Raw data that results from a MDCT scan acquisition is used so that the 1mm slices are combines to produce thicker slices for viewing. This is called:
A) 3D reformatting
B) image reconstruction
C) segmentation
D) multiplanar reformation

B) image reconstruction

26

The DAS reads each arriving ray and measures how much of the beam has been attenuated. This is:
A) a ray sum
B) a view
C) back projection
D) a sample

A) a ray sum

27

All the thousands of bits of data acquired by the CT system with each scan are called:
A) image data
B) calibration detectors
C) raw data
D) ray sums

C) raw data

28

Which is NOT a synonym for the localizer image taken at the start of a CT examination?
A) topogram
B) scout
C) scanogram
D) spiral

D) spiral

29

Compared with helical scanning, what are the primary disadvantages 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 reformatting is more limited

D) total examination time is longer, data reformatting is more limited

30

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 from the next slice can be acquired

C) table movement between data acquisitions