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Flashcards in Midterm Review Deck (71):
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

31

What is the true test quality of a specific image?
A) whether it serves the purpose for which it is acquired
B) whether it has a limiting resolution for 7 lp/mm or greater
C) whether it has an MTF greater than 1
D) whether pixel size is 0.5mm or smaller

A) whether it serves the purpose for which it is acquired

32

Which are the key aspects of the axial method of data acquisition?
A) the table remains stationary while the x-ray 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 x-ray tube

A) the table remains stationary while the x-ray tube rotates within the gantry, collecting data

33

What is interpolation?
A) a technique for expressing waveform as a weighted sum of sines and cosines
B) an efficient algorithm used to compare DFT and its inverse
C) the difference between the first quartile and the third quartile. This is one way to describe the spread of a set of data
D) a mathematical method of estimating an unknown value using the known values on either side of the unknown

D) a mathematical method of estimating an unknown value using the known values on either side of the unknown

34

A term which describes an isotropic voxel
A) a rectangular solid
B) a square
C) a cube

C) a cube

35

What is a disadvantage of a bone algorithm?
A) it reduces spatial resolution
B) it smoothed data, reducing the difference between adjacent pixels
C) it accentuates difference between neighboring pixels
D) it reduces visibility of soft tissue structures

D) it reduces visibility of soft tissue structures

36

The process of converting the data from the attenuation profile to a matrix is known as:
A) reformation
B) archiving
C) back projection
D) referencing

C) back projection

37

The process of applying a filter function to an attenuation profile is known as:
A) data processing
B) convolution
C) archiving
D) reformation

B) convolution

38

Which of the following components is NOT housed within the gantry?
A) three-phase generator
B) slip rings
C) xenon gas detectors
D) filtration

A) three-phase generator

39

Which is a TRUE statement regarding beam hardening?
A) the beam is hardened more by bone and less by fat
B) the beam is hardened more by air and less by bone
C) nothing can be done to minimize beam hardening artifacts
D) lowering the kVp is the best method of reducing beam hardening artifacts

A) the beam is hardened more by bone and less by fat

40

An object that appears on the image but is not present in the object scanned is called a (an)
A) artifact
B) anomaly
C) shadow
D) streaking

A) artifact

41

Which can be attributed to the uncoupling effect?
A) even when mAs or kVp setting are too high, a good image results
B) when mA and scan time have no relationship to the quantity of x-rays produced
C) normal x-ray physics are reversed; mAs controls the quality of the x-ray beam, whereas kVp controls the quantity of the x-ray beam
D) when mAs or kVp setting are either too high or too low, quantum mottle results

A) even when mAs or kVp settings are too high, a good image results

42

Which of the following is a TRUE statement regarding MPRs?
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

43

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

B) are of slightly poorer image quality

44

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

D) volume averaging

45

A limitation of scanner- created MPRs is:
A) only one examination protocol per scanner can be programmed automatically to create MPRs
B) they take more time to create than manually produced MPRs
C) in most cases, only straight sagittal and coronal planes can be automatically generated
D) they are not consistently produced, so techs must remember to check to see whether they were created

C) in most cases, only straight sagittal and coronal planes can be automatically generated

46

Decreasing the window width in a CT image decreases:
A) slice thickness
B) mAs
C) the appearance of quantum mottle
D) the anatomic diversity displayed

D) the anatomic diversity displayed

47

Which has become the favored 3D imaging technique in CT?
A) volume rendering
B) surface rendering
C) MIP
D) MinIp

A) volume rendering

48

Why is it necessary to convert the digitized data from the reconstruction processor to shades of grey?
A) to allow a HU to be assigned to each structure
B) to remove streak artifacts from the final image
C) to enhance the desirable aspects of the image and suppress the undesirable aspects
D) so that the image can be displayed on a monitor

D) so that the image can be displayed on a monitor

49

For which application are the raw data necessary?
A) to magnify the image
B) to decrease DFOV
C) to create a histogram
D) to obtain a HU measurement of a specific structure

B) to decrease DFOV

50

In creating a surface-rendered image, what can happen if the threshold is set too narrow?
A) actual protruding structures can be imperceptible
B) non-tissue materials, such as fluids, can be displayed as if they were tissue and can obscure protruding structures
C) too much data are included so that less powerful computers may not be able to generate a display
D) the SR image generated cannot be rotated

A) actual protruding structures can be imperceptible

51

Another name for surface rendering is:
A) volume rendering
B) segmentation
C) projection display
D) shaded-surface display

D) shaded-surface display

52

What is the function of the DAC?
A) converts the data into shades of grey that can be displayed
B) converts the digital signal from the computer into an analog signal for the display monitor

B) converts the digital signal from the computer into an analog signal for the display monitor

53

Which is an example of a computer input device?
A) microprocessor
B) primary memory
C) CT detector mechanisms
D) laser camera

C) CT detector mechanisms

54

Which is another name for raw data?
A) image data
B) scan data
C) reconstructed data
D) displayed data

B) scan data

55

The central processing unit (CPU) performs what function?
A) dissipated excessive heat that builds up on the target material
B) interprets computer program instructions and sequences tasks
C) samples detectors

B) interprets computer program instructions and sequences tasks

56

If the main tissue of interest is liver, which of the following is the best approximate WL setting?
A) - 600
B) 0
C) 50
D) 600

C) 50

57

In CT image creation using a third-generation design, a complete set of ray sums is known as?
A) convolution equation
B) algorithm
C) view

C) view

58

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

D) reduced heat capacity

59

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 DFOV
D) two values for a 256 matrix, and 4 values for a 512 matrix

B) one

60

All of the following are scan parameters except:
A) mAs
B) slice thickness
C) matrix
D) pitch

C) matrix

61

A graphical representation of the CT systems capability of passing information through it to the observer is called?

MTF (modulation transfer function)

62

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

A) heat capacity

63

Which of the following is a characteristic of xenon gas detectors?
A) low efficiency
B) sensitive to temperature and moisture
C) may exhibit after glow
D) also called scintillators

A) low efficiency

64

The goal of helical interpolation methods is to:
A) calculate the appropriate mAs for a given patient size
B) take the slant and blur out of the helical image so that they closely resemble images taken from axial methods
C) automatically assign the optimal WW and WL to each reconstructed image
D) eliminate artifacts from voluntary and involuntary patient motion

B) take the slant and blur out of the helical image so that they closely resemble images taken from axial methods

65

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?

Misregistration

66

A precise set of steps to be performed in a specific order to solve a problem describes:
A) an algorithm
B) beam attenuation
C) interpolation
D) back projection

A) an algorithm

67

A magnification factor of 1.5 is used to enlarge the image data, resulting in:
A) a decrease in pixel size
B) an increase in pixel size
C) an inaccuracy in any subsequent distance measurement
D) an image that is larger and may allow more accurate cursor placements for measurements

D) an image that is larger and may allow more accurate cursor placements for measurements

68

The WW of a specific CT image is set at 300, and the WL us 100. How is a structure displayed with a measurement of 280 HU displayed?
A) dark shade of grey
B) light shade of grey
C) white
D) black

C) white

69

Beam attenuation can be defined as

The phenomenon by which an x-ray beam passing through a structure is decreased in intensity or amount because of absorption and interaction with matter

70

Assume the raw data is still available, in what scenario would it be impossible to create an MPR?

Sourse images vary in gantry tilt

71

What does noise mean

You dont have enough data