Chapter 4 - 2

Question 1

35. With CR, a higher sampling pitch results in __________ pixel size and __________ spatial resolution.

a. increased; increased
b. increased; decreased
c. decreased; increased
d. decreased; decreased

Answer 1

b. increased; decreased

With CR, a higher sampling pitch results in increased pixel size and decreased spatial resolution.
REF: p.77

Question 2

36. With CR, a higher sampling frequency results in __________ pixel size and __________ spatial resolution.

a. increased; increased
b. increased; decreased
c. decreased; increased
d. decreased; decreased

Answer 2

c. decreased; increased

With CR, a higher sampling frequency results in decreased pixel size and increased spatial resolution.
REF: p.77

Question 3

37. How often the analog signal is digitized is the:

a. sampling frequency.
b. sampling pitch.
c. pixel frequency.
d. pixel pitch.

Answer 3

a. sampling frequency.

Sampling frequency describes how frequently the analog signal will be sampled and digitized.
REF: p.77

Question 4

38. The distance between the analog points being sampled is the:

a. sampling frequency.
b. sampling pitch.
c. pixel frequency.
d. pixel pitch.

Answer 4

b. sampling pitch.

Sampling pitch is the distance between samples of the analog signal. The greater the pitch, the less frequently the sampling takes place.
REF: p.77

Question 5

39. With a fixed matrix CR reader system, changing to a larger IP, for the same FOV, will result in:

a. larger pixels.
b. smaller pixels.
c. improved spatial resolution.
d. B and C.

Answer 5

a. larger pixels.

For the same field of view, spreading the fixed matrix out over a larger IP will result in the pixels being larger and therefore decreased spatial resolution.
REF: p.79

Question 6

40. Pixel bit depth is determined by the:

a. ADC.
b. FOV.
c. matrix.
d. tissue type.

Answer 6

a. ADC.

The analog to digital converter (ADC) determines the pixel depth.
REF: p.79

Question 7

41. Immediately before leaving the CR reader unit, the IP is exposed to:

a. the laser light.
b. developer chemicals.
c. intense white light.
d. x-rays.

Answer 7

c. intense white light.

Just before leaving the CR reader unit, the IP is erased using intense white light exposure.
REF: p.81

Question 8

42. __________ can be removed from the Bucky and is used on the tabletop or a stretcher.

a. Full panel digitizer
b. Flat-panel detector
c. Folding pixel detector
d. Failure to properly digitize

Answer 8

b. Flat-panel detector

The detector system is usually dedicated to a single room and is permanently mounted in the table or upright Bucky system, but flat-panel digital detectors are also available as mobile IRs.
REF: p.81

Question 9

43. The DR detector array is typically located:

a. inside the cassette.
b. by the computer keyboard.
c. on top of the table.
d. where you would normally find the Bucky tray.

Answer 9

d. where you would normally find the Bucky tray.

The DR detector array takes the place of the Bucky tray, because there are no more cassettes needed with this system.
REF: p.82

Question 10

44. DR imaging systems briefly store the electrical charge in the:

a. ADC.
b. TFT.
c. CRT.
d. DQE.

Answer 10

b. TFT.

The electrical charge is briefly stored in the TFT, or thin-film transistor array.
REF: p.82

Question 11

45. The __________ array is divided into square detector elements (DEL).

a. ADC
b. IP
c. TFT
d. SNR

Answer 11

c. TFT

The thin-film transistor (TFT) array is divided into square detector elements (DEL).
REF: p.81

Question 12

46. The percentage of x-rays that have reached the detector and have been captured is the:

a. TFT array.
b. fill factor.
c. ADC.
d. quantization.

Answer 12

b. fill factor.

The percentage of x-ray capture (~80%) is known as the fill factor.
REF: p.82

Question 13

47. Which of the following is not a component of a flat-panel detector?

a. TFT array
b. X-ray converter
c. Glass substrate
d. Phosphor layer

Answer 13

d. Phosphor layer

The flat-panel detector does not include a phosphor layer, although individual detectors may include a phosphor material.
REF: p.81

Question 14

48. The indirect conversion detector uses:

a. a scintillator.
b. a photodetector.
c. amorphous selenium.
d. A and B.

Answer 14

d. A and B.

A detector that is the indirect conversion type uses a scintillator (to convert x-rays to light) and a photodetector. Amorphous selenium is found in the direct conversion type detector.
REF: p.82

Question 15

49. An example of a scintillator used in an indirect conversion detector is:

a. cesium iodide.
b. gadolinium oxysulfide.
c. amorphous selenium.
d. A and B.
e. A and C.

Answer 15

d. A and B.

Scintillators used in the indirect conversion detector include cesium iodide or gadolinium oxysulfide. Amorphous selenium is found in the direct conversion type detector.
REF: p.82

Question 16

50. Which of the following is true about the indirect conversion DR systems?

a. X-rays are converted to light then converted to electrical charges.
b. X-rays are converted to electrical charges.
c. X-rays are converted to electrical charges then converted to light.

Answer 16

a. X-rays are converted to light then converted to electrical charges.

In the indirect conversion DR systems, x-rays are converted to light by a scintillator, and then the light is converted to electrical charges by photodetectors.
REF: p.82

Question 17

51. Which of the following is the sequence of events, from beginning to end, for production of a DR image using direct conversion detectors?
    1 - Image matrix is formed in computer.
    2 - Charge is briefly stored in TFT array.
    3 - Exit radiation is converted to electrical charge.
    4 - Electronic signal goes to ADC.

a. 3, 4, 1, 2
b. 2, 4, 3, 1
c. 2, 3, 4, 1
d. 3, 2, 4, 1

Answer 17

d. 3, 2, 4, 1

With DR imaging, exit radiation is converted to an electrical charge which is briefly stored in the TFT array. The electronic signal then goes to the ADC to be digitized, and the digital information is used to form the image matrix.
REF: p.83

Question 18

52. The ability of the detector to accurately capture the variety of photon intensities in the remnant radiation is:

a. pixel depth.
b. dynamic range.
c. ALARA.
d. pixel sensitivity.

Answer 18

b. dynamic range.

Dynamic range describes how well the detector can capture small to large photon intensities.
REF: p.83

Question 19

53. Compared with film-screen detectors:

a. digital IRs have a much narrower dynamic range.
b. digital IRs have a much wider dynamic range.
c. digital IRs have no dynamic range.

Answer 19

b. digital IRs have a much wider dynamic range.

Compared with film-screen detectors, digital image receptors have a much wider dynamic range.
REF: p.84

Question 20

54. The measurement of the efficiency of an image receptor in converting the x-ray exposure it receives to a quality radiographic image is the:

a. quantum noise.
b. modulation transfer function.
c. detective quantum efficiency.
d. photostimulable luminescence.

Answer 20

c. detective quantum efficiency.

DQE is the measurement of the efficiency of an image receptor in converting the x-ray exposure it receives to a quality radiographic image.
REF: p.85

Question 21

55. The higher the DQE of a system, the radiation exposure required to produce a quality image is:

a. increased.
b. decreased.
c. not effected.

Answer 21

b. decreased.

The higher the DQE of a system, the lower the radiation exposure required to produce a quality image.
REF: p.85

Question 22

56. Overexposing a digital image receptor may result in a quality image, but:

a. quantum noise will be visible.
b. the SNR will be poor.
c. the ALARA principle has not been followed.
d. the system will not last as long as expected.

Answer 22

c. the ALARA principle has not been followed.

Overexposing the image receptor means that the patient was overexposed, going against the ALARA principle.
REF: p.84

Question 23

57. A method of describing the strength of the radiation exposure compared with the amount of noise apparent in the digital image is the:

a. signal-to-noise ratio.
b. contrast-to-noise ratio.
c. modulation transfer function.
d. detective quantum efficiency.

Answer 23

a. signal-to-noise ratio.

Signal-to-noise ratio (SNR) is a method of describing the strength of the radiation exposure compared with the amount of noise apparent in the digital image.
REF: p.85

Question 24

58. A high SNR means that the:

a. signal strength is high.
b. signal strength is low.
c. noise is high.
d. B and C.

Answer 24

a. signal strength is high.

High signal-to-noise ratio (SNR) means that the signal strength is high, and the noise is low.
REF: p.86

Question 25

59. __________ the SNR increases the visibility of anatomic details. a. Increasing b. Decreasing c. Maintaining

Answer 25

a. Increasing Increasing the SNR increases the visibility of anatomic details, whereas decreasing the SNR decreases the visibility. REF: p.86

Question 26

60. A method of describing the contrast resolution compared with the amount of noise apparent in a digital image is the: a. signal-to-noise ratio. b. contrast-to-noise ratio. c. modulation transfer function. d. detective quantum efficiency.

Answer 26

b. contrast-to-noise ratio. Contrast-to-noise ratio is a method of describing the contrast resolution compared with the amount of noise apparent in a digital image. REF: p.86

Question 27

61. __________ the CNR increases the visibility of anatomic details. a. Increasing b. Decreasing c. Maintaining

Answer 27

a. Increasing Increasing the CNR increases the visibility of anatomic details, whereas decreasing the CNR decreases the visibility. REF: p.86

Question 28

62. Which of the following is not accomplished through the histogram analysis? a. Compensation for image underexposure b. Identification of the edges of the image c. Manipulation of image contrast d. Compensation for image overexposure

Answer 28

c. Manipulation of image contrast Histogram analysis primarily compensates for overexposure and underexposure. REF: p.87

Question 29

63. The histogram analysis represents the __________ for different exposure levels. a. intensity of exposure b. incidence of pixels c. exposure index d. all of the above

Answer 29

b. incidence of pixels The histogram analysis represents the incidence (or number) of pixels for different exposure levels. REF: p.87

Question 30

64. The range of the histogram data set that should be included in the displayed image is determined by the: a. LUT. b. EI. c. VOIs. d. LCD.

Answer 30

c. VOIs. The values of interest (VOIs) determine which values from the histogram analysis will be used in the image. REF: p.88

Question 31

65. In CR imaging, the __________ of the imaging plate is scanned. a. exposed portion b. top half c. bottom half d. entire area

Answer 31

d. entire area The entire CR imaging plate is scanned during readout. REF: p.88

Question 32

66. All of the data from the entire IP (including scatter outside the exposed field) may be included in the histogram analysis if: a. only one edge of the collimated field is identified. b. only three edges of the collimated field are identified. c. all four edges of the collimated field are identified. d. all of the above.

Answer 32

a. only one edge of the collimated field is identified. If three or four field edges are identified, the computer will accurately eliminate the data from outside the exposed area of the IP. If only one edge of the field is identified, the computer includes all data in the histogram analysis. REF: p.88

Question 33

67. Based on the histogram analysis, consistent image brightness is accomplished through: a. adjustment of window width b. automatic rescaling c. manipulation of the exposure indicator d. manipulation of the LUT

Answer 33

b. automatic rescaling Automatic rescaling adjusts the data in the histogram analysis to produce consistent image brightness. REF: p.88

Question 34

68. The numerical value indicating the level of radiation exposure to the digital IR is the: a. VOI b. histogram c. exposure indicator d. LUT

Answer 34

c. exposure indicator The exposure indicator describes the amount of exposure to the digital IR. REF: p.88