Chapter 2 - 2

Question 1

33. The advantage to having a focal track is that:

a. the focal spot will be smaller.
b. the focal spot will be larger.
c. lower exposure factors can be used.
d. higher exposure factors can be used.

Answer 1

Solution: d. higher exposure factors can be used

When the stream of electrons constantly has a new area of the target to hit, the result is that higher exposure factors can be used.
REF: p.18

Question 2

34. __________ envelopes are more commonly used in today’s x-ray tubes.

a. Glass
b. Paper
c. Metal
d. Lead

Answer 2

Solution: c. Metal

Metal envelopes are more commonly found in today’s x-ray tube, replacing glass envelopes.
REF: p.19

Question 3

35. As compared to glass, which of the following is an advantage to having a metal envelope x-ray tube?

a. Decrease in off-focus radiation
b. Increase in off-focus radiation
c. Increased deposits of tungsten on the inside surface of the envelope
d. A and C

Answer 3

Solution: a. Decrease in off-focus radiation

The metal x-ray tube envelope results in less off-focus radiation being produced.
REF: p.20

Question 4

36. Inside the x-ray tube envelope you will find:

a. oil
b. air
c. A and B
d. none of the above

Answer 4

Solution: d. none of the above

The x-ray tube envelope has been evacuated, leaving a vacuum present.
REF: p.20

Question 5

37. The speed the electrons inside the x-ray tube travel is:

a. the speed of light.
b. approximately one half the speed of light.
c. dependent on the mAs set.
d. dependent on the exposure time set.

Answer 5

Solution: b. approximately one half the speed of light

The electrons in the tube current travel at approximately one half the speed of light.
REF: p.20

Question 6

38. Diagnostic x-ray exposures range from:

a. 15 to 40 kVp.
b. 20 to 65 kVp.
c. 30 to 150 kVp.
d. 60 to 225 kVp.

Answer 6

Solution: c. 30 to 150 kVp

The kVp in the diagnostic x-ray range varies from approximately 30 to 150.
REF: p.20

Question 7

39. With a standard x-ray tube, ____________% of the x-ray beam produced with 65 kVp is the result of bremsstrahlung interactions.

a. 0
b. 15
c. 85
d. 100

Answer 7

Solution: d. 100

With a standard x-ray tube, 100% of the x-ray beam produced with 65 kVp is the result of bremsstrahlung interactions. The electrons must have at least 69.5 keV to produce characteristic radiation.
REF: p.20

Question 8

40. With a standard x-ray tube, ____________% of the x-ray beam produced with 90 kVp is the result of bremsstrahlung interactions.

a. 0
b. 15
c. 85
d. 100

Answer 8

Solution: c. 85

With a standard x-ray tube, 85% of the x-ray beam produced with 90 kVp is the result of bremsstrahlung interactions.
REF: p.20

Question 9

41. With a standard x-ray tube, ____________% of the x-ray beam produced with 65 kVp is the result of characteristic interactions.

a. 0
b. 15
c. 85
d. 100

Answer 9

Solution: a. 0

With a standard x-ray tube, 0% of the x-ray beam produced with 65 kVp is the result of characteristic interactions. The electrons must have at least 69.5 keV to produce characteristic radiation.
REF: p.21

Question 10

42. With a standard x-ray tube, ____________% of the x-ray beam produced with 90 kVp is the result of characteristic interactions.

a. 0
b. 15
c. 85
d. 100

Answer 10

Solution: b. 15

With a standard x-ray tube, 15% of the x-ray beam produced with 90 kVp is the result of characteristic interactions.
REF: p.21

Question 11

43. X-ray photon energy is measured in:

a. kVp
b. mA
c. angstroms
d. keV

Solution: d. keV

Answer 11

X-ray photon energy is measured in keV.
REF: p.22

Question 12

44. The wide range of energies in the x-ray beam is known as the:

a. monoenergetic spectrum.
b. x-ray emission spectrum.
c. gamma ray emission spectrum.
d. x-ray transmission spectrum.

Answer 12

Solution: b. x-ray emission spectrum

The x-ray beam is polyenergetic (has many energies) and consists of a wide range of energies known as the x-ray emission spectrum.
REF: p.22

Question 13

45. The highest energy x-ray photons produced with a 100 kVp exposure will be:

a. 50 keV.
b. 75 keV.
c. 100 keV.
d. 125 keV.

Answer 13

Solution: c. 100 keV

In that the p in kVp stands for peak, the highest energy produced with a 100 kVp exposure is 100 keV.
REF: p.22

Question 14

46. When making an exposure, which of the following does not occur when just the rotor, or prep button, is activated?

a. The anode begins to rotate.
b. Voltage is applied across the tube.
c. Current is applied to the filament.
d. A space charge is created.

Answer 14

Solution: b. Voltage is applied across the tube

Voltage is not applied across the tube until the exposure button has been pressed.
REF: p.24

Question 15

47. Filament current is approximately:

a. 0.5 to 2 mA
b. 3 to 5 mA
c. 0.5 to 2 A
d. 3 to 5 A

Answer 15

Solution: d. 3 to 5 A

It takes about 3 to 5 A of current passing through the filament to produce enough thermionic emission to create a space charge.
REF: p.23

Question 16

48. During x-ray production, the energy of the moving electrons is converted into:

a. kinetic energy.
b. thermal energy.
c. electromagnetic energy.
d. A and C.
e. B and C.

Answer 16

Solution: e. B and C

The kinetic energy of the electrons is converted into thermal (heat) and electromagnetic (x-ray) energies.
REF: p.16

Question 17

49. The quality of the x-ray beam indicates:

a. the number of photons.
b. the ability of the photons to penetrate.
c. the quantity of radiation.
d. whether or not the photons were made well.

Answer 17

Solution: b. the ability of the photons to penetrate

X-ray beam quality refers to the penetrability of the photons.
REF: p.26

Question 18

50. Doubling mA results in:

a. doubling the tube current.
b. doubling the quantity of x-ray photons.
c. doubling the thermionic emission.
d. all of the above.

Answer 18

Solution: d. all of the above

Doubling the mA results in twice the thermionic emission, twice the tube current, and twice the number of x-ray photons produced.
REF: p.30

Question 19

51. Decreasing the exposure time results in:

a. fewer x-ray photons.
b. more x-ray photons.
c. higher photon energy.
d. lower photon energy.

Answer 19

Solution: a. fewer x-ray photons

Fewer x-ray photons are produced when the exposure time is shortened.
REF: p.30

Question 20

52. How much is the mAs when 400 mA and 100 ms are used?

a. 4 mAs
b. 40 mAs
c. 400 mAs
d. 4000 mAs

Answer 20

Solution: b. 40 mAs

Since mAs is mA × exposure time, 400 mA × 0.100 s is equal to 40 mAs.
REF: p.30

Question 21

53. When electrons strike the anode target, their kinetic energy is converted into _____% heat and _____% x-rays:

a. 1; 99
b. 99; 1
c. 0; 100
d. 100; 0
e. 50; 50

Answer 21

Solution: b. 99; 1

Most of the electron kinetic energy in the tube current (>99%) is converted into heat, whereas less than 1% of it is converted into x-rays.
REF: p.24

Question 22

54. The larger the anode angle, the:

a. larger the actual focal spot.
b. smaller the actual focal spot.
c. larger the effective focal spot.
d. smaller the effective focal spot.

Answer 22

Solution: c. larger the effective focal spot

Based on the line focus principle, the larger the anode angle, the larger the effective focal spot.
REF: p.33

Question 23

55. Due to the anode heel effect, the difference in intensities between the ends of the x-ray field can be as much as:

a. 10%
b. 25%
c. 45%
d. 60%

Answer 23

Solution: c. 45%

The intensities between the anode and cathode ends of the x-ray field can vary as much as 45% due to the anode heel effect.
REF: p.34

Question 24

56. Added tube filtration is typically made of:

a. lead
b. tungsten
c. glass
d. aluminum

Answer 24

Solution: d. aluminum

Added tube filtration is usually made of aluminum.
REF: p.35

Question 25

57. X-ray tubes operating above 70 kVp must have total filtration of at least __________ of aluminum, or its equivalent. a. 0.5 mm b. 1 mm c. 2 mm d. 2.5 mm

Answer 25

Solution: d. 2.5 mm X-ray tubes operating above 70 kVp must have total filtration of at least 2.5 mm of aluminum, or its equivalent. REF: p.35

Question 26

58. As kVp increases, beam penetrability __________. a. increases b. decreases c. stays the same

Answer 26

Solution: a. increases As kVp increases, beam penetrability increases. REF: p.27

Question 27

59. The amount of heat produced from any given exposure is called a: a. heat unit. b. three-phase generator. c. focal track. d. Hounsfield unit.

Answer 27

Solution: a. heat unit A heat unit is the amount of heat produced by any given x-ray exposure. REF: p.37

Question 28

60. How many HU are produced when using a three-phase x-ray unit, 400 mA, 200 ms, and 70 kVp? a. 5600 HU b. 7560 HU c. 5,600,000 HU d. 7,560,000 HU

Answer 28

Solution: b. 7560 HU Heat units for a three-phase unit are equal to the kVp × mA × exposure time × 1.35, which in this case equals 400 × 0.2 × 70 × 1.35, or 7560 HU. REF: p.37

Question 29

61. Setting identical exposure factors, *which* type of x-ray unit will produce the greatest heat? a. Single phase b. Double phase c. Three phase d. High frequency

Answer 29

Solution: d. High frequency A high-frequency x-ray generator will produce the greatest heat. REF: p.37

Question 30

62. In order to produce 12 mAs, how long should the exposure time be when using 600 mA? a. 0.002 s b. 0.02 s c. 0.2 s d. 2 s

Answer 30

Solution: b. 0.02 s Since mAs is equal to mA × exposure time, exposure time is equal to the mAs divided by the mA. In this example that would be 12 mAs divided by 600 mA or 0.02 s. REF: p.31

Question 31

63. *Which* of the following practices will extend the life of the x-ray tube? 1. Use low mA and longer exposure time. 2. Warm up the tube as appropriate. 3. Hold down the rotor button for a long time, to keep the tube warmed up.

Answer 31

a. 1 and 2 only b. 1 and 3 only c. 2 and 3 only d. 1, 2, and 3 Solution: a. 1 and 2 only In order to have the tube last longer, it is recommended that lower mA, longer exposure time, and tube warm-up as appropriate be practiced. The rotor button should be depressed for as little time as possible. REF: p.39

Question 32

1 T/F When an electron from the L-shell of the tungsten atom is ejected from its orbit by a projectile electron, high-energy x-ray photons are produced.

Answer 32

False Very low-energy X-rays are produced when an L-shell electron is ejected from its orbit. REF: p.21

Question 33

2 T/F The x-ray beam produced with 120 kVp will consist primarily of X-rays produced by bremsstrahlung interactions.

Answer 33

True Approximately 85% of the x-ray beam produced at 120 kVp will consist of X-rays produced by bremsstrahlung interactions. REF: p.20