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Bushong Radiology Physics > Ch. 7 X-ray production > Flashcards

Ch. 7 X-ray production Flashcards

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1
Q

Kinetic energy is…

A

energy in motion

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2
Q

Objects in motion have kinetic energy proportional to their…

A

mass and to the square of their velocity

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3
Q

KE =

A

1/2 mv^2 (m= mass; v = velocity)

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4
Q

all electrons have the same…

A

mass

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5
Q

In an xray tube the projectile is the…

A

electron

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6
Q

electron kinetic energy is increased how?

A

by raising the kVp

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7
Q

When electron kinetic energy is increased what happens/

A

both the intensity (quantity) and energy (quality) of the xray beam are increased

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8
Q

What is the distance of the filament to the xray tube target?

A

about 1 cm

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9
Q

How fast are the electrons moving from the time it leaves the filament to the time it hits the target?

A

almost half the speed of light

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10
Q

What are projectile electrons?

A

electrons traveling from cathode to anode

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11
Q

What happens when projectile electrons hit the heavy metal atoms of the xray tube target?

A

They transfer their kinetic energy to the target atoms

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12
Q

What do the projectile electrons interact with?

A

orbital electrons or the nuclear field of target atoms.

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13
Q

What is the result of the interactions between the projectile electrons and orbital electrons?

A

a conversion of electron kinetic energy into thermal energy (heat) and electromagnetic energy in the form of infrared radiation and xrays.

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14
Q

How much of the projectile electron kinetic energy is used for the production of xrays?

A

only 1%

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15
Q

doubling the xray tube current doubles what?

A

it doubles the heat produced

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16
Q

Heat production increases directly with…

A

increasing kVp

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17
Q

The efficiency of xray production increases with…

A

increasing kVp

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18
Q

When are characteristic xrays produced?

A

When a projectile electron interacts with an inner shell electron of the target atom rather than with an outer shell electron.

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19
Q

When the interaction is sufficiently violent to ionize the target atom through total removal of an inner shell electron what happens?

A

characteristic xrays

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20
Q

Characteristic xrays are emitted when an ____ electron fills and _____ void.

A

outer shell; inner shell

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21
Q

The transition of an orbital electron from an outer shell to an inner shell is accompanied by…

A

the emission of an xray

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22
Q

The energy of an xray is equal to…

A

the difference in the binding energies of the orbital electrons involved.

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23
Q

The energy from M-K, N-K, O-K, and P-K can be…

A

calculated

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24
Q

When are characteristic x-rays produced?

A

when the target atom is ionized by removal of electrons from shells other than the K shell.

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25
Q

Only the K-characteristic x-rays of ____ are useful for imaging.

A

tungsten

26
Q

Characteristic x-rays can only be produced at specific…

A

energies equal to the differences in electron-binding energies for the various electron transitions.

27
Q

Why is characteristic x-ray production called characteristic?

A

Because it is characteristic of the target element.

28
Q

The effective energy of characteristic x-rays increases with…

A

increasing atomic number of the target element.

29
Q

The production of hea and characteristic x-rays involves interactions between…

A

the projectile and the electrons of x-ray tube target atoms.

30
Q

Describe a bremsstrahlung interaction.

A

Bremsstrahlung x-rays are produced when a projectile electron is slowed by the nuclear field of a target atom nucleus.

31
Q

What does the word bremsstrahlung mean?

A

it is a german word meaning slowed down radiation

32
Q

Bremsstrahlung x-rays can be considered radiation that results from…

A

the braking of projectile electrons by the nucleus.

33
Q

A projectile electron can lose any amount of its kinetic energy in an interaction with the nucleus of a target atom and the bremsstrahlung x-ray associated with the loss can take on what?

A

the corresponding values

34
Q

How does a low energy brems x-ray result?

A

When the projectile electron is barely influenced by the nucleus.

35
Q

How does a high energy brems x-ray result?

A

when the projectile electron loses all its kinetic energy and simply drifts away from the nucleus.

36
Q

What kind of brems x-rays are most frequent?

A

The ones between low and highest energy.

37
Q

In diagnostic range, which type of x-rays are the most common?

A

brems

38
Q

What does the energy of the electron have to be in order to create at brems x-ray?

A

it can be at any energy

39
Q

A discrete spectrum contains….and a continuous spectrum contains….

A

only specific values….all possible values

40
Q

What kind of x-ray spectrum do characteristic x-rays have?

A

the energies of characteristic x-rays are fixed so the emission spectrum would be discrete

41
Q

The Brem x-ray emission spectrum extends from ___ to ____

A

0 to maximum projectile electron energy

42
Q

The highest number of brem x-rays only have about ____ of the maximum energy of the beam.

A

1/3

43
Q

Brem x-rays have a ___ of energies and form a _____ emission spectrum.

A

range; continuous

44
Q

With brems, the number of x-rays emitted ____ at very low energies.

A

decreases

45
Q

The energy of an x-ray is equal to..

A

the product of its frequency and Planck’s constant

46
Q

x-ray energy is inversely proportional to what?

A

its wavelength

47
Q

As x-ray wavelength increases, x-ray energy….

A

decreases

48
Q

If the curve of an emission spectrum goes to the right what does that indicate?

A

he higher the effective energy or QUALITY of the x-ray beam

49
Q

The larger the area under the curve of an emission spectrum indicates…

A

higher x-ray intensity or QUANTITY

50
Q

A change in mA or mAs results in what kind of change in the emission spectrum?

A

a change in the amplitude but not the position

51
Q

As kVp is raised, how does the emission spectrum change? (factor)

A

the area under the curve increases to an area approximating the square of the factor by which kVp was increased.

52
Q

When kVp changes, how does the appearance of the spectrum change?

A

in amplitude and position

53
Q

What is the % of change in kVp that needs to happen to be equal to doubling mAs?

A

15%….15/50 rule

54
Q

What affect does adding filtration have on the beam?

A

It reduces intensity while increasing the average energy.

55
Q

What is a word used when adding filtration to a beam?

A

hardening

56
Q

Does the atomic number of the target affect the quantity and quality of the beam? How?

A

yes as the atomic number of the target material increases, the efficiency of the production of bremsstrahlung radiation increases, and high energy x-rays increases in number to a greater extent than low energy x-rays.

57
Q

What are the 5 voltage waveforms?

A

half wave rectified, full wave rectified, 3 phase/6 pulse, 3 phase/12 pulse, and high frequency

58
Q

What is the relationship between full wave and half wave rectified?

A

They are the same except for the frequency of x-ray pulse repetition.

59
Q

What is the relationship between 3 phase/6 pulse and 3 phase/12 pulse?

A

There is reduced ripple with 12 pulse generation compared with 6 pulse generation

60
Q

What produce the lowest voltage ripple of all high voltage generators?

A

high-frequency generators

61
Q

Because of reduced ripple, operation with 3 phase power or high frequency is equivalent to ….

A

about 12% increase in kVp, or almost a doubling of mAs over single phase power.

Bushong Radiology Physics (12 decks)

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