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Radiation Therapy > Physics chapter 5 powerpoint > Flashcards

Physics chapter 5 powerpoint Flashcards

1
Q

What is binding energy?

A

the amount of energy needed to remove an orbital electron from an atom

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2
Q

What is the name of the force that attracts electrons to the nucleus?

A

Coulomb force

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3
Q

Binding energy is greatest in the shells that are ________ to the nucleus.

A

closest

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4
Q

Binding energy is _______ for larger atomic numbers.

A

higher

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5
Q

Characteristic radiation consists of only _________ x ray energies.

A

discrete

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6
Q

For tungsten _____ keV is the energy difference between K and L shells.

A

59

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7
Q

A change in _______ energy is responsible for x ray emission in bremsstrahlung x ray production.

A

kinetic

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8
Q

The amount of energy involved in a bremsstrahlung interaction depends on:

A

distance from the nucleus

charge of the nucleus

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9
Q

X rays are emitted in all directions in _______ energies.

A

diagnostic

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10
Q

As electron beam energy increases, x rays are emitted more _______.

A

forward

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11
Q

In high energy therapy energies, x rays are emitted mostly in a __________ direction.

A

forward

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12
Q

What does the output beam spectrum do?

A

depict fraction of beam act each energy value through a combination of bremsstrahlung and characteristic x ray representation

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13
Q

the lowest energy photons are filtered and do not escape from the tube due to the ________.

A

glass port

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14
Q

True or false: Bremsstrahlung maximum changes with kVp.

A

True

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15
Q

what is the range of energy for bremsstrahlung?

A

0 to whatever kVp was set on the generator

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16
Q

True or false: energies change on the spectrum from changes in mA.

A

false

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17
Q

What changes in proportion to change in mA?

A

number of photons

18
Q

True or false: characteristic x ray energies do not change from a change in kVp.

A

True

19
Q

What is beam hardening?

A

once lower energy photons are removed, a greater HVL is required than the first

20
Q

Why are filters used?

A

to block low energy photons that would not contribute to the image but would only increase the dose

21
Q

Intensity decreases with ________ and _________.

A

distance

attenuation

22
Q

What are the assumptions of the inverse square law?

A

it is from a point source

there is no attenuation

23
Q

What 3 things can happen to a photon?

A

nothing

scatter

absorption

24
Q

What is narrow beam attenuation?

A

scatter is removed

only absorption considered

25
Q

What is broad beam attenuation?

A

both scatter and unabsorbed radiation is considered

26
Q

what is the attenuation equation for narrow beam mono energetic photons applied to?

A

for photons that are neither absorbed nor scattered

27
Q

the attenuation coefficient ___________ with increasing beam energy.

A

decreases

because high energy beam is more penetrating

28
Q

Poly energetic beams are produced by ________.

A

x ray tubes

29
Q

mono energetic beams are produced by ___________-.

A

radionuclide sources

30
Q

What is the half value layer?

A

the absorber thickness that reduces beam intensity to exactly half

31
Q

What is HVL an indication of?

A

beam quality

32
Q

Higher HVL means:

A

more penetrating beam

lower attenuation coefficient

33
Q

What is the average distance traveled by photon before interacting equation?

A

x (average)= 1/linear attenuation coefficient

34
Q

For ___________ radiation, there are fewer photons after absorption and the average energy does not change.

A

mono energetic

35
Q

for Mono energetic radiation, the 1st HVL is ______ to the 2nd.

A

same

because the average energy does not change

36
Q

In ________ radiation, lower energy photons are attenuated more than higher energy photons.

A

poly energetic radiation

37
Q

In poly energetic radiation, the 1st HVL is ______ the 2nd.

A

less than

38
Q

In polyenergetic radiation, _______ increases and the beam becomes more ________.

A

average energy

penetrating

39
Q

What are the units of mass attenuation coefficient?

A

g/ cm^2

40
Q

What is the mass attenuation coefficient?

A

the linear attenuation coefficient divided by density

or

the distance (x) multiplied by density

41
Q

What variable expresses attenuation of a material independent of its physical state?

A

mass attenuation coefficient

Radiation Therapy (26 decks)

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