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Dosimetry Physics 1 > Exam Review 9/4 PPT4 > Flashcards

Exam Review 9/4 PPT4 Flashcards

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1
Q

the process of an atom acquiring a positive
or negative charge

A

ionization

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2
Q

___ ionization - occurs when a particle (charged) such as an electron, proton or alpha particle collides with matter to produce a charged particle.

A

direct

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3
Q

___ ionization - occurs when an uncharged particle or radiation such as a photon or neutron liberate a directly ionizing particle when they interact with matter.

A

indirectly

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4
Q

the number of photons that pass through an
imaginary cross section of a sphere

A

fluence

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5
Q

the fluence per unit time

A

Fluence rate or flux density

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6
Q

Compton is dominant in the diagnostic or therapy energy range?

A

Therapy

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7
Q

Photelectric is dominant in the diagnostic or therapy energy range?

A

Diagnostic

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8
Q

What interaction occurs at Low photon Energy and High Z?

A

Coherent scatter (aka classical/Rayleigh)

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9
Q

Coherent scatter only occurs at energies ___

A

less than 10 KeV

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10
Q

the probability of what interaction increases by Z^3 and decreases by E^3?

A

Photoeltric Effect

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11
Q

What interaction is this? The photon interacts with an atom and ejects on of the orbital electrons. The photon gives 100% of its energy to the ejected electron.

A

Photelectric

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12
Q

in the ___ (type of interaction), a domino effect may then occur with the discrete energies being emitted and even giving off Auger electrons

A

photoelectric effect

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13
Q

in the photelectric effect, a domino effect may then occur with ___ being emitted and even giving off ___

A

discrete energies (characteristic x-ray), Auger electrons

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14
Q

Which of the following interactions could result in an Auger e-, scattered photon, ejected e-, etc

A

…

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15
Q

Which of the following interactions could result in an Auger e-, scattered photon, ejected e-, etc

A

..

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16
Q

Which of the following interactions could result in an Auger e-, scattered photon, ejected e-, etc

A

..

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17
Q

Compton occurs at what energies?

A

25KeV to 10MeV

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18
Q

What interaction is this? An incoming photon hits an outer orbital electron & not all energy is transferred. This results in an ejected electron and a weaker photon.

A

Compton

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19
Q

In the ___ the binding energy of the e- must be __ than the energy of the __

A

compton effect, e-, photon

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20
Q

interaction that is independent of Z

A

compton

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21
Q

Compton side scatter (right angle - 90 degrees) energy:

A

.511 MeV

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22
Q

Compton backscatter (180 degrees) energy:

A

.255MeV

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23
Q

Compton: If you increase E, angular dependence is ___, so photon scatter is also more ___

A

more forward-peaked, forward

24
Q

What does this image show?

A

If you increase E, angular dependence is more forward-peaked, so photon scatter is also more forward

25
Q

What does this graph show?

A

As energy increases, bone and tissue absorption become the same - poor contrast (why MV images are poor quality)

26
Q

What interaction is this?
An incoming photon interacts with the nucleus and gives up all of its
energy in creating a positron and negatron

A

Pair production

27
Q

Pair production probability increases with __.

A

Z^2

28
Q

Pair production energy threshold:

A

1.02 MeV

29
Q

Positron loses energy and combines with a free electron to give rise to two annihilation photons with .511MeV each.

A

Annihilation reaction

30
Q

When ____ (type of interaction) occurs, it can recombine to form an annihilation reaction.

A

pair production

31
Q

Reaction that occurs when a nucleus absorbs a high-energy photon and a particle is ejected from the nucleus

A

Photodisintegration

32
Q

Photodisintegration energy threshold

A

> 10 MeV

33
Q

y, n reaction occurs at what energy?

A

> 10 MV

34
Q

y, n reaction occurs where ?

A

gantry head

35
Q

y, n reaction causes?

A

unwanted neutron production (contamination)

36
Q

y, n reaction is more common in what materials?

A

high Z

37
Q

Elastic or inelastic collision?
Total kinetic energy of all particles is the same before and after collision

A

elastic

38
Q

Elastic or inelastic collision?
some kinetic energy is lost and becomes excited or ionized

A

inelastic

39
Q

Describe what is happening in the graph

A

For a small energy range, water is a better attenuator than lead
Compton is independent of Z

40
Q

“Dose deposited increases very slowly at first, then very sharply near the end
of the range before dropping to almost zero value” describes?

A

Bragg Peak

41
Q

kinetic energy loss per unit path-length

A

stopping power

42
Q

stopping power formula

A

MeV/cm or 2Mev/cm

43
Q

Biologic effects of radiation result primarily in damage to ___

A

DNA

44
Q

atoms of the target become ionized or excited and lead t events resulting in biologic change

A

direct action

45
Q

radiation interacts with other atoms to produce free radicals that then do the damage to critical target

A

indirect action (usually water)

46
Q

measure of the rate at which energy is transferred from ionizing radiation to soft tissue

A

LET (linear energy transfer)

47
Q
A

Coherent scatter

48
Q
A

photoelectric

49
Q
A

photoelectric

50
Q
A

Coherent Scatter

51
Q
A

Compton

52
Q
A

Compton

53
Q
A

Compton

54
Q
A

Pair production

55
Q
A

Pair production to annihilation reaction:
Positron loses energy and combines with a free electron to give rise to two annihilation photons with .511M

56
Q
A

photodisintegration

57
Q

Fluence rate or flux density

A

fluence per unit time

Dosimetry Physics 1 (7 decks)

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