Exam Review 9/4 PPT4

Question 1

the process of an atom acquiring a positive
or negative charge

Answer 1

ionization

Question 2

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

Answer 2

direct

Question 3

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

Answer 3

indirectly

Question 4

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

Answer 4

fluence

Question 5

the fluence per unit time

Answer 5

Fluence rate or flux density

Question 6

Compton is dominant in the diagnostic or therapy energy range?

Answer 6

Therapy

Question 7

Photelectric is dominant in the diagnostic or therapy energy range?

Answer 7

Diagnostic

Question 8

What interaction occurs at Low photon Energy and High Z?

Answer 8

Coherent scatter (aka classical/Rayleigh)

Question 9

Coherent scatter only occurs at energies ___

Answer 9

less than 10 KeV

Question 10

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

Answer 10

Photoeltric Effect

Question 11

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.

Answer 11

Photelectric

Question 12

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

Answer 12

photoelectric effect

Question 13

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

Answer 13

discrete energies (characteristic x-ray), Auger electrons

Question 14

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

Answer 14

…

Question 15

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

Answer 15

..

Question 16

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

Answer 16

..

Question 17

Compton occurs at what energies?

Answer 17

25KeV to 10MeV

Question 18

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.

Answer 18

Compton

Question 19

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

Answer 19

compton effect, e-, photon

Question 20

interaction that is independent of Z

Answer 20

compton

Question 21

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

Answer 21

.511 MeV

Question 22

Compton backscatter (180 degrees) energy:

Answer 22

.255MeV

Question 23

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

Answer 23

more forward-peaked, forward

Question 24

What does this image show?

Answer 24

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

Question 25

What does this graph show?

Answer 25

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

Question 26

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

Answer 26

Pair production

Question 27

Pair production probability increases with __.

Answer 27

Z^2

Question 28

Pair production energy threshold:

Answer 28

1.02 MeV

Question 29

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

Answer 29

Annihilation reaction

Question 30

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

Answer 30

pair production

Question 31

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

Answer 31

Photodisintegration

Question 32

Photodisintegration energy threshold

Answer 32

>10 MeV

Question 33

y, n reaction occurs at what energy?

Answer 33

> 10 MV

Question 34

y, n reaction occurs where ?

Answer 34

gantry head

Question 35

y, n reaction causes?

Answer 35

unwanted neutron production (contamination)

Question 36

y, n reaction is more common in what materials?

Answer 36

high Z

Question 37

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

Answer 37

elastic

Question 38

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

Answer 38

inelastic

Question 39

Describe what is happening in the graph

Answer 39

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

Question 40

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

Answer 40

Bragg Peak

Question 41

kinetic energy loss per unit path-length

Answer 41

stopping power

Question 42

stopping power formula

Answer 42

MeV/cm or 2Mev/cm

Question 43

Biologic effects of radiation result primarily in damage to ___

Answer 43

DNA

Question 44

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

Answer 44

direct action

Question 45

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

Answer 45

indirect action (usually water)

Question 46

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

Answer 46

LET (linear energy transfer)

Question 47

Answer 47

Coherent scatter

Question 48

Answer 48

photoelectric

Question 49

Answer 49

photoelectric

Question 50

Answer 50

Coherent Scatter

Question 51

Answer 51

Compton

Question 52

Answer 52

Compton

Question 53

Answer 53

Compton

Question 54

Answer 54

Pair production

Question 55

Answer 55

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

Question 56

Answer 56

photodisintegration

Question 57

Fluence rate or flux density

Answer 57

fluence per unit time