Photon Interactions Flashcards

1
Q

Name the types of photon interactions:

A
  1. Photo Electric (PE)
  2. Compton Scattering (CS)
  3. Pair Production (PP)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the energy range for each type of photon reaction?

A
  1. PE = 50KeV
  2. CS = 25KeV to 25MeV
  3. PP = >25MeV
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How is each type of photon reaction related to Z?

A
  1. PE = Z^3
  2. CS = independent
  3. PP = Z^2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How is each type of photon reaction related to E?

A
  1. PE = 1/E^3
  2. CS = as E increases, CS decreases
  3. PP = roughly independent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What photon reaction(s) contributes most at 25KeV?

A

PE (50%) and CS (50%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What photon reaction(s) contributes most at 25MeV?

A

CS (50%) and PP (50%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What photon reaction is advantageous for imaging?

A

photoelectric effect (PE)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the target in PE?

A

bound electron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

In PE, as photon energy increases, electron distribution ____?

A

is more forward

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are secondary emissions of PE?

A

auger e’, characteristic x-ray, and electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

PE takes place in what shells?

A

any: K, L, M, N

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What must happen for PE to take place?

A

Photon energy must exceed binding energy of electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What photon reaction is not advantageous to imaging?

A

Compton Scattering (CS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the target in CS?

A

unbound electron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the energy distribution is CS?

A

Low inbound E photon: most energy goes to photon

High inbound E photon: most energy goes to e’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

In CS, a direct hit of an inbound E photon results the electron going in ___ degrees, and the photon in ___ degrees?

A

0 degrees; 180 degrees

17
Q

A CS photon at 90 degrees has an energy of ___?

18
Q

A CS photon at 180 degrees has an energy of ___?

19
Q

What is the E threshold for PP to occur?

20
Q

At what E is PP predominant?

A

E > 25 MeV

21
Q

How is PP related to Z?

A

proportional to Z^2

22
Q

What is the target in PP?

A

the nucleus

23
Q

Pair Production results is what?

A

2 electrons, e- and e+, that share energy (1/4: 3/4)

*similar to beta- and beta+, but NO decay takes place

24
Q

What photon reaction results produces annihilation radiation?

25
How is annihilation radiation produced, and what are the resulting energies?
when an e+ recombines with an e- as a result of PP. 2 511 KeV photons are emitted at 180 degrees apart
26
Define HVL
Width of material to reduce the intensity to half its original value
27
Attenuation characteristics of monoenergetic photons, and what is the formula for the attenuation coefficient?
NO beam hardening: HVL 1 = HVL 2 = HVL 3; u = ln2/HVL = .693/HVL u = attenuation coefficient
28
Define TVL
Avg amount of material needed to absorb 90% of all radiation to reduce the intensity to a tenth of its original value
29
Equation to determine TVL
TVL = 3.32 x HVL
30
Attenuation characteristics of polyenergetic photons
Beam hardening: HVL 1 < HVL 2 < HVL 3, etc... *barriers must get thicker to reduce intensity by 1/2 due to beam hardening; u (poly) < u (mono)
31
PE will always be less than what energy?
< 100 keV
32
At what energy does PE = CS
25 keV
33
At what energy does CS = PP
25 MeV