Electron and Photon Interactions

Electron interactions produce ________

Photons

Where do electron interactions occur

At the target

Where is the target located

Anode

What are photon interactions

How x-rays interact with matter

What are the 2 electron interactions

1. Bremsstrahlung

2. Characteristic

What general energies do Bremsstrahlung Interactions occur in

MV and KV

Where do Bremsstrahlung Interactions occur

Near nucleus

What happens during Bremsstrahlung Interactions

• electron slows down and changes direction

• Energy is released as a Bremsstrahlung x-ray

For Bremsstrahlung: the closer the e- gets to the nucleus, the _______ (lower/higher) x-ray energy

Higher

Which electron interaction is the only one that occurs in MV ranges

Bremsstrahlung

Electrons in characteristic interactions interact with _________ ________

Orbitig electrons

What happens during electron interactions

• an incoming e- ejects an outer shell e-

• An orbiting electron moves in to fill the gap from the ex-electron

• Energy is released as characteristic x-ray as the gap is filled

What are the outer shells?

• K

• L

• M

Which shell is the furthest from the nucleus

M

Which shell has the highest binding energy

K

Which electron interaction is most useful in diagnostic ranges

Characteristic

T/F: Characteristic interactions are useful in therapy

False

What are the 5 types of photon interactions

1. Coherent

2. Compton

3. Photodisintegration

4. Pair production

5. Photoelectric

Which photon interactions interact with an outer shell electron?

• Coherent

• Compton

For Coherent and Compton, when the photon interacts with the outer shell e-, does it change direction?

Yes

With ________ (coherent/Compton) scatter, no energy is lost or absorbed

Coherent

With _______ (coherent/Compton) scatter, some energy is released

Compton

What is the most common interaction in XRT

Compton

Which photon interaction only excites e-, but doesn't lose any energy

Coherent

Coherent scatter occurs in ____ (low/high) energies

Low

Coherent scatter occurs in energies <____ kev

10

Which photon interaction reduces image quality in Dx images

Compton

Which photon interactions occur in the nucleus

• Pair production

• Photodisintegration

Which photon interaction releases a neutron

Photodisintegration

Which photon interaction does magic and reappears as an e- pair

Pair Production

What happens in Pair production

• Photon interacts with nucleus, disappears, and reappears as an electron pair

What is the energy of an electron

0.512 MeV

What is the energy threshold in Pair Production?

>1.022 MeV

• 0.511 + 0.511

Which photon interaction occurs with High Z materials

Photodisintegration

Photodisintegration occurs in energies >__ MeV

10

Z stands for

Atomic #

Atomic number is the amount of _______ in the nucleus

Protons

Which photon interaction involves an inner shell electron

Photoelectric

Which photon interaction involves the Photon energy being completely absorbed by an electron

Photoelectric

Tip: Photoelectric interactions

• Photon interacts with Inner shell e-, which has higher binding energy

• So capable absorbing all of photon energy

• That electron is then ejected because it has TOO MUCH energy

• Becomes a photoelectron

Yeah

What is a secondary interaction of photoelectric effect

Characteristic interaction

• another outer shell e- fills in the gap and releases energy

What is the most common photon interaction in Diagnostic Ranges?

Photoelectric

Photoelectric effect __________ (inc/Dec) with increasing photon energy

Decreases