Production of X-Rays

X-rays are a type of ___ radiation

electromagnetic

Low frequency electromagnetic waves have a ___ wavelength

long

High frequency electromagnetic waves have a ___ wavelength

short

What is the wavelength range for x-rays?

0.1-0.5 Å

What are the 3 conditions required for x-ray production?

1. source of electrons (heated filament)

2. means of accelerating electrons (high voltage)

3. means of decelerating electrons (target)

Production of x-rays occur when ______ moving electrons are suddenly ______ by interaction with target material

fast, decelerated

Production of x-rays occurs within ___ to ___ mm of target surface

0.25 to 0.5

Energy =

quality

Amount =

quantity

X-ray is directly proportional to the ___ energy of the incident electrons

kinetic

What are the steps for heat production?

1. electrons interact with outer-shell electrons of the target (anode) atoms

2. Outer-shell electrons raised to a higher, or excited, energy level (shakes)

3. energy is insufficient to ionize target atoms

4. electrons immediatly drop back to normal/relaxed state

5. transition accompanied by infrared radiation (heat)

What is another word for incident electrons?

projectile electrons

What are the two types of target interactions that produce x-ray photons?

Bremsstrahlung and characteristic

The type of target interaction depends on ________ and ________

kinetic energy of incoming electron and binding energy of electron shells

electrons give up energy to target atoms

In a Bremsstrahlung interaction, the high speed incident electron __________

passes near the nucleus (has enough energy to pass through the orbital shells)

“Brems” also means ______ or ______ in German

“braking” or “slowing”

Brems interactions make up ____% to _____ % of the primary beam

80% to 90%

In a Bremsstrahlung interaction, the ___ deflects the electron from its original path of travel

positive charge of the nucleus

What is electrostatic force?

power of force field

What type of interaction is this?

What is A in this image?

What is B in this image?

Bremsstrahlung interaction

A: incident electron

B: Bremsstrahlung x-ray photon

Loss of kinetic energy given off as an x-ray photon is ___

Brems radiation

Energy of Brems radiation depends on what 3 things?

1. the energy of the incident electron

2. the charge of the nucleus

3. the proximity of the incident electron to the nucleus

In a Bremsstrahlung interaction, interactions that take place closer to the nucleus have a ___ energy Brems

higher

In a Bremsstrahlung interaction, interactions that take place farther from the nucleus have a ___ energy Brems

lower

In a Bremsstrahlung interaction, the incident electron may lose ___ of its kinetic energy in an interaction with the nucleus

any amount

The average beam energy is ____ to ___ % of kVp selected in Brems Radiation

30% to 40%

When 70 kVp is set on the control panel, explain the Brems radiation

• kinetic energies up to 70 keV are produced

• electrons may lose all, some or none of their kinetic energy

• Brems x-rays produced may have energies up to 70 keV

Brems radiation energies are ________

Very low energy photons are absorbed ___

Unpredictable

within the tube

What is heterogenous/polyenergetic beam?

contains a variety of energies

In this image, if A is 60 kV and B is 10 kV, what is the kV of C?

50 kV

(60 - 10 = 50)

In this image, if B is 25 kV and C is 15 kV, what is the kV of A?

40 kV

(25 + 15 = 40)

Characteristic reactions make up ___% of the primary beam

10-20%

Characteristic x-rays are emitted when ___

an outer shell electron fills an inner shell void

In characteristic interactions, the incoming electron ___

ejects inner shell (K shell) electron

What type of interaction is shown in the image?

characteristic interaction

What is the cascade effect?

In characteristic interactions, each electron shell releases less and less energy as electrons fill in the gaps

Why is the type of radiation interaction predictable?

we know the binding energies of the shells of the target atom (tungsten)

What is the atomic number of Tungsten?

How many protons does it have?

How many neutrons does it have?

How many electrons does it have?

atomic #: 74

P: 74

N: 110

E: 74

How many electrons are in the K shell of Tungsten?

2

What is the approximate binding energy for the K shell of Tungsten?

69.5 keV

X-ray energy equals the difference in ___ of the orbital electrons involved

binding energy

Electrons dropping into the K shell may be from ___

any shell (not always the subsequent one)

The further out the electron comes to “drop” into a vacancy, the ___ the characteristic radiation produced

greater

Only ___ shell characteristic interactions contribute to the useful beam

K

Characteristic radiation interaction will only occur at ___

69.5 keV and above

(if <70 kVp is selected, there will only be Brems interactions)

Define energy (in terms of characteristic radiation interactions)

the difference in binding energy of the shells involved

What are C and D on this graph (the axes)?

C: # of photons

D: energy (keV)

What is A on this graph?

What is B on this graph?

A: maximum energy

B: average energy

What type of interaction does this graph depict?

Brems

What point on this graph is determined by the kVp you set?

A

What type of interaction does this graph depict?

characteristic

What shell is represented by letter A?

What shell is represented by letter B?

A: L shell x-rays

B: K shell x-rays

What are the C and D on this graph (the axes)?

C: # of photons

D: energy (keV)

What are the vertical lines on this graph called?

characteristic peaks

Characteristic x-rays are only emitted at ___

70 kVp and above

Bremsstrahlung x-rays are emitted over ___

entire spectrum of beam

Average beam energy is ___% of set kVp

30-40%

___ determines the # of electrons that boil off during thermionic emission and # of x-ray photons in beam

mAs

___ determines the penetrability of beam

kVp

When the curve of the graph shifts to the right, this means that the energy ___

has increased

Increased generator efficiency leads to a(n) ___ average photon energy and a(n) ___ number of photons in beam

increased; increased