RAD 255 - Test 4 - Production of X-Rays

Source of electrons, Accelerate the electrons (Potential energy to force electrons from cathode to anode), Decelerate the electrons (Interaction with high atomic number atom)

What conditions must be present in the x-ray tube for the production of X-rays to occur?

Bremsstrahlung and Characteristic

What are the 2 types of x-ray production?

- Projectile electron approaches nucleus

- Positive charge of nucleus attracts e-

- Electron is veered from it's path & slowed

- Causes a change in direction of the e-

- Electron loses kinetic energy

- Energy lost is emitted as Brems radiation

What happens at the atomic level in Bremsstrahlung Radiation?

- Projectile e- interacts with K-shell electron

- Electron is knocked out its shell

- Empty space is left in k-shell (making the atom unstable)

- L-shell moves down into vacant space

- L-shell electron releases potential energy as it moves down to fill vacancy

- Energy released is characteristic radiation

What happens at the atomic level in Characteristic Radiation?

Brems is characterized by a continuous range of energies (wavelengths).

Characteristic is characterized by discrete or specific energies as dictated by the binding energies of the involved electrons.

Why is Brems radiation "continuous" or heterogeneous as compared to characteristic which consists of "discrete" energy levels?

85-90%

What percentage of Brems radiation is produced?

10-15%

What percentage of Characteristic radiation is produced?

can be produced at any kVp level

What is the kVp requirement for Bremsstrahlung radiation?

at least 70 (to overcome the binding energy)

What is the kVp requirement for Characteristic radiation?

- the further away the electron is from the nucleus, the less the electron slows down which results in less intensity x-ray photons.

- the closer the electron is to the nucleus, the more the electron slows down which results in a higher intensity x-ray photons to be produced.

What factors govern the strength or energy of Brems radiation?

L to K

For characteristic radiation, know which electron shell transition produces x-rays with enough energy to be used diagnostically? (L to K, M to L, N to M etc.)

Upon returning to a stable state, the electron emits infrared radiation (heat) as the electron returns to its original shell.

What is the difference between heat production and x-ray production?

99%

What is the percentage of heat production?

1%

What is the percentage of x-ray production?

if either is doubled the heat production is also doubled

How does heat production in the x-ray tube vary with changes in mA and KVp?

Bremsstrahlung - continuous

Characteristic - discrete

What are the energy levels of both types of radiation in terms of "discrete" vs. continuous?

has a high melting point so it does not melt when high speed electrons slam into it

What happens in the tungsten atom to cause heat?

L to K

What characteristic x-ray electrons involved with the production of useful diagnostic radiation: L to K transition vs. M to L transition or N to M electron transition?

Bremsstrahlung - heterogeneous

Characteristic - homogeneous

What is a one-word description (in terms of energy levels) of the photons that make up the entire x-ray beam if Brems and Characteristic radiation is mixed. (homogeneous vs. heterogeneous)?

69.53 keV

What is the binding energy for the K-Shell?

12.10 keV

What is the binding energy for the L-Shell?

2.82 keV

What is the binding energy for the M-Shell?

0.60 keV

What is the binding energy for the N-Shell?

69.5 - 12.1 = 57.4 KeV

What is the formula to calculate the energy of a K-characteristic x-ray photon from the L-shell? (L to K)

69.5 - 2.8 = 66.7 KeV

What is the formula to calculate the energy of a K-characteristic x-ray photon from the M-shell? (M to K)

69.5 - 0.6 = 68.9 KeV

What is the formula to calculate the energy of a K-characteristic x-ray photon from the N-shell? (N to K)