Electron Target Interactions

X ray and heat production:

-electrons travel from cathode to anode(1-3 cm) at half the speed of light

-Called projectile electrons

-Some negative electrons are not sufficient energy to ionize target atoms

99% of Kinetic energy of projectile e- is converted to heat

As KV goes up so does efficiency

60 Kv=.5%, 100kV=1%, 20/MV=70%

Projectile electrons

Electrons traveling from cathode to anode that constitute the x-ray tube current.

Bremsstrahlung Radiation

-"Braking radiation." The sudden deceleration of electrons as they interact with highly positively charged nuclei.

-Occurs when the negative electrons decelerate near the nucleus of Tungsten atom


-Does NOT involve - in the orbital tungsten shells

-Constitutes 90% of emitted radiation

-As Z goes up Brems atomic number and strength goes up

-Average X-ray energy is 1/3 of the original

the higher the atomic number, the more ______ _________

Brems radiation

Characteristic radiation

A form of radiation that occurs when a high speed electron dislodges an inner shell electron from an atom, causing excitation, or ionization of the atom

What are facts some facts about Characteristic radiation?

-Negative electron interacts with inner shell negative electron and ejects it

-Negative Electron from outer shell fills hole and produces X-ray photon

-K Shell negative e is the only one with sufficient energy for radiography!!!!!

-The energy of these photons is characteristic of target material(difference in binding energies

k shell xray

-K-shell emission produces higher-intensity x-rays than Bremsstrahlung, and the x-ray photon comes out at a single wavelength.

-When outer-shell electrons drop into inner shells, they emit a quantized photon "characteristic" of the element.

What happens to the number and strength of characteristic radiation photons when you increase mA

The number of characteristic radiation protons increases proportionally; the strength(energy) stays the same

What happens to the number and strength of brems radiation when you increase mA

Both the Number of Photons AND strength(energy) of photons increase proportionally

What happens to the number and strength of brems radiation when you increase kV?

KV boosts the quality AND quantity of Brems radiation; in other words both go up

What happens to the number and strength of characteristic radiation photons if you increase kV?

Energy/Strength would remain constant; number of photons would increase

If you make the filtration on an x ray tube stronger what else would increase?

The quality of the X-rays that penetrate the patient increases resulting in more effective Brens radiation,

What decreases with stronger filtration on the x ray tube?

The number of brems and characteristic radiation decreases; and decreases low energy X rays penetrating patient

What happens to the strength and number of brem and characteristic radiation when Z increases

Both the strength and the number of these rays get bigger when the atomic number gets higher.