Chapter 8 Flashcards
X-ray production originate from
electron cloud
Incoming electrons from the cathode =
incident electrons
Travel from thermionic cloud around filament to target of anode at distance of
~2cm
Range from nearly _ speed of
½ speed of light to the speed of light
3 Target Interactions
Bremsstrahlung interactions
• Characteristic interactions
___
Electron Interaction with Target Atoms produce
X-RAYS by 2 processes
Bremsstrahlung interactions
• Characteristic interactions
German word for “braking or slowing”; also referred to as
Brems
What interactions occur when an incident electron passes through orbital shells and approaches the nucleus of the Tungsten atom.
Brems
What gets close to the nucleus because of the power of attraction.
Incident electron
Electron cannot penetrate but the force field causes it to brake (slow down) this change in energy is emitted as an
x-ray photon.
Bremsstrahlung Interaction- list 4 things about it
• Incident electron
• Passes by nucleus
• Changes direction
• Energy released as a photon
Within diagnostic range, most photons are produced by
Brems target interactions.
Photon energy dependent on
how close electron comes to nucleus and the rate of deceleration.
Between 80-100 kVp, about 80-90% of the primary beam is produced by
Brems
Most of the useful beam is of
Brems origin.
What occur when an incident electron interacts with an inner-shell electron, the incident electron will continue but in another direction.
Characteristic Interactions
An electron from another shell will immediately drop into the
vacant hole.
This dropping of an electron from an outer higher energy into an inner low energy state results in the emission of an
x-ray photon.
When outer-shell electrons fill inner-shell vacancies what occurs
a characteristic cascade occurs
This produces several x-ray photons at different energies from each atom.
Characteristic Interactions
Only incident electrons which drop into the __ will produce characteristic photons within diagnostic x-ray range. (characteristic peak)
K-shell
Photons from other shells (L,M,N, etc.) have energies that are too low to be significant in diagnostic radiology. (this is what __ is for)
filtration
kVp must be above __ for characteristic photons to contribute to a diagnostic image, this is due to the binding energy of Tungsten.
70
Between 80-100 kVp, about 10-20% of the primary x-ray beam is produced by.
characteristic interactions
Which spectrum has Continuous emissions wide variety of energy levels.
Brems
What filters low x-ray energies out of the beam (area to far left of curve)
Filtration eliminates
What spectrum discrete emissions of specific energy levels.
Characteristic Spectrum
Factors that affect the emission
spectrum.
mA
kVp
Filter
For mA the larger the area under the curve, the
higher the x-ray quantity
For kVp The farther the right, the
higher the quality (energy) of the x-ray beam and the greater amplitude.
Adding filtration results in reduced quantity but
increased quality of the beam. (decreases amount of low energy x-rays)
Target Material
Higher Z#, increased what and shifts how
amplitude and shift to the right of the curve.
More efficient generators create
higher amplitude
Being human-made is the primary difference between
X-rays and gamma rays
What is the products of nuclear radioactive decay
Gamma rays
What is the distance that electrons that form the thermionic cloud around the filament arrive at the anode target travel
2 cm
The electrons were accelerated from zero to
Half the speed of light in about 2 cm
Incoming electrons are called
Incident electrons
The ones that travel at the speed of light
When incident electrons strike the target, they transfer their tremendous kinetic energy to the atoms of the target material and this interactions produces
Cray photons
The greater the mass or speed of the incident electrons, the greater
The quality (energy) and quantity (number) of photons produced
All target interactions occur within
.25-.5 mm of the surface of the target
A these are two types of target interactions that can produce diagnostic range X-ray photons
Bremsstrahlung and characteristic
