X-ray Interactions at Target Anode
What is the primary function of the x-ray tube?
To accelerate electrons from the cathode to the anode within the tube
What is the required minimum kVp we need to produce a characteristic x-ray?
69 kVp
What does Bremsstrahlung mean?
Braking Radiation in German
Explain the difference between a discrete emission spectrum and a continuous emission spectrum and which x-ray interaction fits in each graph.
Discrete emission spectrum graphs only contain specific values. Characteristic x-rays are graphed using discrete emission spectrums.
Continuous emission spectrums contain all possible values. Bremsstrahlung x-rays are graphed using continuous emission spectrums.
Why does only the amplitude move with an increase in mAs on continuous emission spectrums?
Because an increase in mAs increases the beam quantity, which means more electrons are being boiled off the filament to be used in x-ray production.
How is electron kinetic enegy increased?
By increasing kVp
Which target anode material is required to efficiently produce x-rays?
Tungsten
In the diagnostic range, most x-rays being produced are....
Bremsstrahlung x-rays
Why are characteristic x-rays graphed using discrete emission spectrums?
Because they have precisely fixed energies.
Explain why kVp affects both the amplitude's height and positioning on a continuous emission spectrum?
An increase in kVp means an increase in beam quantity and quality which is reflected with a taller amplitude as well as a physical shift to the right on the graph.
How is heat produced within the x-ray tube?
By projectile electrons interacting with the target anode outer shell electrons and raising them to an excited state. When these outer shell electrons drop back to their normal energy level, heat is emitted as a byproduct.
How is a characteristic x-ray created?
The projectile electron interacts with an inner shell target anode electron (K shell electron) which knocks it out of its shell. Another outer shell electron will then cascade down and take the originals place, with the binding energy being released forming an x-ray.
How is a brems x-ray created?
The projectile electron interacts with the nuclear field of the atom. While it passes through the target anode atom, it avoids interacting with the target electrons, slowly down as it approaches the nucleus, then changes direction. A photon is produced after the projectile electron slows down, its energy being the difference between the starting energy the projectile had before it ended the target atom and the energy it had after leaving the target atom.
Why are bremsstrahlung x-rays graphed using a continuous emission spectrum?
Because brems x-rays have a range of energy values the photons can have.
What does adding filtration do to the x-ray beam?
Reduces quantity by removing low energy photons while increasing quality as there is an increase in the average energy overall.
What percentage of interactions that occur within the tube actually produce x-rays?
1%
If a K-shell electron is ejected and is replaced by a N-shell electron, what is the energy the Characteristic x-ray photon will have?
1 keV = N-shell binding energy
69 - 1 = 68 keV
What is the range of energies a brems x-ray photon could have if the x-ray tube utilizes a kVp of 80?
0-80 keV
What are the factors that affect discrete emission spectrums?
Tube current, by making the graph taller or shorter
Target material, changes the keV needed to produce a characteristic x-ray photon
What happens when the atomic number of the target material increases?
The efficiency of x-ray production increases, which leads to an increase of high energy photons as well as an increase of the number of photons being produced.
True or False: Heat production is increased proportionately with increasing x-ray tube current.
True
Explain binding energy in terms of Characteristic X-rays.
Binding energy is the energy holding the atom all together. We utilize binding energies of the electron shells in figuring out the energy a characteristic x-ray will have.
At 100 kVp, ___% of the x-ray beam will be characteristic, while ___% will be brems.
15%; 75%
What are the factors that affect continuous emission spectrums?
Tube current, amplitude either rises or lowers
Tube voltage, amplitude rises or lowers and shifts to the right or left
Added filtration, amplitude will lower with a shift to the right
Target material, changes the actual shape of the emission spectrum
Voltage waveform, also changes the actual shape of the emission spectrum
Which generator is the most efficient type of generator to use for x-ray production?
High frequency generators.