8/26: Production of X-rays II Flashcards
- The flow of electrons through an electrical conductor
a. Electricity
- The amount of electrons flowing through a conductor per second
a. Current
- What are the units for current?
a. Amperes (A)
- The path of an electrical current
a. Circuit
- The difference in electrical potential energy between two points in an electric circuit. Measure in volts (V)
a. Voltage (potential difference)
- What is the half cycle of electricity?
a. 1/120 of a second
- Describe what happens during each half cycle?
a. 1st: anode = + and attracts electrons from cathode to produce x-radiation
b. 2nd: anode = - and no radiation because no electron attraction
- How many electrical cycles do we get in the USA?
a. 60 cycles per second
- What is a full wave rectification?
a. Allows the current to have constant exposure to produce x-rays. Anode is always attracting electrons
- What is rectification?
a. Changing alternating current to direct
- Describe how electricity flows and produces X-rays in terms of full wave rectification?
a. Changes AC into DC
b. Full wave rectification to get high frequency power supply
c. Essentially constant potential between cathode and anode now
d. Higher energy beam compared to AC
- Why can’t we just use DC straight from the wall instead of changing it from AC → DC?
a. DC doesn’t work with transformers
b. Must be AC to DC for it to work
- What is constant potential and direct current important?
a. Shorter exposure times
b. More consistent beam intensity
c. Higher energy beam
d. Decreased radiation dose
- What are the 2 mechanisms for x-ray formation?
a. Bremsstrahlung radiation
b. Characteristic radiation
- What kind of interaction is bremsstrahlung radiation?
a. Electron to nucleus
- What kind of interaction is characteristic radiation?
a. Electrons interact with the tungsten plate (focal spot). This has enough energy to ionize the tungsten
- How is bremsstrahlung radiation created?
a. Electrons slow or stop at the nucleus and energy is transferred as X-ray radiation
- How is characteristic radiation created?
a. Electrons displace inner shell electrons and make radiation
- In bremsstrahlung radiation, do all electrons attain the same velocity?
No
KE =
a. 1/2MV^2
- The higher the velocity, the greater the ____ of electrons
KE
- Bremsstrahlung radiation increases with what?
a. Voltage (kV)
b. atomic number of the target (Z#)
- Bremsstrahlung radiation has what distribution of wavelengths?
a. Wide distribution (heterogenous)
- In what radiation do you have a head-on collision with the nucleus?
a. bremsstrahlung
- In characteristic radiation, atoms become
a. Ionized and unstable
- How is radiation emitted in characteristic radiation?
a. Electron gets displaced and another from outer shell has to fill in and this causes radiation
- What is true about Characteristic radiation?
a. Outer shell electron moves to inner shell
- In characteristic radiation, the energy emitted is equivalent to what?
a. Difference in the binding energies of the 2 shells/orbits
- What percentage of diagnostic x-ray beam is characteristic radiation?
30%
- What percentage of diagnostic x-ray beam is bremsstrahlung radiation?
70%
- Most photons emit what kind of radiation?
a. Bremsstrahlung
