LRA-222 Week 1 X-ray Circuit Flashcards
define current
- flow of electrons in an electrical circuit
define direct current
- electrons flowing in one direction
- used in the x-ray tube
- also known as DC
define alternating current
- moving rapidly back and forth
- used in transformers
- also known as AC
define batteries
- simple power source that provide direct current
- one side is positive, and the other is negatived
- when a battery is electrically charged, electrons flow from the negative side to the positive side
define voltage
- difference in charge
- creates the current
explain DC in the graph
- the voltage is stable over time
- no fluctuation
- one direction only
what are the common sources of AC electricity?
- coal
- nuclear
- wind
- alternating current is created inly by specialized generators
explain AC in the graph
- the voltage is unstable
- goes up and down
- fluctuates
does the x-ray circuit/system use AC or DC?
AC
does the x-ray tube use AC or DC?
DC
true or false: x-ray tubes function only with AC
true
true or false: commercial produced current in the US is AC
true
define rectification
- process of converting AC to DC
- also known as diode
- electrical current only goes one way (such as DC)
- when a rectifier is added to the circuits, the electrons flowing in the reverse/opposite direction are blocked
define half wave rectification
- half of the wave is blocked
- there is still a remaining gap between the waves
define full wave rectification
- the waves in the reverse directions are converted /switched to all flow in the same direction
true or false: step-up and step-down transformers work in the AC
true
define transformers
- change the voltage in an electrical circuit
what are the types of transformers?
- step up
- step down
- autotransformer
define step-up transformer
- increases voltage
- decreases amperage
define step-down transformer
- decreases voltage
- increases amperage
why do x-rays need a step-up transformer?
- they need a high voltage to create x-ray photons
why does the filament circuit need a step-down transformer?
- a high amperage is needed
name the transformer components
- core
- primary coil
- secondary coil
define primary coil
- where electricity comes in
define secondary coil
- where electricity comes out
how does voltage change?
- through electromagnetic induction
define autotransformer
- can increase and decrease the voltage or amperage
- can act as both a step-up and a step-down
- makes small changes to the voltage
- adjustable
define mutual conduction
- 2 coils
- primary coil
- secondary coil
whats the difference between the autotransformer and the step up/step down transformer?
- the autotransformer only has 1 coil acting as both the primary and secondary coils
define phase
- number of wave cycles in a circuit
- number of distinct waves
- single and three phase
define frequency
- number of pulses
define pulses
- number of voltage pulses per cycle
define single phase
- most basic
- one distinct waveform
define voltage ripple
- change in voltage with each pulse
- goes from 100% to 0% (disadvantage)
- not many photons will heat the patient
- low beam energy, low intensity, less photons, and fewer penetrations
define three phase (alternating current)
- three different waveforms creating the current through the circuit
- 3 currents
define three phase - six pulse
- voltage ripple is reduced to 14%
- because there are several waves, there is no gap which decreases the voltage ripple
- 6 currents
define three phase - twelve pulse
- voltage is smaller, standing at 4%
- 12 currents
define high frequency
- voltage ripple is 1%
- thousands of pulses per wave cycle
define kilovoltage
- kV or kVp
- x-ray tube potential (penetration)
- controls energy, frequency, and wavelength of each photon
define milliamperage
- mA
- x-ray tube current
- controls number of photons int he x-ray beam
flat waveforms ensure:
- correct x-ray output
- correct x-ray energy
- optimal image quality
- optimal patient dose
true or false: a perfect kV waveform generates the selected kV from the very beginning till the end
true
why does overshoot and undershoot occur?
due to not generating the assigned kV
what are the components to correct waveforms?
- make sure the kV waveform is flat
- adjust the output kV to match the assigned kV
- recheck and adjust the kV waveform as needed
what are the results of an incorrect kV waveform?
- saturation
- mottle
- excess patient dose
- generator faults
define rotor spike
- a current spike that occurs in the mA waveform before normalizing to the assigned mA
- very normal
true or false: after the kV waveform is calibrated, the mA waveform must be calibrated for every mA station available on every kV setting the machine can generate
true
true or false: mA waveform must be regularly updated as the tube ages to ensure optimal performance
true
what are the results of an incorrect mA waveform effect?
- saturation
- mottle
- excess patient dose
- generator faults
define the primary circuit
- main power supply
- primary side of the step-up transformer
what are the 3 components of the x-ray circuit?
- primary circuit
- secondary circuit
- filament circuit
define circuit breaker
- protects the rest of the circuit
- it breaks the circuit and stops the incoming electrical power from moving into the x-ray machine
- making sure there isn’t excessive energy coming in (as it could damage the circuit)
what type of energy is in the primary circuit, Volts or Kilovolts?
- volts (v)
define autotransformer
- changes kVp to different settings
- uses single coils
- self induction
define kVp meter
- volts are easier to measure and reading can be easily turned into kilovolts (kV)
define exposure timer
- control how long the exposure stays on
define step up transformer
- primary side only
- electricity is still in volts
define mutual induction
- the step-up increases volts to kilovolts
name the components in the primary circuit
-circuit breaker
- autotransformer
- kVp meter
- exposure time
- step-up transformer (primary coil)
define the secondary circuit
- secondary side of the step-up transformer
- where x-ray tube is located
- uses direct current only (DC)
define rectifier
- converts alternating current (AC) into direct current (DC)
- causes current to flow in one direction
- where x-ray tube converts electrons into x-ray
name the components in the secondary circuit
- step-up transformer (secondary coil)
- rectifier
- x-ray tube
define the filament circuit
- contains the cathode filaments in the x-ray tube
define rheostat
- controls heat in the filaments
- resistor that’s connected to the mA selector control panel
- when mA changes, the setting on the rheostat is also changed
define step-down transformer
- voltage is decreasing
- amperage is increasing (increases heat, electrons, and x-rays)
what type of current is used in the filament circuit?
- alternating current (AC) is used in order for the step down to function
what is the amperage in the filament current?
- 3-6 amperage (high)
- the amperage must be high in order for thermionic emission to occur
true or false: when the operator sets the tube current (mA), the rheostat adjusts the filament current (amps)
true
what are the 5 general principles of electrostatics?
- Like charges repel and unlike charges attract.
- The electrostatic force between two charges is directly proportional to the product of their quantities and inversely proportional to the square of the distance between them (also known as Coulomb’s law).
- Electric charges reside only on the external surface of conductors.
- The concentration of charges on a curved surface of a conductor is greatest where the curvature is greatest.
- Only negative charges (electrons) are free to move in solid conductors.
define electrostatic
- study of stationary electric charges
define electrodynamic
- study of electric charges in motion
- “electricity”
define coulomb’s law
- The electrostatic force between two charges is directly proportional to the product of their quantities and inversely proportional to the square of the distance between them
what are the 3 ways an object may be electrified?
- friction
- contact
- induction
define electric potential
- the ability to do work because of a separation of charges
- Ex.) Battery
define resistance
- property of an element in a circuit that resists or impedes the flow of electricity
name the 3 expressions of electrical phenomenon
- electric potential
- current
- resistance
define volt
- the expression of the difference in electric potential between two points
define ampere
- the amount of current flowing with an electric potential of 1 volt in a circuit with a resistance of 1 ohm
define conduction band
- electrons from the conductor’s atoms will move out of the valence shell to a higher energy level just beyond
define resistance
- the property of a circuit element that impedes the flow of electricity
name the 4 things a resistance depends on
- material
- length
- cross sectional area
- temperature
define conductors
- materials with an abundance of free electrons that allow a relatively free flow of electricity
what some examples of conductors
- copper
- gold
- water
define insulators
- atoms with tightly bound electrons and do not conduct electricity well even when attracted by a potential difference
what are some examples of insulators?
- rubber
- plastic
- glass
- wood
- ceramic
define semiconductors
- These materials will conduct electricity but not as well as conductors, and they will insulate but not as well as insulators
what are some examples of semiconductors
- silicon
- germanium
- diamond
define electric circuit
- a closed pathway composed of wires and circuit elements through which electricity may flow
what 2 types of circuits are there?
- closed circuit
- open circuit
define closed circuit
- pathway for electricity must be closed/complete for electricity to flow
define open circuit
- when a pathway is broken
what are the 3 elements of a circuit?
- series
- parallel
- combination
define grounding
- Grounding is a process of neutralizing a charged object by placing it in contact with the earth. Positively charged objects take electrons from the earth until neutral, and negatively charged objects give up electrons to the earth until neutral.
define electromagnetic induction
- Current may be induced to flow in a conductor by moving that conductor through a magnetic field or by placing the conductor in a moving magnetic field.
define electric generator
- devices that convert some form of mechanical energy into electrical energy
define electric motors
- devices that convert electrical energy to mechanical energy through electromagnetic induction
define circuit breaker
- protect against short circuits and electric shock.
define automatic exposure control (AEC)
- uses the patient’ s body part of interest as the variables in determining when to terminate exposure
- the length of exposure is determined by the thickness and density of the area of the patient placed over the ionizing chamber
