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73 Cards in this Set
- Front
- Back
What is the function of an x-ray generator
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-A n x-ray generator provides power to the x-ray tube.
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What do x-ray generators control
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x-ray energy
exposure duration total exposure |
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What are the 3 main components of an x-ray generator
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high voltage transformer
filament transformer rectifier circuits |
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Where are the electronic circuits for voltage and current meter located
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this is part of the x-ray generator
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Does the generator have electronic circuits for manual and automatic exposure
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yes
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What type of voltage is used in the US
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120V alternatic current (AC)
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What is the frequency of ossilation of a AC in the united states
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60hz
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What is the voltage required for x-ray tube generators
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440V
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What 2 things must be accomplished by the X-generator
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A generator increases the voltage and rectifies the waveform from AC to direct
current (DC). It must be increased to 440V |
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What type of current is required for a x-ray generator to work
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Direct current
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What 3 controls are operated when using an X-ray generator
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X-ray tube voltage (Kilovolts)
current (mA) exposure time |
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What does the x-ray voltage control
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the x-ray energy
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What does the current afffect
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the radiation quanity
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Where is the voltage applied
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across the x-ray tube and current flows through the x-ray tube
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What is the power used by the X-ray generator
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Th e power dissipated equals the product of tube voltage (V) in kilovolts and of current in milliamperes (I), or V x I, and is measured in kilowatts (kW).
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What is the typical transformer rating
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Typical transformer ratings in x-ray departments are 100 kV and 800 mA, which
correspond to a power of 80 kW. |
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How high can the voltage that a generator produces become
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100,000V
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What is the function of a transformer
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A transformer changes the size of the input voltage and is used to produce high and
low voltages. |
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What is the function of a step-up transformer
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increase the voltage
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What is the function of a step-down transformer
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decrease the voltage
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Give an example of electromagnetic induction
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I f two wire coils are wrapped around a common iron core, current in the primary
coil produces a current in the secondary coil by electromagnetic induction. |
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What is the voltage in a circuit proportional to
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I f two wire coils are wrapped around a common iron core, current in the primary
coil produces a current in the secondary coil by electromagnetic induction. |
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What law of physics is taken advantage of to manipulate the current
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Th e product of the voltage (V) and current (I) is equal to the power and must be
equal in the two circuits (conservation of energy) if there are no additional losses. -Fo r an ideal transformer, the power in the primary and secondary circuits will be equal, so that Vp x Ip = Vs x Is. |
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What is the principle behind step up and step down transformers
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Th e step-up transformers used in x-ray generators have a secondary coil with many
more turns (500:1) to produce a high voltage across the tube. -Generators also have a step-down transformer with fewer turns in the secondary coil for the x-ray tube filament circuit, which only requires about 10 V. |
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What is an autotransformer
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A n autotransformer permits adjustment of the output voltage, using movable con-tacts to change the number of windings in the circuit.
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What is a transformer
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electromagnetic devices that allow a voltage of AC to be changed
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Can a transformer decrease or increase the voltage
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yes
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What are the 2 types of transformers used in an x-ray generator
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step up
step down |
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What are transformers comprised of
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two sets of windings that are electrically isolated from eachother
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What is the function of each of these windings
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One set of windings is connected to a power supply and is known as the primaries. The other set of windings is connected to a load (in this case the X-ray tube) and is referred to as the secondary windings.
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What does a transformer look like
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Why is this done
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How does the electric current flow in with AC power
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Th e electric current from an AC power supply flows alternately in both directions,
resulting in a voltage waveform shaped like a sine wave. |
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What is rectification
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Rectification changes the AC voltage into DC voltage across the x-ray tube.
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How is rectification achieved
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Rectification is achieved using diodes, which only permit current to flow in one di-rection.
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What do diodes do
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only permit current to flow in one direction
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Does rectification ensure that electrons travel from cathode to anode only
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yes
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Do transformers require AC current to work
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yes
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So what must be done after the voltage is created by the transformer
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it must be made so it is constant and not rising and falling
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What does rectified voltage look like
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What is half wave rectification
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one direction of current is eliminated
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What does half wave rectification look like
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What does a full wave rectifier look like
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What does a single phase generator wave form look like
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What does the 3, 6 and 12 pulse 3 phase generator waves look like
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Are high frequency generators smaller and more efficient than three phase generators
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yes
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What are the best generators
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high frequency generators
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What is a voltage waveform
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a plot of voltage over time
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What is ripple
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A constant high voltage is desired across the x-ray tube for x-ray production, but in
practice, there is some variation in the voltage, which is called ripple. |
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What type of ripple is preferred
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A low ripple is desirable because a more constant voltage is produced.
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What is the voltage for the different types of phase generators
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these are all voltage waveforms
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What keV is required to produce diagnostic x-ray
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Diagnostic x-rays are produced when electrons with energies of 20 to 150 kilo
electron volts (keV) are stopped in matter, producing electromagnetic radiation in the form of x-rays. |
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What determines the keV of an electron
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the applied voltage
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What is the kinetic energy of electrons converted into
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heat and x-rays when the electron strikes the anode
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What happens to the electron as it strikes the anode
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Electrons only penetrate tens of micrometers (μm) into the anode before losing
their energy by ionization and excitation of electrons in the anode material. |
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What interaction occurs after the electron hits the t
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Energetic electrons loose their energy in matter by excitation, in which electrons are
energized to higher energy states; ionization, in which an outer-shell electron is re-moved; and radiation, in which the energy loss is converted directly to a photon. |
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Electron hitting the anode
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What happens to the electron after it is released by the cathode
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After the electrons are emitted from the cathode, they come under the influence of an electrical force pulling them toward the anode. This force accelerates them, causing an increase in velocity and kinetic energy.
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What happens to the kinetic energy as the electron travels from the cathode to the anode
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This increase in kinetic energy continues as the electrons travel from the cathode to the anode.
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What happens the the potential energy as the electron travels from the cathode to the anode
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As the electron moves from cathode to anode, however, its electrical potential energy decreases as it is converted into kinetic energy all along the way.
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What is the ratio of kinetic to potential energy as the electon reaches the anode
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Just as the electron arrives at the surface of the anode its potential energy is lost, and all its energy is kinetic
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What determines the energy of the electron as it hits the anode
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its velocity
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What happens to the electron as it hits the anode
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When the electrons strike the surface of the anode, they are slowed very quickly and lose their kinetic energy; the kinetic energy is converted into either x-radiation or heat
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What type of radiation is produced as the electron hits the anode
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Two types of interactions produce radiation. An interaction with electron shells produces characteristic x-ray photons; interactions with the atomic nucleus produce Bremsstrahlung x-ray photons.
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What interactions occur as the electron hits the anode
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Do the energetic electrons interact with the electrons of the atom (on the anode)
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yes, An interaction with electron shells produces characteristic x-ray photons
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Does characteristic X-ray production result in ionization of the target atom
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yes
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What causes the anode to heat
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Energy lost in the form of excitation and ionization appears as heat in the anode.
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What are the 2 types of radiation produced
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Bremsstrahlung radiation
Characteristic radiation |
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What is an example of efficiency of an X-ray
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Th e efficiency of x-ray production is approximately kV x Z x 10 − 6 and is ap-proximately 1% for materials with high atomic numbers (Z) at 100 kVp.
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What is a graph of x-ray tube output showing the number of photons at each x-ray energy
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spectrum
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