XRAY TUBE AND XRAY PRODUCTION Flashcards by Danie Bernal

What type of enclosure is used in X-ray tubes?

Glass or metal enclosure

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What type of device is an X-ray tube?

A special type of diode (anode and cathode)

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What is the main function of an X-ray tube?

Converts electrical energy into electromagnetic energy

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What are the three main external components of an X-ray tube?

Support structure, protective housing, and glass/metal enclosure

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What is the most frequently used X-ray tube support system?

Ceiling-support system

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What does the preferred detent position mean?

When the X-ray tube is centered above the examination table at the standard SID

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What is the function of protective housing in X-ray tubes?

Insulates against electric shock, dissipates heat, and supports the tube mechanically

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What is isotropic emission in X-ray tubes?

Emission with equal intensity in all directions

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What is leakage radiation?

X-rays that escape through protective housing

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What is the primary material used for the glass enclosure in X-ray tubes?

Pyrex glass

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What are the advantages of metal enclosures in X-ray tubes?

Longer tube life and constant electric potential

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What are the two primary parts of the cathode in an X-ray tube?

Filament and focusing cup

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What material is the filament in an X-ray tube made of?

Thoriated tungsten

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What is the role of the focusing cup in an X-ray tube?

Surrounds the filament and controls electron flow

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What is space charge in the context of X-ray tubes?

A cloud of electrons emitted by the filament

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What is the space charge effect?

Difficulty emitting subsequent electrons due to electrostatic repulsion

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What is the saturation current in an X-ray tube?

The maximum filament current when all electrons are used

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What is the focal spot in an X-ray tube?

The region of the anode target where electrons produce X-rays

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What are the sizes of focal spots typically used?

Small (0.1-1 mm) and large (0.3-2 mm)

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What material is commonly used for the anode in X-ray tubes?

tungsten

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What are the three primary functions of the anode?

Conducts electricity, dissipates heat, and provides mechanical support

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What is the main cause of tube failure in X-ray systems?

Tungsten vaporization and arcing

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A design to allow a large area for heating while maintaining a small focal spot

line focus principle

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What is the anode heel effect?

Greater radiation intensity on the cathode side compared to the anode side

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X-rays produced outside the focal spot

off-focus radiation

What are the three ways heat is dissipated in an X-ray tube?

Radiation, conduction, and convection

What causes damage to the rotor assembly in X-ray tubes?

Excessive heat during long exposure times

What is the unit for heat energy in X-ray applications?

Heat units (HU)

What is the formula for heat units in a single-phase system?

HU = kVp × mA × s

What is the formula for heat units in a high-frequency system?

HU = 1.45 × kVp × mA × s

What is the difference between characteristic and bremsstrahlung X-rays?

Characteristic X-rays are discrete, while bremsstrahlung X-rays have a continuous spectrum

What is the efficiency of X-ray production dependent on?

Tube voltage (kVp)

What happens when target material atomic number increases?

Efficiency and energy of X-rays increase

Reduces low-energy X-rays, increasing the average energy of the beam

added filtration

What does a radiographic rating chart indicate?

Safe and unsafe radiographic techniques

X-rays produced when electrons are slowed by the target nucleus

bremsstrahlung radiation

X-rays produced when an outer electron fills an inner-shell void

characteristic radiation

Electrons traveling from the cathode to the anode

projectile electron

What is the main purpose of a rotating anode?

Provides a larger target area and dissipates heat more effectively

What materials are used in mammographic targets?

Molybdenum (Z=42) and Rhodium (Z=45)

What is the typical rotation speed of a rotating anode?

3,600 to 10,000 rpm

Connects the anode to the rotor while minimizing heat conduction

anode stem

What is the material used for the anode stem?

Molybdenum

What are the two principal parts of an electromagnetic induction motor in an X-ray tube?

Stator and rotor

Where is the stator located in an X-ray tube?

Outside the enclosure

Where is the rotor located in an X-ray tube?

Inside the glass envelope

What is the coast time of the rotor?

Approximately 60 seconds

How does the line focus principle affect the effective focal spot?

Decreases its size compared to the actual focal spot

What happens to the anode heel effect as the target angle decreases?

The heel effect becomes more pronounced

What is the central ray in X-ray imaging?

The imaginary line generated by the centermost X-ray in the beam

What are the consequences of off-focus radiation?

Increases skin dose, reduces image contrast, and exposes unintended tissues

How can off-focus radiation be reduced?

Using a fixed diaphragm or a metal enclosure X-ray tube

What is the most frequent cause of abrupt tube failure?

Electron arcing due to vaporized tungsten

What is the primary cause of filament failure in X-ray tubes?

Tungsten vaporization

What are the three types of rating charts used in X-ray systems?

Radiographic rating chart, anode cooling chart, and housing cooling chart

What does the radiographic rating chart specify?

Safe exposure levels for X-ray tube operation

Determines thermal capacity and heat dissipation of the anode

anode cooling chart

Hardens the X-ray beam by removing low-energy X-rays

added filtration

What is the discrete spectrum in X-ray emission?

Contains specific values, such as characteristic X-rays

What is the continuous spectrum in X-ray emission?

Contains all possible values, such as bremsstrahlung X-rays

The average energy of the X-ray photons in the beam

effective energy

How does an increase in tube current affect the X-ray emission spectrum?

Increases the amplitude of the spectrum

What is the rule of thumb for kVp and mAs?

A 15% increase in kVp is equivalent to doubling the mAs

What is the effect of added filtration on the X-ray beam?

Reduces quantity but increases average energy

What is the effect of increasing the target atomic number?

Increases both the quality and quantity of X-rays produced

What is the effect of voltage ripple on X-ray beam quality and quantity?

Reduces both quality and quantity

What are the key factors affecting X-ray emission spectra?

Tube current, tube voltage, added filtration, target material, and voltage waveform

How does the target material affect the X-ray spectrum?

Higher atomic number increases efficiency and shifts the spectrum to higher energies

What are the main causes of anode damage in X-ray tubes?

Excessive heat, long exposure times, and single excessive exposures

How does tube voltage affect the X-ray emission spectrum?

Increases both amplitude and position

What is bremsstrahlung radiation commonly referred to as?

"Slowed down" radiation

How is the quantity of X-rays measured?

By the area under the X-ray emission spectrum curve

What is the formula for calculating HU in a three-phase 6-pulse system?

HU = 1.35 × kVp × mA × s

What is the formula for calculating HU in a three-phase 12-pulse system?

HU = 1.41 × kVp × mA × s

What type of X-rays are predominant in the diagnostic range?

Bremsstrahlung X-rays

Why are K-characteristic X-rays important for imaging?

They have fixed energies specific to the target element

What does the stator in the induction motor do?

Produces a magnetic field to rotate the rotor

What happens to the intensity of X-rays on the cathode side due to the anode heel effect?

Intensity is higher on the cathode side

What is the purpose of using a rotating anode?

To distribute heat over a larger surface area

What is the primary interaction for heat production in the anode?

Outer-shell electron excitation and return

How does increasing kVp affect the efficiency of X-ray production?

Efficiency increases with higher kVp

What type of cooling is used to dissipate heat from the housing of an X-ray tube?

Convection cooling

What is the melting point of tungsten used in X-ray tube targets?

3,410°C

What is the main disadvantage of a glass enclosure compared to a metal enclosure?

Shorter tube life and greater likelihood of failure

What does thermionic emission refer to in X-ray tubes?

Electron emission due to heating of the filament

What additional element is mixed with tungsten in filaments to enhance efficiency?

Thorium (1-2%)

What is the principal advantage of a small focal spot in X-ray imaging?

Improved spatial resolution

What determines the effectiveness of the focusing cup?

Its size, shape, charge, filament size, and position

What is the primary source of arcing in X-ray tubes?

Vaporized tungsten depositing on the enclosure

What causes "pitting" in an X-ray tube target?

A single excessive exposure

What is the purpose of a stationary anode in dental and portable X-ray systems?

Used when high tube current and power are not required

What does the rotor do in the induction motor of an X-ray tube?

Rotates the anode

What is the average cooling time for the housing of an X-ray tube?

1-2 hours

What is the limiting factor for small focal spots?

Heat concentration on a smaller area of the target

X-rays emitted through the window of the protective housing

useful beam

How does added filtration affect the characteristic spectrum?

It does not affect the characteristic spectrum

What is the purpose of a heat unit (HU) in X-ray applications?

Measures the heat energy generated during X-ray production

What is the main advantage of using a high-frequency X-ray generator?

Higher efficiency and reduced voltage ripple

What is a "grid-controlled" X-ray tube?

An X-ray tube where the focusing cup acts as an exposure switch

What determines the energy of bremsstrahlung X-rays?

The energy of the projectile electron

What happens to bremsstrahlung X-rays at higher projectile electron energies?

Their maximum energy increases

What is the function of the central ray in X-ray imaging?

It determines the center of the X-ray beam

How does increased target angle affect the effective focal spot?

It increases the size of the effective focal spot

What is the main source of heat in an X-ray tube?

Interactions between outer-shell electrons and the anode

What are the common materials used for rotating anode targets?

Tungsten, molybdenum, and graphite

What is the significance of a high atomic number (Z) in target materials?

Higher Z increases X-ray production efficiency and energy

What is the purpose of the added mechanical strength from rhenium in the target?

To withstand high-speed rotation and thermal expansion/contraction

What does "off-focus radiation" result in?

Reduced image contrast and increased skin dose

What is the effect of decreasing the anode angle on the field size?

The X-ray field size becomes smaller

Why is molybdenum used in the anode stem?

Poor heat conductor to minimize heat transfer to the rotor