Oral radiology lecture 1
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Questions and Answers

What is the speed of light (c)?

  • Weightless photons
  • 0.01 – 0.001 nm
  • 3 x 10^8 m/s (correct)
  • No electrical charge

    • What happens to the energy of x-ray photons as the wavelength gets shorter or the frequency gets higher?

  • The energy becomes negative
  • The energy increases (correct)
  • The energy remains the same
  • The energy decreases

    • How are x-rays generated in an x-ray tube?

  • By magnetic induction
  • By energy conversion when fast-moving electrons are suddenly decelerated (correct)
  • By gravitational force
  • By nuclear fusion reactions

    • What are the essential requirements for the generation of x-rays?

    <p>A source of electrons, a potential to accelerate them at high speeds, a target upon which the electrons can impact and a vacuum to maximize production</p> Signup and view all the answers

    What must be present to maximize the production of x-rays?

    <p>A vacuum</p> Signup and view all the answers

    What is the speed of light equal to?

    <p>Wavelength times frequency</p> Signup and view all the answers

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

    <p>To reflect electrons to a narrow beam toward the anode</p> Signup and view all the answers

    What is the primary purpose of the target in the anode of the X-ray tube?

    <p>To convert kinetic energy of electrons from the cathode into x-rays</p> Signup and view all the answers

    What happens as the size of the focal spot in the target decreases?

    <p>The sharpness of the image increases, but the capability to absorb heat decreases</p> Signup and view all the answers

    What is the material used to make the filament in the cathode?

    <p>Tungsten</p> Signup and view all the answers

    Which type of anode is better with heat dissipation in an X-ray tube?

    <p>Rotating anode</p> Signup and view all the answers

    What is the primary purpose of the filament in the cathode of an X-ray tube?

    <p>To provide the source of electrons made of tungsten</p> Signup and view all the answers

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

    <p>To serve as a negative charged concave reflector made of molybdenum</p> Signup and view all the answers

    What happens to the majority of the kinetic energy in an X-ray tube?

    <p>Dissipates as heat through the copper stem</p> Signup and view all the answers

    What is the function of the step-down transformer in the power supply of an X-ray machine?

    <p>To reduce the voltage from 110V to about 10V at the filament</p> Signup and view all the answers

    What does the autotransformer do in the power supply of an X-ray machine?

    <p>Converts primary voltage from the input source into the second voltage</p> Signup and view all the answers

    What is the purpose of the mA switch in an X-ray machine?

    <p>To control the tube current in milliamperes</p> Signup and view all the answers

    What does the timer control in an X-ray machine?

    <p>The duration of x-ray exposure</p> Signup and view all the answers

    How is the timer calibrated in an X-ray machine?

    <p>In fractions and whole numbers of seconds</p> Signup and view all the answers

    What is the equivalent of 1 second in terms of number of impulses for the X-ray exposure?

    <p>60 impulses</p> Signup and view all the answers

    What is the primary cause of Bremsstrahlung radiation?

    <p>Electrostatic attraction on the electron due to its proximity to the nucleus</p> Signup and view all the answers

    What describes the energy of the x-ray beam produced by dental x-ray units in bremsstrahlung radiation?

    <p>Described by identifying the peak operating voltage in kVp</p> Signup and view all the answers

    What is the source of most x-rays produced by dental x-ray units?

    <p>Bremsstrahlung radiation</p> Signup and view all the answers

    Which radiation has a continuous spectrum of energy?

    <p>Bremsstrahlung radiation</p> Signup and view all the answers

    What causes characteristic radiation to be given off?

    <p>Ejection of an inner orbital electron from a tungsten target atom</p> Signup and view all the answers

    What is the primary cause of characteristic radiation in an X-ray tube?

    <p>Filling of a vacancy in the orbit</p> Signup and view all the answers

    Which type of radiation has a continuous spectrum of energy?

    <p>Bremsstrahlung radiation</p> Signup and view all the answers

    What is the primary characteristic of characteristic radiation in an X-ray tube?

    <p>It has a minor source of radiation from the x-ray tube</p> Signup and view all the answers

    What is the primary cause of Bremsstrahlung radiation in an X-ray tube?

    <p>Collisions between electrons and the anode target material</p> Signup and view all the answers

    Study Notes

    Speed of Light

    • Speed of light (c) is approximately 299,792 kilometers per second (or 186,282 miles per second).

    X-Ray Photon Energy

    • As the wavelength of x-ray photons decreases, their energy increases.
    • Higher frequency corresponds to higher energy in x-ray photons.

    Generation of X-Rays

    • X-rays are generated in an x-ray tube when high-speed electrons collide with a target material.
    • Essential requirements for x-ray generation include a vacuum environment, a filament to produce electrons, and a target for electron collision.

    Maximizing X-Ray Production

    • To maximize x-ray production, a high atomic number target material is necessary, such as tungsten.
    • Sufficient potential difference in the tube and proper electron focus are crucial.

    Focusing Cup and Anode Target Function

    • The focusing cup directs electrons toward the target, increasing x-ray output efficiency.
    • The target of the anode converts kinetic energy from electrons into x-rays through interactions with the target material.

    Focal Spot Size

    • As the focal spot size decreases, spatial resolution improves, allowing for clearer imaging.

    Material and Design of the Cathode

    • The filament in the cathode is typically made from tungsten due to its high melting point and durability.
    • A rotating anode design is superior for heat dissipation in an x-ray tube, preventing damage from prolonged exposure.

    Function of Components in the X-Ray Tube

    • The filament in the cathode heats up to produce electrons through thermionic emission.
    • The step-down transformer reduces voltage to heat the filament effectively.
    • An autotransformer in the power supply adjusts the voltage to necessary levels for optimal x-ray production.

    Controls in X-Ray Machines

    • The mA switch controls the quantity of x-rays produced by adjusting the filament current.
    • The timer regulates the duration of x-ray exposure; it is often calibrated in impulses.

    Bremsstrahlung and Characteristic Radiation

    • Bremsstrahlung radiation is primarily caused by high-speed electrons being deflected by atomic nuclei, producing x-rays with a continuous spectrum of energy.
    • The majority of x-rays generated in dental units arise from bremsstrahlung radiation.
    • Characteristic radiation occurs when electrons eject inner-shell electrons from target atoms, leading to the emission of x-rays with specific energies.

    Key Characteristics

    • Characteristic radiation has distinct energy levels and is generated when outer-shell electrons fill inner-shell vacancies.
    • Bremsstrahlung radiation provides a continuous energy spectrum due to variable energy interactions.

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    Test your knowledge about the fundamental concepts of X-ray radiation, including speed, wavelength, frequency, and energy of X-rays.

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