Radiographic Imaging Principles
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What is the name given to photons that strike the image receptor after interacting with atoms in the patient?

  • Direct transmission photons
  • Attenuated photons
  • Indirect transmission photons (correct)
  • Transmitted photons

    • What kind of interaction between photons and atoms leads to the removal of the photon?

  • Absorption (correct)
  • Scatter
  • Refraction
  • Reflection

    • Which of the following is NOT a characteristic of attenuated photons?

  • They contribute to the formation of the image. (correct)
  • They do not strike the image receptor.
  • They have the same energy as incident photons.
  • They may have undergone absorption or scatter.

    • What type of scatter is described as having a minimal change in the photon's path and energy?

    <p>Small-angle scatter (C)</p> Signup and view all the answers

    Which event would cause a photon to be considered 'attenuated'?

    <p>Both B and C (D)</p> Signup and view all the answers

    What is the term used to describe the photons that reach the image receptor without interacting with the patient?

    <p>Direct transmission photons (C)</p> Signup and view all the answers

    Which of the following would be considered an example of indirect transmission?

    <p>A photon that interacts with an atom and changes direction slightly, still reaching the image receptor. (B)</p> Signup and view all the answers

    Which of the following best describes the effect of small-angle scatter on a radiographic image?

    <p>Reduced image sharpness (A)</p> Signup and view all the answers

    Which of the following accurately describes the effect of X-rays interacting with biological tissue?

    <p>X-ray interactions with tissue result in absorption, scattering, and transmission. (D)</p> Signup and view all the answers

    What is the primary reason why the absorption of X-rays by various body structures is essential for producing diagnostic images?

    <p>Absorption allows for the creation of a visible shadow on the film, highlighting dense structures. (B)</p> Signup and view all the answers

    Why is it beneficial for the patient's radiation dose to be minimal?

    <p>Minimal dose reduces the risk of potential harm to the patient from radiation exposure. (A)</p> Signup and view all the answers

    What is the primary material used for the target in a diagnostic X-ray tube, and why?

    <p>Tungsten, because it has a high melting point and can withstand the high temperatures during X-ray production. (B)</p> Signup and view all the answers

    Which of the following statements about X-ray production is incorrect?

    <p>The energy of the produced X-rays is determined by the type of material used for the target. (A)</p> Signup and view all the answers

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

    <p>The filament serves as a source of electrons for the X-ray beam. (C)</p> Signup and view all the answers

    Why is it important to minimize the scatter radiation in X-ray imaging?

    <p>All of the above. (D)</p> Signup and view all the answers

    What is the primary reason for the use of a highly evacuated glass tube in X-ray production?

    <p>To minimize electron collisions with air molecules, ensuring efficient electron beam production. (D)</p> Signup and view all the answers

    How does the density of air compare to the density of soft tissue?

    <p>Air is approximately 1000 times less dense than soft tissue. (D)</p> Signup and view all the answers

    What is the relationship between the amount of radiation absorbed by a material and the appearance of that material on a digital detector image?

    <p>The more radiation absorbed, the darker the image. (A)</p> Signup and view all the answers

    What is the main reason why bone appears brighter than soft tissue on a radiographic image?

    <p>All of the above. (D)</p> Signup and view all the answers

    What does the term 'effective atomic number' (Z_eff) refer to?

    <p>The average atomic number of all the elements in a material. (A)</p> Signup and view all the answers

    If a material has a higher effective atomic number (Z_eff), what is the likely effect on its attenuation of X-ray photons?

    <p>The material will absorb more X-ray photons. (B)</p> Signup and view all the answers

    In the context of X-ray imaging, what does the term 'attenuation' refer to?

    <p>All of the above. (D)</p> Signup and view all the answers

    Based on the provided information, how many times more photons are absorbed by bone compared to soft tissue, given equal thickness?

    <p>13 times more. (A)</p> Signup and view all the answers

    Why is the density of a material relevant when considering its attenuation of X-ray photons?

    <p>Denser materials have more atoms per unit volume, leading to more interactions with photons. (C)</p> Signup and view all the answers

    What is the name given to the process in which an incoming x-ray photon interacts with the electric field surrounding the nucleus of an atom, causing it to disappear and convert its energy into matter?

    <p>Pair production (B)</p> Signup and view all the answers

    Which of the following accurately describes the particles created during pair production?

    <p>One electron and one positron (D)</p> Signup and view all the answers

    How does pair production differ from Compton scattering?

    <p>Pair production involves the absorption of the incoming photon, while Compton scattering only alters its direction and energy. (B)</p> Signup and view all the answers

    What is the significance of the electric field surrounding the nucleus in pair production?

    <p>It provides the necessary energy for the photon to be absorbed and transformed into matter. (C)</p> Signup and view all the answers

    Why is pair production not relevant to diagnostic radiology, according to the text?

    <p>Diagnostic radiology utilizes x-rays with energies lower than the threshold required for pair production. (B)</p> Signup and view all the answers

    What is the primary reason for including a description of pair production in the text, despite its irrelevance to diagnostic radiology?

    <p>To provide a comprehensive overview of all possible interactions of x-radiation with matter. (D)</p> Signup and view all the answers

    Which of the following statements best describes the importance of Compton scattering in diagnostic imaging?

    <p>Compton scattering contributes to the scattered radiation that degrades image quality in diagnostic radiology. (C)</p> Signup and view all the answers

    Why is Compton scattering considered important in the energy range used in diagnostic radiology?

    <p>Because it is a significant contributor to the scattered radiation that can degrade image quality. (D)</p> Signup and view all the answers

    Which radiation interaction is commonly referred to as a "modified scattering" interaction?

    <p>Compton Scattering (A)</p> Signup and view all the answers

    What is the primary reason why coherent scattering is not significant in diagnostic radiology?

    <p>Its occurrence is extremely rare at diagnostic energies. (D)</p> Signup and view all the answers

    At which energy range does coherent scattering occur most frequently, as stated in the text?

    <p>Less than 10 keV (D)</p> Signup and view all the answers

    What is the primary characteristic distinguishing coherent scattering from Compton scattering?

    <p>The energy of the scattered photon in relation to the incident photon. (D)</p> Signup and view all the answers

    Which radiation interaction plays a significant role in both diagnostic and therapeutic radiology?

    <p>Compton Scattering (C)</p> Signup and view all the answers

    What is the primary reason why photoelectric absorption is prominently used in diagnostic radiology?

    <p>It results in the emission of characteristic x-rays, contributing to image formation. (D)</p> Signup and view all the answers

    What is the primary reason why pair production is primarily utilized in therapeutic radiology?

    <p>It generates high-energy electrons which can destroy cancer cells. (B)</p> Signup and view all the answers

    Which of the following interactions is NOT considered significant for therapeutic radiology?

    <p>Coherent Scattering (B)</p> Signup and view all the answers

    The Compton interaction is not suitable for contrast imaging because it is _________ dependent.

    <p>atomic number (Z) (B)</p> Signup and view all the answers

    In diagnostic radiography, as the energy of the x-ray photon increases, what happens to the probability of Compton scattering occurring relative to the photoelectric effect?

    <p>It increases. (D)</p> Signup and view all the answers

    Why is the Compton interaction considered a potential health hazard for imaging personnel?

    <p>The scattered photons can exit the patient and increase occupational radiation exposure. (B)</p> Signup and view all the answers

    What effect do Compton scattered photons have on the radiographic image?

    <p>Decreased contrast by adding unwanted exposure, known as radiographic fog. (D)</p> Signup and view all the answers

    Which interaction has an energy dependence that decreases more slowly with increasing energy than the photoelectric interaction?

    <p>Compton scattering (B)</p> Signup and view all the answers

    What is the primary contributor to image contrast in diagnostic radiology?

    <p>Photoelectric effect (D)</p> Signup and view all the answers

    Which of the following statements regarding Compton scattering is TRUE?

    <p>It is the dominant interaction at low energies. (D)</p> Signup and view all the answers

    What is the primary reason why Compton scattering is less significant in therapeutic energies than diagnostic energies?

    <p>The photoelectric effect becomes more dominant at therapeutic energies. (D)</p> Signup and view all the answers

    Study Notes

    Interaction of X-Radiation With Matter

    • Fundamental physics concepts related to radiation interaction and scatter are crucial for radiographers in selecting technical factors like kVp (peak kilovoltage) and mAs (milliampere-seconds)
    • kVp controls the quality (penetrating power) and to some extent the quantity of x-ray photons in the beam.
    • mAs controls the quantity of photons in the x-ray beam.
    • X-rays can interact with biological tissue in three ways: absorption, scattering, and passing through without interaction.
    • Absorption is the transfer of x-ray energy to the biological tissue atoms.
    • The amount of energy absorbed per unit mass is the absorbed dose (D).
    • Scatter occurs when x-rays interact with tissue atoms and change direction.
    • Direct transmission refers to photons that pass through the patient without interaction, while indirect transmission happens when photons interact, are scattered, but still hit the image receptor.
    • Attenuation encompasses both absorption and scatter, preventing photons from reaching the image receptor. Attenuation is reduction in the intensity of the primary photon beam either from absorption or scatter.
    • Primary radiation refers to the x-ray photons produced in the x-ray tube.
    • Exit radiation or image-formation photons strike the image receptor.
    • Attenuated photons are those that do not reach the image receptor because they were absorbed or scattered.
    • All scatter does not result in indirect transmission.

    X-Ray Beam Production and Energy

    • Diagnostic x-ray beams are produced by a stream of high-energy electrons bombarding a positively charged target (anode).
    • Tungsten or tungsten alloys are commonly used for the anode target due to their high melting points and high atomic numbers.
    • X-ray photons are produced as electrons interact with the target atoms.
    • X-ray photons have a spectrum of energies.
    • The maximum energy of x-ray photons equals the energy of the electrons bombarding the target, measured in kilovolts peak (kVp).
    • The filtered x-ray photon beam is referred to as primary radiation.
    • Inherent filtration is the combination of the x-ray tube glass wall and additional aluminum placed within the collimator assembly.
    • X-ray photons can have no more energy than the electrons striking the anode/target.

    Direct and Indirect Transmission X-Ray Photons

    • X-rays pass through the patient and interact to create an image.
    • Direct transmission photons pass through without interaction.
    • Indirect transmission photons interact with tissue but still strike the image receptor.
    • Indirect transmission is always a result or scatter.

    Attenuation

    • Attenuation is the reduction in the intensity of the primary photon beam.
    • Attenuation can either be from absorption or scattering.
    • Absorption happens when photons lose all their energy when interacting with a tissue atom.
    • Scatter happens when photons lose part of their energy and are redirected.

    Probability of Photon Interaction With Matter

    • Photon interactions with matter are random.
    • The probability of interaction can be predicted on average for a large number of photons
    • Interaction characteristics are described in tables.
    • The probability of interactions varies greatly depending on atomic number and energy of x-ray photons.

    Processes of Interaction

    • Five types of x-ray interactions are possible:
      • Coherent scattering
      • Photoelectric absorption
      • Compton scattering
      • Pair production
      • Photodisintegration

    Coherent Scattering

    • Involves no energy loss, only a change in direction.
    • Important at low energies.

    Photoelectric Absorption

    • Most important mode of x-ray interaction for radiographic imaging.
    • X-ray photon gives all its energy to an inner-shell electron, causing its ejection (photoelectron).
    • This creates a vacancy, which is filled by an outer-shell electron, emitting characteristic x-ray.
    • More likely in materials with higher atomic numbers and lower photon energies.
    • Probability is proportional to Z3/E3 ( where Z is atomic number and E is energy.

    Compton Scattering

    • Incoming photons interact with loosely bound outer shell electrons.
    • Photon energy is transferred, resulting in a scattered photon and Compton scattered electron, with a changed trajectory.
    • Important source of scattered radiation in diagnostic radiology.

    Pair Production

    • Occurs at high photon energies (greater than 1.022 MeV).
    • Photon energy is converted into matter in the form of electron-positron pair.
    • Important at high energies.

    Photodisintegration

    • Occurs at very high energies (greater than 10 MeV)..
    • Photon energy is completely absorbed by the nucleus causing its instability.
    • This can lead to emission of particles (neutrons, protons, or alpha particles.)
    • Not important in ordinary diagnostic radiology.

    Mass Density and Effective Atomic Number

    • Different body structures have different densities and atomic numbers.
    • Density and atomic number influence attenuation.
    • High density/atomic number structures attenuate x-rays more than low density/atomic number structures.
    • X-ray absorption depends on both thickness and characteristics of the tissue.
    • Tissue with greater density and atomic number appear darker in radiographs.

    Use of Contrast Media

    • Contrast media have higher atomic numbers than surrounding tissue
    • They enhance visualization of specific structures.
    • Positive contrast media (e.g., barium, iodine) appear brighter on radiographs because they absorb x-rays more readily.
    • X-ray absorption is greater due to higher Z-number.

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    Description

    Test your understanding of key concepts in radiographic imaging. This quiz covers topics such as photon interactions, attenuation, and scatter. Assess your knowledge of how X-rays interact with biological tissues to produce diagnostic images.

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