Unit 1 Attenuation Coefficients - Med Rad 2
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Questions and Answers

What is the primary reason radiologic contrast agents are used in imaging?

  • To reduce the effect of Compton scatter
  • To decrease the photon energy
  • To increase the intensity of the x-ray beam
  • To enhance the differential absorption of certain tissues and organs (correct)

    • What is the main difference between absorption and attenuation?

  • Absorption is the effect of x-rays on soft tissue, while attenuation is the effect on bone
  • Absorption is the scattering of x-rays, while attenuation is the reduction of intensity
  • Absorption is the reduction of x-ray intensity, while attenuation includes scattering (correct)
  • Absorption is the effect of x-rays on bone, while attenuation is the effect on soft tissue

    • What is the significance of atomic number and mass density of tissue on differential absorption?

  • They decrease the differential absorption of x-rays
  • They have no effect on differential absorption
  • They increase the differential absorption of x-rays (correct)
  • They are only relevant in polychromatic beams

    • What is the purpose of the midterm and final exams in RADL 3010?

    <p>To evaluate student understanding of the first and second half of the course</p> Signup and view all the answers

    What is the difference between monochromatic and polychromatic beams in terms of attenuation?

    <p>Monochromatic beams have a single energy, while polychromatic beams have a range of energies</p> Signup and view all the answers

    What is the probability of PE effect and Compton scatter dependent on?

    <p>Photon energy, atomic number, and density</p> Signup and view all the answers

    What is the term used to describe the reduction of photons or weakening of the primary beam following penetration through a given thickness?

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

    What occurs when an X-ray or gamma ray beam interacts with atomic particles in matter?

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

    What is the energy transferred to the ejected electron in Compton Scattering?

    <p>Kinetic energy</p> Signup and view all the answers

    What is the mathematical equation for Compton Scattering?

    <p>EP = ES + EB + EKE</p> Signup and view all the answers

    What is the energy of the Compton scattered photon in the given example?

    <p>34.5 kV</p> Signup and view all the answers

    What happens to the scattered photon as it travels through matter?

    <p>It loses energy</p> Signup and view all the answers

    What is the probability of Compton scattering dependent on?

    <p>Energy of the incident x-ray</p> Signup and view all the answers

    What is the result of Compton scattering in radiography?

    <p>Scattered x-rays provide no useful information</p> Signup and view all the answers

    What is the term used to describe the energy transferred to the matter as the beam passes through?

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

    What type of scattering is described in the passage?

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

    What is the primary source of occupational radiation exposure received by radiographers?

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

    What happens to the energy of the x-ray photon in a photoelectric interaction?

    <p>It is absorbed by the inner shell electron</p> Signup and view all the answers

    What is the energy of the photoelectron ejected from a calcium atom, if the electron binding energy is 4 kV and the incident x-ray energy is 30 kV?

    <p>26 kV</p> Signup and view all the answers

    What is the relationship between the probability of a photoelectric interaction and the incident x-ray energy?

    <p>The probability decreases as the energy increases</p> Signup and view all the answers

    What is the relationship between the probability of a photoelectric interaction and the atomic number of the absorbing material?

    <p>The probability is directly proportional to the third power of the atomic number</p> Signup and view all the answers

    What is the effect of Compton scattering on image contrast?

    <p>It decreases image contrast</p> Signup and view all the answers

    What happens to the photoelectron ejected from an atom in a photoelectric interaction?

    <p>It escapes with kinetic energy</p> Signup and view all the answers

    What is the purpose of the binding energy in a photoelectric interaction?

    <p>To eject the electron from its orbit</p> Signup and view all the answers

    What is the comparison of the probability of a photoelectric interaction between an 80 keV x-ray and fat (Z = 6.3) and barium (Z = 56) compared with soft tissue (Z = 7.4)?

    <p>Fat has a lower probability, barium has a higher probability</p> Signup and view all the answers

    What is the effect of photoelectric absorption on the final image?

    <p>It is not related to the image</p> Signup and view all the answers

    What is the result of an x-ray ejecting a K-shell electron from an atom?

    <p>An orbital vacancy is created, resulting in an unstable state.</p> Signup and view all the answers

    What is the energy of the characteristic x-ray emitted when an outer shell electron drops into the vacancy created by the ejection of a K-shell electron?

    <p>The difference between the binding energies of the shells involved.</p> Signup and view all the answers

    What happens to the x-rays that undergo photoelectric absorption in the body?

    <p>They are completely absorbed by the body.</p> Signup and view all the answers

    What is the significance of characteristic x-rays in radiology?

    <p>They have no effect on the final radiographic image.</p> Signup and view all the answers

    What is the difference between radiopaque and radiolucent structures?

    <p>Radiopaque structures absorb x-rays, while radiolucent structures transmit them.</p> Signup and view all the answers

    How does the selection of kVp affect the differential absorption of x-rays?

    <p>Decreasing kVp increases differential absorption.</p> Signup and view all the answers

    What is the relationship between the probability of photoelectric absorption and the atomic number of the tissue?

    <p>The probability is proportional to the third power of the atomic number.</p> Signup and view all the answers

    How does the energy of the incident x-ray affect the probability of photoelectric absorption and Compton scattering?

    <p>Both probabilities decrease with increasing energy.</p> Signup and view all the answers

    What is the effect of Compton scattering on image contrast?

    <p>Compton scattering decreases image contrast.</p> Signup and view all the answers

    What is the result of a compromise between image contrast and patient dose in radiology?

    <p>Lower image contrast and higher patient dose.</p> Signup and view all the answers

    What is the total mass attenuation coefficient a result of?

    <p>Various absorption and scattering processes</p> Signup and view all the answers

    What is the symbol that represents the component of total linear attenuation coefficient due to the photoelectric effect?

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

    How does the probability of a photoelectric effect change with the atomic number of the absorbing material?

    <p>It is directly proportional to the third power of the atomic number</p> Signup and view all the answers

    What is the general trend of the value of μ with increasing energy of the incident beam?

    <p>It decreases</p> Signup and view all the answers

    Which of the following materials has a higher μ value at a given X-ray energy?

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

    How does the value of σ/ρ change with increasing X-ray energy?

    <p>It decreases</p> Signup and view all the answers

    What does the mass density of a tissue affect?

    <p>The number of electrons available for interaction</p> Signup and view all the answers

    Why do Barium and Iodine compounds have a much higher atomic number and mass density than soft tissue?

    <p>Because they have a higher number of electrons and are densely packed</p> Signup and view all the answers

    What is the result of dividing the total linear attenuation coefficient by its density?

    <p>The mass attenuation coefficient</p> Signup and view all the answers

    What is the binding energy of the K shell electron for Barium?

    <p>37.4 keV</p> Signup and view all the answers

    What happens to the probability of x-ray interaction when the mass density of a tissue is doubled?

    <p>It is doubled</p> Signup and view all the answers

    Why do x-rays interact more with bone than with soft tissue?

    <p>Because bone has a higher mass density</p> Signup and view all the answers

    What is the unit of the total linear attenuation coefficient?

    <p>m-1</p> Signup and view all the answers

    What is the main difference between the total linear attenuation coefficient and the mass attenuation coefficient?

    <p>The total linear attenuation coefficient takes into account density, while the mass attenuation coefficient does not</p> Signup and view all the answers

    What happens to Compton scattering as x-ray energy increases?

    <p>It decreases slowly</p> Signup and view all the answers

    What is the purpose of using contrast agents in radiologic imaging?

    <p>To enhance differential absorption in homogeneous tissue</p> Signup and view all the answers

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