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Radiation Therapy Dosimetry and Quality Assurance
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Radiation Therapy Dosimetry and Quality Assurance

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Questions and Answers

What is the purpose of using a tissue equivalent phantom in isodose measurement?

  • To move ionization chambers within the phantom
  • To measure the dose at a specific depth
  • To absorb the X-ray beam
  • To determine the dose distribution in a specific patient volume (correct)
  • What is the characteristic of the material used to make the phantom?

  • It has the same density as wood
  • It has the same atomic number, electron density, and density as tissue (correct)
  • It has the same atomic number as air
  • It has the same electron density as metal
  • What is the advantage of using higher energy X-rays in radiotherapy?

  • Increased Compton scattering
  • Increased skin damage
  • Better defined beam edges (correct)
  • Increased absorption by the tissue
  • What is the relationship between the photon energy and the depth of the peak dose?

    <p>The depth of the peak is roughly a quarter of the photon energy in megavolts</p> Signup and view all the answers

    What is the typical range of the surface dose for most teletherapy units?

    <p>20–50%</p> Signup and view all the answers

    What does the physician do with the plan of the medical physicist?

    <p>Verifies and approves the plan for use</p> Signup and view all the answers

    Why does the beam enter the skin at an angle other than 90â—¦?

    <p>Because the skin is curved</p> Signup and view all the answers

    What is used at higher energies to correct the dose distribution?

    <p>Mathematical corrections</p> Signup and view all the answers

    What is the purpose of collimators in LINAC planning?

    <p>To spare sensitive organs</p> Signup and view all the answers

    What is plotted on the anatomy during LINAC planning?

    <p>Isodose curves</p> Signup and view all the answers

    What is the volume that has to be treated called?

    <p>Treated volume</p> Signup and view all the answers

    What is the minimum dose difference required between the treated volume and elsewhere?

    <p>20%</p> Signup and view all the answers

    What is the purpose of using multiple beams in treatment planning?

    <p>To conform the radiation to the treatment volume</p> Signup and view all the answers

    What is the role of a Medical Physicist in LINAC planning?

    <p>All of the above</p> Signup and view all the answers

    What is the primary purpose of a CT scan in LINAC planning?

    <p>To guide the radiation therapy</p> Signup and view all the answers

    What is the primary purpose of a treatment simulator in radiation therapy?

    <p>To provide information on the treatment area for planning and verify patient positioning</p> Signup and view all the answers

    What is the function of multileaf collimators in IMRT?

    <p>To shape the radiation beam and modulate the beam intensity</p> Signup and view all the answers

    Why is patient positioning crucial in radiation therapy?

    <p>To ensure accurate delivery of radiation beams</p> Signup and view all the answers

    What is the purpose of a patient shell in radiation therapy?

    <p>To position the patient correctly during treatment</p> Signup and view all the answers

    What aspect of quality assurance is involved in ensuring the proper functioning of new equipment?

    <p>Commissioning of new equipment</p> Signup and view all the answers

    What is the main reason for the dose to fall with depth in a tissue?

    <p>Due to the absorption of the beam by the tissue</p> Signup and view all the answers

    What is the purpose of plotting the dose distribution in the form of isodose charts?

    <p>To determine the dose at a specific patient volume</p> Signup and view all the answers

    What is the effect of Compton scattering on the beam at low energies?

    <p>It leads to the diffuse edges of the beam</p> Signup and view all the answers

    What is the characteristic of the isodose lines?

    <p>They are lines of constant dose</p> Signup and view all the answers

    What is the most penetrating beam used in external beam radiotherapy?

    <p>150 MeV proton beam</p> Signup and view all the answers

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