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Nuclear Medicine and Radiation Safety: Flashcards

Revise becquerels, grays and sieverts, tracers, PET, radiotherapy and protection by time, distance and shielding.

10 cardsIntermediate

10 cards

  1. Question
    What is ionizing radiation, and how does it harm cells?
    Answer

    Radiation that knocks electrons out of atoms. It breaks bonds in DNA directly or forms damaging free radicals from water.

  2. Question
    Becquerel, gray, sievert?
    Answer

    Bq = decays per second (activity). Gy = J absorbed per kg (absorbed dose). Sv = Gy × weighting factor (equivalent dose).

  3. Question
    Radiation weighting factors?
    Answer

    1 for gamma, X-rays and beta; 20 for alpha.

  4. Question
    What makes a good imaging isotope?
    Answer

    Gamma emitter, short half-life (hours), can be targeted to an organ. Example: technetium-99m (6.01 h).

  5. Question
    Why are alpha emitters not used for imaging?
    Answer

    Alpha particles do not leave the body, so they cannot be detected outside, and they give a high local dose.

  6. Question
    How does a PET scan detect fluorine-18?
    Answer

    Its positron annihilates with an electron, giving two 511 keV gamma rays in opposite directions, recorded by a detector ring.

  7. Question
    Name a radioisotope used to treat the thyroid.
    Answer

    Iodine-131 (beta and gamma, 8.02 d): the thyroid takes up iodine, and the beta particles destroy the tissue.

  8. Question
    Three ways to reduce radiation dose?
    Answer

    Less time, more distance, more shielding (and keep doses as low as reasonably achievable).

  9. Question
    Inverse-square law?
    Answer

    Dose rate ∝ 1 ÷ distance²: doubling the distance cuts the rate to one-quarter.

  10. Question
    Average natural background dose?
    Answer

    About 2.4 mSv per year worldwide, mostly from radon, rocks, cosmic rays and food.