Ionising Radiation

    Ionising Radiation
    Which of the statements about radionuclides selected for inclusion in radiopharmaceuticals used in medical imaging is correct? They should:
    Low-energy gamma rays are sufficiently penetrating so that most will pass out of the body and be available for detection, but not so penetrating that they will pass through a “gamma camera” without being detected.
    Author: rikazzz Comment
    Ionising Radiation
    Why does an interventional cardiac angiography procedure have the potential to deliver a high dose of radiation to the patient?
    The long exposure time is the potential problem. All x-ray imaging uses ionising radiation. A radioactive material is not used in cardiac angiography.
    Author: rikazzz Comment
    Ionising Radiation
    Given that the half-value layer of lead for a gamma photon of energy 0.5 MeV is 0.42 cm, which of the situations listed below would result in the LEAST exposure to radiation? Staying in the same room as the gamma source for:
    Choice B would result in 2 × the dose (due to doubling the time), multiplied by 4 × the dose (due to halving the distance) multiplied by ½ × the dose due to the extra half-value layer = 4× the dose of choice A.
    Choice C would result in 3 × the dose multiplied by 1/4 × multiplied by 2 × the dose = 1½ × the dose of choice A.
    Choice D would result in 8 × the dose multiplied by 1 × multiplied by ½ × the dose = 4 × the dose of choice A.
    Author: rikazzz Comment
    Ionising Radiation
    What does the term ionising radiation refer to?
    If the radiation produces ions when it interacts with any substance, then it is ionising radiation. Choice B is true but does not include particulate radiation. Choice C is true but does not include x-rays or cosmic rays.
    Author: rikazzz Comment
    Ionising Radiation
    In an experiment to determine the half-life of a particular radionuclide, measurements of the mass of that nuclide are made. If masses of 8 μg and 2 μg are recorded at intervals of 8 days apart, what is the half-life of the nuclide?
    If we start with 8 μg of a radionuclide and when it decays, it becomes another nuclide, and then after one half-life, there will be 4 μg remaining, and after another half-life, there will be 2 μg. Hence two half-lives have elapsed during the 8-day period. This means one half life is 8 ÷ 2 = 4 days.
    Author: rikazzz Comment
    Ionising Radiation
    Which of the following is a correct use of the unit known as the “electron volt” (eV)?
    The eV is a unit of energy (not radioactivity). It is equal to 1.9 × 10−16 joules of energy. Visible photons have energy of 1.5 eV or less.
    Author: rikazzz Comment
    Ionising Radiation
    What is the purpose of an intensifying screen?
    It converts x-rays (which have high energies but are invisible) into visible light photons. Because visible light photons have low energy, an x-ray photon can be made to produce lots of them.
    Author: rikazzz Comment
    Ionising Radiation
    Conventional radiography – such as a chest x-ray (CXR) – differs from computed tomography (CT) in what respect?
    CT images are unobstructed by the “shadow” of overlying structures.
    Author: rikazzz Comment
    Ionising Radiation
    Which anatomical plane is usually displayed in a nuclear medicine bone scan (a scintigram)?
    A coronal view or a view of the anterior anatomical position is the most common.
    Author: rikazzz Comment
    Ionising Radiation
    The intensity of gamma radiation decreases as the inverse square of the distance. What does this statement mean? If the distance doubles, then the intensity:
    If the distance doubles, the inverse is ½. The square of the inverse is (½)2 = 1/4.
    Author: rikazzz Comment