Ionising Radiation

    Ionising Radiation
    Which statement about the differences between medical imaging using x-rays and a nuclear medicine scan using gamma rays is correct?
    X-rays that pass through the body without being absorbed by the body are used to produce an image of internal structure. In nuclear medicine, a radioactive material is incorporated into the body and travels to certain organs from where a gamma ray is emitted. If physiology is altered sufficiently to affect the way the radioactive material moves about the body, the resulting image provides information about how much alteration there has been.
    Author: rikazzz Comment
    Ionising Radiation
    Why are radioactive isotopes of the stable elements that occur normally in the body useful for tracing metabolic pathways? Because:
    Radioactive forms of elements that occur naturally in the body will be handled by the body in exactly the same way as the non-radioactive isotope. Hence their location within the body can be traced by the gamma radiation they emit.
    Author: rikazzz Comment
    Ionising Radiation
    Of the following, which one would be considered the lowest level for a fatal whole-body dose of radiation if received as an acute dose?
    Ten sievert acutely is a lethal dose. 100R is close to 1Sv dose to soft tissue. Both 10 mSv and probably also 100 mSv would produce no noticeable effect on the body.
    Author: rikazzz Comment
    Ionising Radiation
    To what energy can an x-ray tube that is operated at 110 kV accelerate electrons?
    An electron volt is the amount of energy gained by an electron when it is accelerated by a potential difference of 1 volt. 110 keV is the amount of energy gained by an electron when it is accelerated by a potential difference of 110 kilovolt.
    Author: rikazzz Comment
    Ionising Radiation
    Why is it possible to trace metabolic pathways in the body using radioactive isotopes of the naturally occurring elements in the body? Because radioactive isotopes:
    Radioactive forms of elements that occur naturally in the body will be chemically handled by the body in exactly the same way as the non-radioactive isotope. Hence their location within the body can be traced by the gamma radiation they emit.
    Author: rikazzz Comment
    Ionising Radiation
    The “half-value layer” for gamma rays of 0.5 MeV is 0.42 cm of lead. What percentage of the original ray would penetrate four half-value layers?
    Four half-value layers would absorb all but ½ × ½ × ½ × ½ = 1/16 (6.25%) of the photons.
    Author: rikazzz Comment
    Ionising Radiation
    The term “radioactive” when applied to the nucleus of an atom refers to which one of the following phenomena?
    Choice B is wrong as x-rays don’t come from a nucleus. Choice C is wrong as sometimes a nucleus is in an “excited” state and returns to ground state by emitting a gamma ray while the nuclear structure is unchanged. Choice D is wrong as a nucleus which has the optimum ratio of neutrons to protons is not unstable.
    Author: rikazzz Comment
    Ionising Radiation
    Why are gamma rays able to penetrate “solid” walls but alpha or beta rays cannot? Because:
    It is the absence of an electrical charge that allows photons to pass by electrons and atomic nuclei with being attracted or repelled by them. This means that photons are undeflected unless they suffer a direct hit.
    Author: rikazzz Comment
    Ionising Radiation
    What may the term radioactivity correctly used to refer to?
    Unstable nucleus = radioactive. Choices A and C also describe radioactivity but not in as general terms as choice B.
    Author: rikazzz Comment
    Ionising Radiation
    Why is an absorbed radiation dose of 10 grays absorbed over 1 day (i.e. acutely) more damaging to living tissue than the same dose received as 1000 exposures of 0.01 grays over 10 years (i.e. chronically)?
    There are repair mechanisms within a cell that can repair radiation damage, given time and damage that is not too severe.
    Author: rikazzz Comment