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    Medical Physics - Alpha Radiation Highly Ionizing: Why is it dangerous?

    Hi, I have not quite fully understood about the harm due to the ionizing affect of alpha particles in medical physics.


    Upon preliminary Google search, I found an article briefly summaries the affect as follow:


    1. cell dies

    2. cell repairs itself

    3. the cell mutates incorrectly and can become cancerous.


    However, the author indicated that not all cells are affected by ionizing radiation in the same way.

    My prior knowledge is that I understand alpha particle can attract electrons in the atoms shell (i.e., ionising atoms in its path). As the alpha reduces its speed, the ionzing becomes stronger as moment = F x change in time.

    My questions are:


    (a) What is the ionizing affect got to do with harming the human body?


    (b) Does the ionizing affect impact on the DNA?


    Look forward to getting a more elaborate explanation.
    Last edited by sassyboy; 12th January 2019 at 23:35.

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    Re: Medical Physics - Alpha Radiation Highly Ionizing: Why is it dangerous?

    "Ionizing" means it breaks a chemical bond (or, many of
    them; alphas are one of the lower dE/dx ions (only protons
    are lower). The broken bond in a target made of meat,
    leaves you with random molecule-fragments. If it
    happened to hit a DNA strand, you just "changed the
    code". Random results, odds of them being beneficial
    are slim. The cell may die, may malfunction, may reproduce
    as-changed but on cue, or may reproduce in some off-
    script way (like malignancy).

    The energy increasing as you approach the Bragg peak
    is not what it's really about. You're talking MeV energies
    and eV per chemical bond, so one 1MeV alpha can bust
    a million-ish bonds. That's rolling a lot of dice with just
    one throw. Snake eyes, one in 11 odds.

    Different cells surely will have different sensitivities to
    getting buck-shot. They all have different "cell guts".
    You'd have to ask a biology type about which ones
    are what way. But, like, your F450 work truck and
    your Ford Focus are both "motor vehicles" but odds
    are the F450 is going to take much more of the same
    abuse, whatever the form.

    X-ray and gamma also play in the same ways, and
    you have a periodic and lifetime dose limits legislated
    based on somebody's idea of acceptable odds. The
    alpha has a lot higher odds of interaction and stops
    in the meat, a few cm in (or less). X-rays and gammas
    mostly pass through low-Z materials (which is why
    they are useful for imaging) without interacting at all,
    although the ones that do can cause the same sort
    of damage. Lower odds and lower dE/dx.



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    Re: Medical Physics - Alpha Radiation Highly Ionizing: Why is it dangerous?

    Our body's cells can repair a minor amount of damage from radiation.

    Of particular concern is our thyroid gland. It is susceptible to accumulating radioactive iodine, with increased threat of ailments or cancer. Potassium iodate/iodide tablets are recommended as a safeguard immediately after exposure (or likelihood of exposure) to radiation.



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    Re: Medical Physics - Alpha Radiation Highly Ionizing: Why is it dangerous?

    It's also worth noting that an alpha (and proton, neutron,
    heavier ion) also impart displacement damage, meaning it
    can knock an atom entirely out of its molecule / lattice
    position (and again, more than one). Lower odds because
    of nuclear vs electron-shell facing area, but almost nil
    chance of restoring the original molecular order; in silicon
    you can get back some knock-offs into the lattice by a
    >300C anneal, but your average meat target is gonna
    be charcoal by that point. Ionized, all you need is the
    electron back (if it wasn't a bonding one, and the bond
    got broken).



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    Re: Medical Physics - Alpha Radiation Highly Ionizing: Why is it dangerous?

    When it comes to X-ray for medical imaging purposes, it is important to mention that, as dick_freebird stated above, part of the emission generated (those of low energy) that does not surpass the human body towards the receiver is useless because they are absorbed by the body, and so they must be eliminated before reach the patient (or rather the 'victim').

    In the case of bulb-based devices, for example, aluminum plates are often used, being the thickness of which proportional to the mass of the part of the body to be x-rayed, and is tabulated to turn easy the choice of the suited plate for each case. These plates have to be affixed to the front side of the equipment head, being easily distinguishable the groove where these plates have to be coupled; that is, when being X-rayed, instead of one seeing a glass surface, one would be seeing a metal surface.

    However, it is notable that, at least here where I live, a significant part of the radiographic operators, do not use such accessories, and some of them do not even know what the purpose of such parts.
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