15
Dec
09

CT scans equivalent to about 100 chest X-rays

Following on from my article about X Ray machines at airports being intrusions into our privacy and potential cancer risks I read an article in the L.A. Times today that says that CT scans may be even more of a risk.

while a normal CT scan of the chest is the equivalent of about 100 chest X-rays, the team found that some scanners were giving the equivalent of 440 conventional X-rays. The absolute risk may be small for any single patient, but the sheer number of CT scans — more than 70 million per year, 23 times the number in 1980 — will produce a sharp increase in cancers and deaths, experts said.”

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6 Responses to “CT scans equivalent to about 100 chest X-rays”


  1. February 24, 2010 at 1:17 am

    With every medical X-ray exposure be it plain film X-ray Computed Tomography, Radionuclide Imaging or Operating theatre screening there is a radiation dose, as you have discussed there is a somatic risk that radiation may cause cancer. However there is a risk Vs benefit process in which a professionally qualified person or persons normally a Radiographer and in the case of high dose procedures also a radiologist filter out requests where the dose is likely to be more of a risk than the medical condition that the patient is seeking diagnosis for. Whilst a CT scan of the Thoracic cavity does have a dose of approximately 75 cGy where as the dose for a chest X-ray is approx 8 cGy I have seen chest X-rays with doses up to 22 cGy for larger people. either way its is wrong to compare these as like for like as a chest xray gives a two dimensional representation of the lungs and mediastinum. Generally if a person is having a thoracic CT scan there is a reason for at. examples would be such things as diagnosing lung cancer and locating carcinoma in the lungs to prepare for radio/chemo therapy or plotting exact images of the heart and associated arteries and veins prior to surgery, whilst there is no level of radiation which is totally safe the likelihood of getting a cancerous growth from this procedure is less than 1 in 3000. The likelihood of a patient with suspected lung cancer becoming inoperable and terminal state due to refusing diagnostic tests has a much higher chance of ending in death.
    Whilst some apprehension is understandable writing articles with very few statistics of merit and a lack of research into the true reasons for the use of these tests as a tool to treat people is a very dangerous thing to do.
    There is a government paper regarding radiation protection of patients which is available online it is the Ionising radiation (medical exposures) regulations of 2000. http://www.opsi.gov.uk/si/si2000/20001059.htm
    If you have any worries about diagnostic tests using radiation please seek advise from a qualified medical professional.
    Please please bear in mind the approach of not having a scan may seem sensible to those worried about radiation dose but ultimately burying your head in the sand whilst a illness eats away at you will may well have a devastating outcome.
    Scepticism is good and a natural however don’t let it become paranoia which is not healthy.

  2. 2 jonesxxx
    February 24, 2010 at 5:38 pm

    Thanks for the feedback. All useful stuff.

    However, I take issue with “very few statistics of merit and a lack of research..”

    The statistics I quoted were from such reputable sources as the University of California San Francisco, BUPA and The Lancet. Second hand admitedly, a bit like your comments.

    Further, this was not an article claiming to have performed the analysis which is why it contained no research. It was an article drawing people’s attention to some worrying information elsewhere.

    I note that the same criticism could be made of your response: It contained few stats and lacked research.

    You may be studying radiography but I am a experienced risk professional and when I read that 700 of the 124,000 new cases of cancer in the UK each year could be due to medical X-rays I am concerned. As you should be. Consider the legal implications if nothing else. Nobody has ever warned me of adverse effects when I have had X-Rays. Can I sue?

    The tone of your response strikes to the root of the problem. You are part of the establishment and see no reason to upset the silly little people who may worry about the big machines. If some of them get cancer it is all for the common good.

    I once went for a chest X-ray and as I sat on the table waiting for the “expert” to be ready she set the thing off accidentally. She seemed quite concerned but I have no idea whether I was blasted in the face by this thing or whether she was particularly nervous about using too much film.

    Personally I I favour a more libertarian approach and would prefer to be told the opinion and make my own decision.

  3. February 24, 2010 at 6:42 pm

    What exactly is your basis for wanting to sue? this obviously depends op-on the law of the country in which you reside, however can you prove that the X-ray has Caused you any harm? I imagine you would have a hard job proving diagnostic imaging is the cause of injury or disease, Do you travel by air? if you do a single flight from London to new York will expose you to more radiation than a standard X-ray. so I would imagine being able to identify medical radiation as a cause of disease to be very problematic and not likely to be successful.
    With regards to the inadvertent exposure when you went for a chest X-ray, you are within your rights and I would also want to have the person at fault dealt with, whilst it is a small done it is not a good thing to happen and the person who did this can have fitness to practice proceedings brought against them, if you can remember where and when this happened contact PALS at the relevant hospital. They will happily deal with this on your behalf.
    The issue is informed consent which is different from blinding people with science now some people may be fully aware or at least be able to understand the concept of what is happening to them others think they will become radioactive and some are very confused. What you deem to be a appropriate level of detain in terms of a person explaining a procedure to you should always be detailed enough if you feel worried or anxious, ask they should be happy to answer your questions and you are within your rights to refuse any treatment you wish.

  4. 4 jonesxxx
    February 25, 2010 at 7:49 pm

    You ask why anyone would want to sue. I guess the answer might be that their partner had died of cancer.

    You go on to say that you would have a hard job proving it. True, but this is provides safety for radiologists form prosecution not the general public from X-Rays. Not a very comforting defence to hear from a radiologist.

    Yes, I know air travel exposes you to higher levels of radiation as does living in Cornwall or Devon or wherever the granite is.

    I don’t think I’d get very far trying to complain about the X-Ray I had. Too long ago.

    I agree that the issue is informed consent and that this is different from blinding people with science. So far nobody has ever informed me or asked my consent when I have been exposed to artificial X-rays.

    Maybe that is the answer: Give people a card with a lot of babble on it before they get X-Rayed.

    With regards to X-Rays at airports I’ve since heard that this uses “backscatter” radiation which, I am informed, is far much less harmful. Even so, I resent having some apparatchik at an airport tell me that he has been told by his boss that someone else has determined that the machine is safe without any public debate. Then telling me that if I want to travel I must be subjected to their machine.

    Also, I’d come back to the 700 cases of cancer a year the UK.

    The Huffington posts reports that the allegation of deaths due to the recent Toyota pedal failure is 30 since year 2000. This is probably exaggerated but it has caused extended global media coverage.

    It makes me wonder if all these X-Ray machines were made by a large consumer brand and the cases for the cause of cancer were provable. What then?

  5. 5 jonesxxx
    February 25, 2010 at 10:51 pm

    The point you make that a single flight from London to new York will expose you to more radiation than a standard X-ray is good and lays into your comment that we need to inform people in a way that they can understand.


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