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Danger in CT scans

  1. Oct 24, 2004 #1
    I was recently reading pop sci and it revealed the following stats

    For one full ct scan

    • 1,300: Radiation dose in millirems
    • 1.5 miles: distnace you would need to bee from the Hiroshima atomic explosion to recieve an equivalent does
    • 29: radiation does in mrem from smoking pack of cegarettes
    • .08%: increase in risk of death from cancer
    • 3.75%: increase in risk of death from cancer if you have a full body CT scan annualy from age 25
    • 300: Average annual radiation dose from natural sources a year in millirems
    • 1: Average annual radiation doese in mrem from eating one or two bannas a week
    • 57 million Number of full body CT scans performed in 2003
    • $16 billion Estimated annual cost of unecessary diagonstic imagine
    • 7%: Percentage of patients infromed of the risks of their CT scans

    What are your opinions on this
  2. jcsd
  3. Oct 24, 2004 #2


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    I'm sure people do CT scans for the fun of it, when they are bored with nothing better to do. We should outlaw such recreational CT scans, especially when they are people who are obviously addicted to them and want to do them once a year from the age of... what... 25?

    Let me first apologize for what I'm about to say, but it is highly irresponsible for you to spew such meaningless statistics without even mentioning the possiblity of the benefits of such an procedure might outweigh the risk. There are people with serious illness who would tremendously benefit for such diagnostic procedure, the same way a memogram, dental x-ray, etc. would be even with the associated risk. People seem to forget that they accepted larger risks than these each day they get onto an expressway going to work.

  4. Oct 24, 2004 #3
    I agree--- take nothing away of the importance of CT scans--- the facts i got were from an article from popsci that just gave the stats as i have mentioned... I do wonder about the number of ct scans that are done on doctor recomindation that could be avoided--- 16 billion dollars in scans were not needed
  5. Oct 24, 2004 #4


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    I question the number that is cited, and I will also question who decided that these scans were "not needed". This is especially true when insurance companies are scrutinizing everything a doctor is requesting. That many unneeded order on an expensive diagnostics passing through tight-wads insurance companies? I don't think so...

  6. Oct 24, 2004 #5


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    Well, my first and overwhelming reaction is "So what?"
  7. Oct 25, 2004 #6


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    Me too. The reason, as already stated, these stats are utterly devoid of context.
  8. Oct 25, 2004 #7
    Finally, from a health risk standpoint, an acute dose of 1300 millirem is negligible. Radiation workers (those who work regularly with radioactive materials) are allowed to get up to 5000 rem per year.
  9. Oct 25, 2004 #8
    As i mentioned I got these stats directly from Popular Science page 48 November issue.

    The sources are
    American College of Radiology, David J Brenner/Columbia University Medical Center, U.S> Food and Druge Adminstation, David C Levin/Thomas Jefferson University Hospital, Natinal instuutes of Health, Nuclear Energy Institute, Yale University of Medience

    It is hard to be out of context when the whole article was just the stats...

    The thing that gets me is the 16 billion dollars and 7 percent.... people should know when they need a CT scan and when other options are avalibable. I have had to get

    CT Scan

    and now am supose to get a bone scan

    for a groin injury... the doctors haven't done anything in pinpointing what has been the source of the injury that I have had for over a year...

    a .08% increase in risk of death by cancer is ennough to make me look at other options first... plus the cost of the scans are ridicolus
  10. Oct 25, 2004 #9
    I am not sure if it makes a difference if you get 1300 within an hour vs 5000 rem per year... but if it doesn't then 5,000 mrem should be taken a lot more seriously with the publication of data like this
  11. Oct 25, 2004 #10
    First, my sincere apologies. Radiation workers are allowed to get 5,000 millirem in one year, not 5,000 rem!!! Whew!!!

    But, that said, an acute dose of 1300 millirem or an acute dose of 5,000 millirem will have no somatic effects. For everyone's information, here is some data on acute radiation dose effects:

    There will be no noticeable health effects from acute radiation exposures until the level reaches about 35,000 to 50,000 millirem. At that level there will be temporary detectable blood changes

    Around 100,000 millirem, some people will exhibit the symptoms of radiation sickness: fatigue, nausea, vomiting. They will recover in a few days.

    About 50% of people exposed to an acute dose of 450,000 millirem will die without medical treatment. With medical treatment, the percentage of deaths will go down, but some people will still die at this level of exposure.

    Essentially 100% of those people exposed to 1,000,000 millirem or more will die, even with medical attention.

    The main effect of chronic exposure to low levels of radiation is an increase in the chance of cancer. But, the data reported above (.08% increase in the chance of cancer after exposure to 1300 millirem) is misleading. I believe this comes from a 1990 report by the National Research Council's Committee on the Biological Effects of Ionizing Radiation (so it's not new data). This is actually a population risk not an individual risk. The proper interpretation of this is that exposing a population of 10,000 people to an acute dose of 1,000 millirem could result in as many as 8 cancer deaths in excess of what would be the normal number. It doesn't mean that your personal risk of developing cancer has increased by .08%. The normal number of people expected to die of cancer in a group of 10,000 is 2,000.
    Last edited: Oct 25, 2004
  12. Oct 25, 2004 #11
    thank you for your information--- I was not specifically trying to support the article as much as see some discussiona bout the figures your response was very helpful
  13. Oct 25, 2004 #12
    You're welcome. I figured you were looking for some context for that information.
  14. Oct 25, 2004 #13


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    Let's see. Google finds

    duke CAT dose calculator

    With the default mass of 70kg, I get

    402 millirem for abdominal CT
    544 for chest CT

    That's a total of 946 mrem, about 1 rem. There's no entry for "whole body CT", but the sum of chest + abdomen is reasonably close to your figure, though your figure is slightly high.

    The EPA currently estimates

    Epa rad effects

    For a CAT scan, you get the dose in one lump, but if we use these figures as an estimate, that's about 1 chance in 2000 of dying of cancer as a result of the exposure. This is a small fraction of your chance of getting cancer "naturally". The EPA doesn't mention this, but as I recall, it will take 20-40 years after exposure for the cancer to develop. If you are old enough when you get the exposure, you may not live that long anyway :frown:. Somewher or other, I saw age adjusted charts, but I don't recall where or by whom, and I doubt that they are current in any event.

    Sidenote & political comment: It's a bit hard to tell who to believe. I've seen far to many "pro-radiation" people in the health science fields for my comfort level - people who believe ionizing radiation is good for you. (It's very likely that they are having their research funded by pro-nuclear interests, too.).

    One chance in 2000 of death is nothing to sneeze at. If you are sick (and especially if you are already old and sick), you have to factor in the benefits. If there is a 1% chance the CAT scan will find something serious that would otherwise be missed, this would far outweight the .05 percent chance that it kills you. It's hard for me to asses the specifics of "how good" CAT scans are.
  15. Oct 25, 2004 #14

    There are three major competing theories with regards to the effects of radiation exposure. The one that current exposure and radioactive material cleanup regulations are based on is the "Linear, No Threshold" theory. This theory assumes that any amount of radiation exposure, no matter how small, is harmful and that the consequences of exposure increase linearly from zero.

    The second theory is basically the same except that it assumes there is a threshold exposure level, below which radiation has no adverse effects. There is some evidence of this, but it's still not widely accepted.

    Finally, and this goes to what prevect was saying, there is the "Radiation Hormesis" theory. This theory says that small doses of radiation are actually beneficial. They are supposed to "tune up" your immune system. Believe it or not, there is some evidence to support this, but it is in a distant third place among most health physicists. There was however, an article in a recent Science magazine about the Radiation Hormesis theory.

    There is active research going on concerning all three theories.
  16. Oct 26, 2004 #15


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    Well, holy cow. Do I have a LOT to say about this! Unfortunately, there is an election going on that I am very involved and active in so, most of what I'd like to say will have to wait.

    I have been an x-ray technologist for over 30 years. I have done general radiography, mammograms (NOT MEMOrams, Zapper Z!! :rofl: :rofl: That was GREAT!! I'm picturing us trying to compress a stack of MEMO's with the mammogram machine... :rofl: :rofl: :rofl: Sorry. I digress... :biggrin: ) and I have done CT scans for almost 25 of those years.

    CT scans ARE one of the highest dose exams you can have. But there are a number of factors to consider. The average 'technique' used on an abdominal helical CT is 400MA at .5 sec (or 200 MAS) at 120 KV. Generally speaking, the higher the KV, the more penetrating the beam. Also, the higher the MAS, the more photons you HAVE penetrating the part you are imaging. So with 200 MAS at 120 KV you have a moderate amount of photons going through the body at maximum penetration (120-130KV is typically the highest we use in diagnotic imaging). This combination keeps the biological damage to cells/tissues considerably lower than using LOW KV and HIGH MAS.

    Now, consider the amount of radiation received to JUST the breast area (including the sternum - which is a major producer of bone marrow which makes your blood) during a routine screening mammogram. According to pervect's link to Duke's dose calculator, each image delivers an average dose of 143mr. Multiply that by 4 (two images of each breast) and you have considerably more dose than your average abdominal CT. What makes the dose so bad, is that the average kilovoltage setting for mammography is 25 KV. This is a very low-penetration photon going through the breast and doing MUCH damage along the way to its exit - IF it exits. A lot never make it out of the breast. To compound the problem, you need a VERY high MAS - LOTS of photons - to produce the detailed images you need in mammography. I've often wondered if mammogram dosage is the real reason why breast cancer is on the rise. I've discussed this with numerous radiologists and many of them have (off the record of course) have actually admitted to wondering that, too. When I asked them why no one is doing any kind of study on this, they indicated that because mammography is such a GIANT money-maker, there is just no incentive to find a different way of imaging breasts. I personally think that MR is the way of the future for breast imaging, but at this time, it is not a technological or financial possibility.

    So, while the concern about the dose in CT scans is definately warrented, (and please know that your CT technologists are HIGHLY trained professionals and ARE using the lowest dose possible to produce the best diagnostic image for your patricular exam - we are required to produce evidence of continuing education to maintain licensure), I feel there should be a WHOLE LOT more concern about mammogram dosage.

    Gotta go to the dentist, now. :eek: See ya!
  17. Oct 26, 2004 #16
    Ok, so I don't think most those numbers are that bad, but I do have a problem with the 7% of patients being informed of these side effects. The benefits outweigh the risk in most cases as stated earlier, but wouldn't you want to know the risks before going through one of these procedures? Or equivalence?
  18. Oct 26, 2004 #17


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    Well, before you decide you have a problem, you should make sure there's enough risk to warrant informing patients.
    Last edited: Oct 26, 2004
  19. Oct 26, 2004 #18

    If you bought a new car, but that car had a 7% risk of catching on fire, wouldn't you want to know? The car company may determine it not enough risk to tell the customer, and when it does happen, they can pay whatever suing fee or possible medical and mechanical bills, but I would at least want to know that it could happen to my brand new car. And the CT scan is on our body, it's not like we can bring it in for a tune up and jsut flat out replace bad parts....maybe in the future when we have a cure for cancer we can just say, oh well and give the cure, but today where cancer is a huge threat to life when you get it, that's kind of the sort of thing I would like to know.
  20. Oct 26, 2004 #19


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    Yes, I would.

    Fortunately, you don't have a 7% risk of catching fire in a CT scan.
  21. Oct 26, 2004 #20
    But you do have a 7% increase of chance in developing cancer later in life, and isn't that just like a fire in our cells(abstractly put)?
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