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Editorials, evidence based medicine

Why the radiation of a chest or dental x-ray isn’t the same as 2 days in Denver

My kids were at the dentist this weekend for their routine cleaning and check ups (yes, Saturday hours!) when the hygienist mentioned x-rays. I smiled and mentioned I’d rather discuss the need with the dentist after his exam. This isn’t a dental x-ray thing, this is what I do for every test that involves ionizing radiation.

My son, Oliver, has had more radiation than most people will have. Ever. In fact, as he was extremely premature he had more radiation than most people will have in a lifetime before he was supposed to be born. In addition to the 30 or so x-rays he had over 9 1/2 weeks in the neonatal intensive care unit (NICU) he had a challenging procedure done under fluoroscopy to pop open his pulmonary valve when he weighed 3 lbs (when he should have still been a fetus). I read that the estimated radiation dose from that specific procedure is calculated at about 1,000 chest x-rays. It’s an older study and so I hope the calculations don’t apply to today’s imagining, but I admit I felt sick.

Oliver continued to have more chest x-rays long after he left the hospital that first time, probably another 25 or so over the next 5-6 years in addition to another fluoroscopic procedure when he was two years old, although this one was slightly less challenging so I’m hoping for a cumulative dose of maybe 200 chest x-rays. Oliver is also going to need at least one more fluoroscopic cardiac procedure and at some point our no-pneumonia-requiring-hospitalization-for-3-years streak will break and he might need another chest x-ray or two (because Oliver also has the gift of damaged lungs).

Radiation risk, from a cancer perspective, is higher the younger the age of exposure, but I don’t just think about that for Oliver and his twin, Victor. I think about it for my patients as well. I carefully weigh the risk and benefits of radiation because there is no “safe” lower dose. While it is true that the lifetime risk of cancer from medical x-rays is small, it is not zero. The biggest risk (looking at more common procedures) comes from a CT scan of the abdomen or pelvis. When performed at the age of 20 about 1 additional person in a 1,000 will get cancer from this test, so quite small compared to the chance of getting cancer in general (about 1 in 5 people will get cancer in their lifetime), however, enough CT scans are done that the procedure raises the population’s risk and if you are that “one” then it’s 100% for you. If you had a new pain and a fever and the CT scan diagnosed an abscess leading to medical care that saved your life then that 1 in 1,000 risk was worth it, however, if you have chronic pelvic pain and the chance that anything causing your pain will be identified by a CT of your pelvis is less than 1 in 1,000 then that risk isn’t favorable.

What about the whole background radiation thing? Many people bring this up as evidence that radiation in most clinical doses is safe, but I ague it isn’t a fair comparison. The chart below (from the FDA) shows radiation exposure with a variety of procedures and how that compares to the background radiation of life:

Screen shot 2013-09-22 at 12.28.14 AM

A CT of the abdomen is the radiation dose for 2.7 years. If I’m meant to live 90 years or so I can absorb the radiation of a few CT scans, right? While equating radiation dose from a procedure into relatable term helps from an understanding standpoint, in my opinion it doesn’t imply safety because your cells taking in 8 mSV of radiation over 2.7 years is a lot different from your cells absorbing that same dose over 20 seconds. Let’s use the same analogy with calories. In 2.7 years you will consume roughly 197,000 calories. What do you think would happen to your body if you were forced to consume those calories in 20 seconds or if you were forced to consume 2.4 days worth of food in less than a second.


Instead of abstract terms, such as radiation doses living in Denver versus San Francisco, what every patient needs to know is specifically how this x-ray will enhance their medical care and what are the potential risks. Every test has a risk-benefit ratio especially when radiation is involved. While a recent study raises the possibility of a link between thyroid cancer and dental x-rays taken before 1970 (interestingly not for people who were exposed as children or adolescents), the study really asks more questions than it answers.

In my opinion it is a good idea to follow the FDA recommendations, which indicate that providers should do the following:

  • Discuss the rationale for the examination with the patient and/or parent to ensure a clear understanding of benefits and risks
  • Justify x-ray imaging exams (my kids are going to need braces and I specifically chose a orthodontist
    Cone-beam CT

    Cone-beam CT

    known for limiting x-rays who doesn’t use dental cone-beam computed tomography, in his words, “Yeah, they’re cool and you can charge a lot, but in my opinion no kid ends up with better looking teeth.” The idea of using a CT scan for braces just floors me).

  • Determine if the examination is needed to answer a clinical question
  • Consider alternate exams that use less or no radiation exposure
  • Review the patient’s medical imaging history to avoid duplicate exams

I spoke with the dentist. He did a thorough exam and it turns out that Oliver is still a pretty good brusher and flosser. Oliver also gets fluoride, does not drink soda, eats very healthy for a 10-year-old, has never had a cavity, and goes to the dentist regularly. “What will the x-rays add?” I asked

“They can pick up carries between the teeth that I can’t see,” was the answer.

And so Oliver’s dentist and I agreed that as his teeth and gums look great and he is in the lowest risk category with a history of far more radiation exposure than most children that we would just hold off on the routine x-rays for now and re-asses at his next visit in 6 months. Oliver’s twin brother, Victor, is a less dedicated brusher and flosser, eats way more candy, and has already had a cavity and while he has had more radiation than most, he is not in Oliver’s league. Victor’s risk-benefit ratio from a screening dental x-rays is different than Oliver’s and I have him on the dentist’s recommended schedule.

The FDA’s recommendations are sound. Don’t have any x-ray (or any test for that matter) until you have reviewed the benefits as well as the risks and that you and your provider are both assured it’s truly necessary. For the vast majority of children the risk-benefit ratio for dental x-rays will be largely in favor of imaging on the recommended schedule, but don’t try to sway me based on how the radiation of a chest or dental x-ray compares with a flight or living in Denver because it’s just not the same thing.

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10 thoughts on “Why the radiation of a chest or dental x-ray isn’t the same as 2 days in Denver

  1. Two thoughts that add my perspective:
    1. Remember that there was a fashion for treating asthma by irradiating the thymus of affected kids in the 1950′s. It was halted after a large proportion developed thyroid cancer.
    2. As a med student in the 1970′s I remember being shown a guy who had too much radiation to his groins: both were pus filled holes with the femoral artery making waves in the bottom. The arrangement was that when the artery eventually eroded through someone would cover the hole to prevent a mess on the ceiling but do nothing else.

    In other words, radiation is nasty stuff and you want to be sure you can justify the test. I even worry about the protocols for following pulmonary nodules to ensure they aren’t growing and thus less likely to be cancers. Such protocols might involve three monthly CT scans of the chest for a couple of years (which equals 400 x 8 = 3,200 CXRs), and they are designed simply to reduce the risk of litigation against the radiologist who needs to cover his arse. However, they are standard of care so that’s what we do….

    Posted by lancelotgobbo | September 22, 2013, 5:46 pm
  2. Is a chest X-ray really equivalent to a dental periapical X-ray dosage, even digital?

    Posted by Anthony Kilcoyne | September 23, 2013, 1:03 am
  3. I’m torn on how to respond here. On one hand, as a dentist who routinely takes radiographs and sees their benefits… and as someone who routinely gets bombarded by Dr Oz watching idiots who have zero idea what they’re talking about… my first hand is to say “oh gee… here we go again”. On the other hand… I sincerely respect your education on the matter and your willingness to discuss the issue and be aware of what’s in your child’s best interest. You’re obviously very well educated on the subject and I can’t tell you how incredibly refreshing that is. Kudos x 1000!!

    A few things to remember. 1) as a doctor… it’s my right to refuse to treat if you refuse to allow me to do a proper diagnosis. For someone I’ve never seen… a proper diagnosis includes DIAGNOSTIC (that is current and readable) radiographs… always… zero discussion about it. 2) as a doctor… my job is also to do no harm… or more accurately to limit my administration of harm to make sure that it does more good than harm. So in that vein I can respect your desire to make sure your child is getting the best care possible and I have often agreed with patients to take radiographs only every 2-3 years. These are also patients I know very well and have established a history with and, who like the authors child, show minimal risk. 3) Everyone please take heed of how educated this person is on the subject. I’m much much more inclined to agree with or compromise with someone who knows what they’re talking about… vs someone who watched Dr Oz and wants to use this encounter as an instance to proclaim their individuality and freedom from the medical world. Those are generally people I refuse to care for and ask to go elsewhere. 4) Understand that my (and really any dentist’s) fees are based on the whole package of services provided per unit time. Please don’t be offended that if we agree to only take radiographs every 2-3 years or so that we must also agree to raise the fee for other services in order to keep that fee per unit time number in check with what it costs me to provide the service. I agree it’s unfortunate that insurance companies have forced us to think like that… but I can’t structure my entire practice around a few patient’s specific needs (and I sincerely mean that with all due respect!!!). A more fair system would be that you pay a fee per time, much like a lawyer, regardless of what services we do or don’t do. Unfortunately we’re not there yet. 5) Everyone please understand that this patient’s circumstances are very rare, and very specific, and research and data have established that for a routine patient who has not had enormous exposure to ionizing radiation… that the dose of radiation from modern digital radiographs is exceptionally minimal and the risk is exponentially minimal compared to the benefit they provide. I have seen case after case of 5, 4 or even 3 year old patients that have dental decay significant enough it warrants hospitalization or in some cases removal of all their teeth. I have also seen many cases of instances where a dentist performed treatment that was completely inappropriate and ineffective because they eyeballed it and didn’t have proper radiographic information. 6) as the poster above alludes to… many of our medical diagnostic tests are unfortunately necessary to protect ourselves against ridiculous litigation. We’re in a difficult position. Many people think “you can’t take x-rays… but if you miss anything it’s your fault and I’ll sue you”. It’s an unfortunate reality that we must deal with. I’d advise anyone reading to take an active role in modern tort reform. Also please don’t be offended if I ask you to sign a waiver of liability acknowledging your decision and asking you to take responsibility for your decision instead of being able to later throw that responsibility on my shoulders should something be less than ideal.

    There’s no one size fits all solution… there are however guidelines. If you feel your child (or yourself) fall outside those guidelines then a discussion is warranted. But it’s also very important to understand that those guidelines exist for a reason… and that very few individuals fall outside of them. Bottom line… find a healthcare practitioner you trust and feel comfortable with.

    Posted by Eric Boyd | September 23, 2013, 6:05 pm
  4. I’ve read through the comments and they leave me wondering: Is the standard of dental care different for children than adults? I’m in my late 40′s and have had exceptionally cavity-free teeth. While my dentist took x-rays when I first started seeing him, once he established that baseline and had examined me a few times he only takes them about every two years. He also doesn’t charge me any differently than other patients. Is this unusual? Is he x-raying me less because I am older or because I have a history of no cavities?

    My biggest concern with radiation exposure is that I have a medical condition (hypothyroidism) that can be made worse with lots of radiation to my thyroid. Whenever I have diagnostic x-rays (included mammograms), I make sure I’m wearing a lead thyroid shield. (As an aside, can’t we come up with something better than the current mammogram procedure for breast cancer screening?! I admit that I skipped my mammogram this year because I just didn’t want to deal with the pain and I’m low risk with no family history. I know…shame on me…but, damn, it sucks!)

    Because of my desire not to irradiate myself (and specifically my thyroid) any more than necessary, I refuse to walk through the imaging machines at the airport. It seems to really piss off the agents at times and they will try to argue with me, but I just keep repeating that I’m following doctor’s orders (OK, a bit of a lie since my doc never said specifically to not walk through an imaging machine) and stand my ground. Am I being an asshole? Do I really have no reason to worry about the radiation from the scatter wave imaging machines at the US airports?

    Posted by Linda | September 25, 2013, 6:21 am
  5. Reblogged this on AntiRadiation.

    Posted by andiradi | September 26, 2013, 2:47 am
  6. I think you are doing the right thing Linda and I should do the same. I have had cancer and have a kidney transplant so have had multiple xrays etc. I visited the US recently and went through the full body scanner without a thought. A month after coming home I thought S*** – I should have refused! I am a frequent traveller so will avoid all scans in the future.

    Posted by Catherine Voutier (@CathVoutier) | September 26, 2013, 6:46 pm
  7. I think you have to distinguish about ionizing radiation to the germ cells, and to somatic cells. My 12 yr old needed a CT to the groin, and that was a major discussion, under emergency circumstances. It was the right thing to do, life saving surgery followed immediately. Single lower dose X-rays to somatic tissues later in life (mammograms): just do it. Benefit outweighs risk. I argue there are doses of radiation that are harmless, there is a limit below which the dose is completely handled by the DNA repair mechanisms active in our cells. There are folks living in parts of Iran, I believe, that have naturally high doses of radium (something like 100x background), and have for millennia. Their DNA repair machinery apparently deal with this level without increased cancer risks. So I believe there is a threshold below which there is not a worry. But it is important o realize that clinical use of ionizing radiation is a risk/ reward decision, and to make informed choices.

    Posted by Pkin | September 30, 2013, 8:21 pm
  8. As a breast surgeon, I was hoping you would touch on the effective dose one receives for a mammogram, since this is a screening tool that every woman over 40 should have every year. I often give lectures to groups and one topic that comes up is the risk of radiation exposure from mammograms. I’ve estimated the risk to be very small for each image taken, but when it’s a tool used on an annual basis, some patients have concerns. IMO, the potential benefit of early detection definitely trumps the risk, as we have seen at least a 30% reduction in mortality from breast cancer, attributed to early detection. But I do agree that we probably order way too many diagnostic tests that may not really enhance the medical decision-making in some cases. For example, CT scan of the abdomen/pelvis for suspected acute appy, especially in children. Old-school surgeons still say today that this is really a clinical diagnosis based on physical exam findings, rather than what you see on a screen.

    I enjoyed your article, as it gave me more insight into the topic of radiation exposure for our patients.

    Posted by Christopher Menendez | October 24, 2013, 7:05 am


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