Medical Imaging: How Safe Is It?

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At this stage of our Boomer lives, getting some scan or another is pretty routine but how safe is Medical Imaging? I dig into the patient handout from Australia’s radiation protection agency and research from Melbourne University. In short, take care.

Main Points

  • Aussies get 300% more radiation from Medical Imaging than any other source;
  • Medical Imaging uses different types of radiation; some are more harmful than others;
  • Some forms of radiation are cumulative & significantly increase our cancer risk;
  • Not all Medical Imaging is necessary but how do you know?

If you’d like to skip to the many causes of cancer, including radiation and a host of others, check out our detailed, easy-to-read guide – based on research from over 400 sources: Cancer: Make Your Own Luck

The Guinea Pig & the Chicken

My cardiologist suggested three CT (Computed Tomography) scans to figure out what was wrong with my heart and my neurologist suggested five MRI scans to figure out the same for my back. (I did succumb to the CT scans but not the MRIs. Embarrassingly, this wasn’t due to lower perceived risk with MRI; my first MRI was the most bizarre, claustrophobic experience that I hope I never have to repeat. In other words, I chickened out.)

Let’s look at the various types of medical imaging, courtesy of ARPANSA (Australian Radiation Protection and Nuclear Safety Agency). I’ve included the agency’s ranking and range for the lifetime risk of a fatal cancer in brackets. The full Patient Handout is here.   

Types of Medical Imaging and Risk

  • X-rays are a form of radiant energy that penetrates the body to provide internal images. (Very Low Risk: 1 in 10,000 to 1 in 100,000)
  • Computed Tomography (CT) scans are X-rays which take multiple images rapidly around a patient to provide images of soft tissue, bone and blood vessels at different depths. (Low Risk: 1 in 1,000 to 1 in 10,000)
  • Mammography uses X-rays to image the breasts, mainly to screen for early signs of
    breast cancer. (Very Low Risk: 1 in 10,000 to 1 in 100,000)
  • In Nuclear Medicine, the patient swallows or is injected with a radioactive material that emits radiation similar to X-rays and builds a picture of what is happening inside. Main types are PET (Positron Emission Tomography) and Bone Scans. (Low Risk: 1 in 1,000 to 1 in 10,000)
  • Fluoroscopy shows a continuous ‘X-ray movie’ on a monitor while a body part or dye is moving through the body. (Low Risk: 1 in 1,000 to 1 in 10,000)
  • Bone Density Testing (also called or DEXA (Dual-Energy X-ray Absorptiometry) or BMD (Bone Mineral Density)) uses low X-ray doses to measure bone density. (Negligible Risk: 1 in 1,000,000)
  • Magnetic Resonance Imaging (MRI) uses magnetic fields and radio-frequency waves to penetrate the body and produce internal images. (Nil Risk)
  • Ultrasound (or diagnostic sonography or ultrasonography) uses high frequency sound waves to see internal structures like tendons, muscles, joints, vessels and internal organs. Often used for pregnant women. (Nil Risk).

I was a bit surprised that ‘Low Risk’ (for developing a fatal cancer later on) was as high as 1 in 1,000 , especially as radiation damage accumulates (see more below). In other words, after several scans, the risk could be much higher than 1 in 1,000.

In its Patient Handout ARPANSA also explains what the various levels of risk equate to in terms of likelihood.

  • 1 in 1,000 = Risk of Drowning
  • 1 in 10,000 = Risk of Bicycle Accident
  • 1 in 100,000 = Risk of Lightning Strike

ARPANSA gives the useful exposure comparison graphic (below) which shows that radiation from medical imaging is by far the major source of radiation for the average Australian.


What Are the Risks?

For MRI and Ultrasound, the risk is nil because sound or magnetic waves are used, not electromagnetic radiation. In other words, they’re not on this spectrum.

The others, which are based on X-rays, are called ionizing radiation, located at the high frequency end of the electromagnetic spectrum (see below). At the low end are radio waves (which are not the same as the sound waves used in ultra-sound).

The problem is that damage from ionizing radiation is cumulative (each dose adds to the last) and, these days, if one scan finds something inconclusive, another may be recommended straight away.  

Source: Centres For DiseaseControl

If it’s a CT scan like an Angiogram (for the heart) like I had, the dose each time is 10 millisieverts or 10 times the recommended annual exposure to radiation (that’s extra to the unavoidable daily-life exposure) which is 1 millisievert per annum.

A one-off study of its kind was conducted by the university of Melbourne about 10 years ago. Based on 11 million Australian Medicare records, it concluded that one CT scan increased the cancer risk by 24% and the next by a further 16%. In my case I had 3 CT scans of different types in as many months, totally 18 mSv or 18 times the recommended annual exposure. One study estimated that at least 2% of all future cancers in the USA—almost 30,000 cases and 15,000 deaths per year—would stem from CT scans alone, so this procedure is not exactly harm-free.

That said, the body can repair some cell damage resulting from ionising radiation, so long as it has enough time to do so. Yet, if you have repeat exposure to radiation in a short period (like I did), any damage done will take longer to repair, if it can repair at all. Also, in children and older people (like us boomers) the sensitivity to radiation is higher. For children, it’s because their cell division is faster (due to growth) and for us, it’s because our repair mechanism is less precise.

Is All Medical Imaging Necessary?

You may be saying, ‘Well, my doctor ordered this scan, so I must need it, right?’ That is a comforting thought but, it appears it isn’t always so.

The FDA (Food and Drug Administration) in the USA estimates that up to 50% of CT scans are unnecessary. PubMed tells us that medical radiation exposure in the USA increased 600% in just 3 decades. In Australia, we have the second highest number of CT scanners per capita in the world (second to Japan). Also, Down Under, CT scans (and X-rays, MRIs, Ultrasounds and PET scans, too) are fully or partly covered by Medicare, so cost is no longer the barrier it once was.  

All things considered, maybe, all medical imaging scans are not necessary and not safe. The risk of cancer is real, it seems.

Get all the details about medical imaging, the real causes of cancer and how you can cut your chances of a cancer diagnosis – in our ebook Cancer: Make Your Own Luck. Click below to check out what’s inside.

Cancer: Make Your Own Luck


Discover how Aussie boomers can take control & cut the risk

Kim Brebach

Kim Brebach

Hi, I’m Kim Brebach, boomer, information researcher, technical writer and Joiner of Dots at M&M. In my spare time, I review wines and love to cook.

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