Are Our X-Rays Giving You Cancer?
NO, they are not! While there really isn’t much risk at all associated with the x-rays you’ll receive here at the office, it is very common for people to be hesitant about getting them taken even once, and more so for follow-up x-rays. I’ll admit I was hesitant before as well. So where does that fear or radiophobia come from?
The graph above shows the expected health risk associated with the dose of radiation. The straight, or linear line that starts right at zero and is angled upward is from the “linear no threshold effects theory” (LNT) which its origins date back to the early 1900’s. It was observed that high levels of radiation would cause mutation or cancers. It was theorized that the dose had a direct relation to the cancer risk. Which they did have sufficient evidence to back this up but only at the high levels of exposure, but there was little evidence to support that low levels or radiation had any harmful side effects.
The early studies were based on relatively high levels of radiation that made it hard to establish the safety of low level of radiation, and many scientists at that time believed that there may be a tolerance level, and that low doses of radiation may not be harmful. A study in 1955 on mice exposed to low dose of radiation suggest that they may outlive control animals.[11] The interest in the effect of radiation intensified after the dropping of atomic bombs on Hiroshima and Nagasaki, and studies were conducted on the survivors. Although compelling evidence on the effect of low dosage of radiation was hard to come by, by the late 1940s, the idea of LNT became more popular due to its mathematical simplicity.
The other line on the graph that dips below the line for a dosage from 0-10 REM, which suggests a positive health benefit or decreased rate of cancer, is a reflection of the radiation hormesis theory. This theory is based on much more current evidence and studies but is considered controversial because it goes against what has been believed to be true for many years.
Radiation hormesis is the hypothesis that low doses of ionizing radiation (within the region of and just above natural background levels) are beneficial, stimulating the activation of repair mechanisms that protect against disease, that are not activated in absence of ionizing radiation. The reserve repair mechanisms are hypothesized to be sufficiently effective when stimulated as to not only cancel the detrimental effects of ionizing radiation but also inhibit disease not related to radiation exposure (see hormesis).[1][2][3][4] This counter-intuitive hypothesis has captured the attention of scientists and public alike in recent years.[5]
So where do X-Rays in our office fall on this graph? A typical lumbar set of radiographs, that’s 2 pictures taken from front to back and from the side will give the patient at dose of 2.2 mSv which is about .22 REM (I use the lumbar as example because this will give the greatest dose in any of the x-rays we’ll take). Some other numbers for comparison:Natural Background3.1 mSv/year10Domestic Pilots2.2 mSv/year11Average US Exposure6.2 mSv/year107 Hour Airline Flight0.02 mSv12Chest x-ray (2 views)0.10 mSvChest CT7.0 mSv
There essentially is no more risk with getting x-rays at our office than you’d have with taking a domestic flight. With most of our health decisions, there’s always the question of risk vs. reward. The knowledge of the condition of your spine, and the ability to then work towards improving it, will always outweigh the almost non-existent risk of cancer from plain radiographs.
-Dr. Mark
References:
LNT Theory – https://en.wikipedia.org/wiki/Linear_no-threshold_model#Controversy
Radiation Hormesis – https://en.wikipedia.org/wiki/Radiation_hormesis
Radiation Dose converter – https://www.calculator.org/properties/radioactive_dose_equivalent.html
X-Ray Risk – http://www.xrayrisk.com/calculator/calculator-normal-studies.php