DEXA Tests and Radiation – Need You Be Worried?
Should you be concerned about the radiation from DEXA machines that screen for osteoporosis? It does sound worrisome, especially when you consider that the “D” in DEXA stands for “dual” xrays.
Do they pose double the risk of the already risky x ray practice? Or are the hazards negligible? Let’s dig into this mysterious invisible technology to see if you should be alarmed.
But before we do, let’s recap on how and why DEXA machines have become so common, and important to your health.
DEXA is now almost a household name because of the rapid growth of osteoporosis. The growth of it, called ‘epidemic’ by the Surgeon General, means more and more people are suffering fractures from minor events that wouldn’t have previously hurt. An innocent fall that you would’ve laughed off before – even sneezing or coughing has been know to break bones in those with porous bones.
The condition known as osteoporosis has reached breakneck proportions due to a variety of reasons, mostly to do with our modern lifestyle. 10 million Americans have it. But an estimated 34 million are on their way to developing it, which is even more concerning. (1)
When history looks back at the 20th it will describe an era that in lightening speed advanced our world with incredible changes such as the automobile, space travel, television and the internet.
However, future historians will also write how within the 20th century we did an about face on how we eat. We learned to speed up delivery, extend shelf life and maximize yields of our food. All these ‘advances’ increased quantity and immediate pleasure, but drastically reduced food quality and thus, our health.
20th century technology and industrial invention also automated and moved our work indoors, which required more of our brains but not so much our physical bodies.
These huge deviations definitely made our lives easier, but our bones (and overall health) are paying a price for it. The nutritional decline of our food system means your skeleton doesn’t get the minerals necessary to stay strong.
And because of the incredible leaps and bounds of modernity our physical bodies simply aren’t put to use as they were throughout history, so are bones are getting softer and more porous with every generation. And our vitamin D levels (mostly provided by the sun) so vital for bone growth, have plummeted due to the last century shift to indoor work.
DEXAS: Desperate (Bone) Measures For Desperate Times
Because we have gone so far off script in the 20th century, it’s very probable that in your lifetime you will be advised to get a DEXA test to measure your bone density.
Sadly, most will test only after they break a bone. Because an unexpected fracture is usually what alerts people to the bone loss that has been going on under their surface – for decades.
For bone health the best offense is a good defense, meaning don’t wait for a fracture to get a DEXA test. Finding out early about your bone density is a smart pre emptive measure you can take. It buys you time to make simple lifestyle adjustments to fight the very real threat of osteoporosis.
Your Health: DEXA Test Essentials
DEXA is an acronym and means ‘dual energy X-ray absorptiometry’. It is a testing machine that measures the density of your bones. The calculation is done knowing that the denser the bone, the less X-rays pass through. Usually the more dense your bone, the stronger it is, and the less likely it is to fracture.
There are two different types of DEXA machines. Central DEXAs are large full body machines that measure bone density in the centre of your skeleton, such as your spine and hips.
Peripheral DEXAs are portable much smaller machines that are used to measure bone density on your peripheries such as wrist, heel or finger.
A DEXA machine uses low-energy X-rays and sends two different sources (thus the ‘dual’ part) through the bone in question. Bone blocks some of the X-rays. The more dense your bone is, the less X-rays pass through to the detector. By Two different X-ray sources rather than one are used to double the accuracy in measuring your bone density.
The amount of X-rays that comes through the bone from each of the two X-rays is sent to a computer which calculates an average score of the density of your bone.
But just how much radiation do DEXA machines emit? Thankfully, as you can see from the chart below, very little especially when compared to numerous other types of medical imaging procedures.
|Procedure||Average Effective Dose (mSv)||Range Reported in the Literature (mSv)|
|Bone density DEXA||0.001||0.00 – 0.035|
|X-ray, arm or leg||0.001||0.0002 – 0.1|
|X-ray, panoramic dental||0.01||0.007 – 0.09|
|X-ray, chest||0.1||0.05 – 0.24|
|X-ray, abdominal||0.7||0.04 – 1.1|
|Mammogram||0.4||0.10 – 0.6|
|X-ray, lumbar spine||1.5||0.5 – 1.8|
|CT, head||2||0.9 – 4|
|CT, cardiac for calcium scoring||3||1.0 – 12|
|Nuclear imaging, bone scan||6.3||?|
|CT, spine||6||1.5 – 10|
|CT, pelvis||6||3.3 – 10|
|CT, chest||7||4.0 – 18|
|CT, abdomen||8||3.5 – 25|
|CT, colonoscopy||10||4.0 – 13.2|
|CT, angiogram||16||5.0 – 32|
|CT, whole body||variable||20 or more|
For perspective, the amount of radiation emitted that’s listed on the chart above for a DEXA (0.001) is less than what you would get from a New York to L.A. flight.
If you go back a few decades, the only place to measure the health of your bones was at a hospital using a Central full body DEXA machine . But to meet the demand for the ever increasing cases of osteoporosis, more affordable, portable machines to test bone density were invented.
Due to the wonders of technology, with DEXA machines we can now safely, quickly and painlessly spot a bone density issue far on the distant horizon – and then do something about it – before a bone fracture alerts you to the problem.
- “America’s bone health: the state of osteoporosis and low bone mass in our nation”. National Osteoporosis Foundation, 2002.
- Mettler FA, et al. “Effective Doses in Radiology and Diagnostic Nuclear Medicine: A Catalog“, Radiology (July 2008), Vol. 248, pp. 254–63.