Sunday, December 20, 2015

Radiation Doses- What to Worry about and What to Shrug Off when we have CLL (chronic lymphocytic leukemia)

No amount of radiation is good for us. Ionizing radiation damages DNA and increases cancer risk. No question about it. 

So avoid x-rays unless they are truly needed. Even more so for CT scans, that are rarely indicated for CLL under most normal circumstances. 

We have reviewed our increased cancer risk in prior posts when we have multiple CT scans. And Wayne Wells has written this extensive review for the CLL Society on our website. Here is a link to an article I wrote titled "The Risk Of Secondary Cancer Associated With > 8 CT Scans In Patients With NHL (Non Hodgkins Lymphoma)" Remember CLL is a type of NHL.

But what about the risk from a minor dental films or an x-ray of an extremity?  When should we worry?

My dentist has been bugging me for years to have some x-rays, and I finally said yes after he provided me with this sheet that compares a dental x-ray to a CT scan to Chernobyl. 

It gets complicated, but the bottom line is that what this chart is basically tells us is that if the x-ray machines are properly calibrated, and are used properly, and are functioning normally, we don't need to sweat the small stuff when it comes to getting imaging. Also with dental films, miscalibration, should it occur is less likely to be a big deal than it is with CT scans.

This chart is from my dentist. Click on it to expand it. Lots of good information so it is worth the squinting. Apologies for the small text.

One tiny blue box equal 0.5 μSV and that is roughly equivalent to the radiation exposure from eating 1/2 a banana. Pretty low risk. The sugar is probably more dangerous.

The unit SV or Sievert is a measure of the health effects of exposure to low dose radiation. The sievert represents the equivalent biological effect of the deposit of a joule of radiation energy or 1 gray or Gy in a kilogram of human tissue. μSV is 1 millionth (micro SV) of a Sievert. 

A chest x-ray is equal to 1 green box or 20 μSV. In the chart, there are 400 blue boxes in every green box. Next there are 500 blue boxes for each one orange box that is equivalent to 10 mSv or ten 1/thousandth of an SV or ten milli-SV. For reference 1 mSv is the average accumulated background radiation dose to an individual for 1 year, exclusive of radon, in the United States. 1 mSv is the dose produced by exposure to 1 milligray (mG) of radiation. 5000 - 8000 mG is exposure dose that kills about half of us, known as the LD50 though the damage is dependent on many factors including duration of exposure.

100 orange boxes equals one yellow box of 1 SV.  Remember that 5-8 SV  is a likely fatal dose. Ten minutes exposure next to the Chernobyl core after meltdown resulted in 50 SV, 6-10 times the usual killing dose.

Life is full of risks, but a dental x-ray is not one to worry about.

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Blogger Judy Cleri said...

Great information. Thanks Dr. K.

December 21, 2015 at 7:35 AM  
Blogger Lis Wright said...

Thanks for this. As I often travel internationally, I will now be requesting a pat down. Also, I have read that SEATAC has x-ray machines that are not up to the higher standards of other major airports.

December 22, 2015 at 1:14 PM  

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