September 24th, 2011

Comparison of Radiation Doses

from :

Typical Radiation Doses (From Various Sources)*
Watching television2 0.01 mSv/year
Air travel (roundtrip from Washington, D.C., to Los Angeles, Calif.) 3 0.05 mSv
Medical chest X-ray (one film) 0.1 mSv
Nuclear medicine thyroid scan2 0.14 mSv
Full set of dental X-rays 0.4 mSv/year
Mammogram (four views) 0.7 mSv
Average annual exposure living in the United States6 3 mSv/year
Average annual exposure from breathing radon gas5 2 mSv
Nuclear medicine lung scan1 2 mSv
Nuclear medicine bone scan1 4.2 mSv
Nuclear cardiac diagnostic test (technetium or Tc-99m) 4 10 mSv
Abdominal CT scan1 10 mSv
Various PET studies (18F FDG)1 14 mSv
Tobacco products (amount for a smoker’s lungs from 20 cigarettes a day)5 53 mSv/year
Cancer treatment (tumor receives)5 50,000 mSv

Safety of Scans

I’ve been having lots of imaging tests since I got cancer.

3 chest & abdominal CT scans, 1 pelvic CT scan, 1 bone scan, 1 PET scan, 4 Muga heart scans, 1 heart echo, 3 mammograms, 1 MRI, and numerous ultrasounds.

We can also check tumor markers by a blood test besides imaging tests to detect cancer, but my oncologist says that tumor markers are not reliable as compared with the imaging tests.

In fact, last year when I was taking the first chemo regimen, my tumor marker was stable in the normal range without showing any alarm sign, according to the oncologist.

Whenever I get some concern, or even if not, I probably need to have image testing periodically for good to make sure that cancer won’t reoccur.

Yet are those exams are safe?

So, I researched about it.

First, an ultrasound, MRI, and echo have no risk.

As I look at a comparison of image tests such as x-rays, a mammogram, and scans, which radiation is used, a radiation dose of mammogram is 7 times more than a chest x-ray, while abdominal CT scan is 100 times more.  Another surprise is that smoking is more than 500 times of the chest x-ray’s dose.  No wonder we want to ban smoking.

Then here is a radiation therapy; 500 thousand more!

Numerous sites explain that if the one time dose we are exposed to is more than 2000mSv, the soft tissue such as skin, muscles, blood vessels, fat, tendons, ligaments, or nerves may get damaged.

While I was receiving radiation therapy, my skin turned red, but several weeks after the therapy was over, my skin started pealing thickly and the affected area became oozing and burning.

4 months after, now my skin is healed, but tightness or stiffness is still there.  All new findings in my left lungs are also apparently from the affect of the radiation.

Fortunately, as it is also said that our bodies have a healing power, I expect that my injuries can be healed eventually.

So far the data of long usage of such image tests is unknown. For safety, the specialists are suggesting us to:

1.  Ask a doctor if a test is necessary or not:  discuss about the risks of taking a test and of not taking a test.

2.  Ask if alternative tests such as ultrasounds or MRI are possible or not.

3.  Take a record of image tests and inform the doctor.

I’ve asked to change MUGA heart scans to Echos and a CT scan to be an ultrasound to look at the kidneys and the bladder.

If 2000 mSv is the threshold,this means it would take 200 abdominal CT scans and 50 years if I take the scan every three months.

Although I have taken 10 scans in the past 1.5 years, which is a faster pace than this calculation, I think I can conclude that image testing is not something I have to concern about.