Answer to Question #2874 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues — Diagnostic X Ray and CT

The following question was answered by an expert in the appropriate field:

Q

I am a recovered sufferer of panic disorder. During the 2002–2003 time frame, I became obsessed with "undiagnosed" symptoms that later were determined to be the result of anxiety/panic attacks. The good news is that I am much better now thanks to getting help from the right medical professional and that there was nothing truly organically wrong with me despite all my symptoms. Here comes the bad news—these symptoms had me in and out of different emergency rooms about every other month and now I am looking back at the amount of testing and radiation and am very concerned about the long-term effects and risk of cancer. For the year 2002–2003, I estimate that I had seven lung CT scans, three V/Q scans, four head CT scans, one abdominal CT scan, and approximately 20 chest x rays.

A

Since you do not have information on the exact equipment used and do not have physicist’s reports of measured radiation output, I have compiled radiation dose estimates from published information.

The US Food and Drug Administration  (FDA) has a website regarding CT scans about whole-body scanning, risk, etc. Although whole-body scanning does not apply to you, the section "Radiation Dose"  has some excellent information regarding radiation risks.

For the list of procedures that you provided, dose estimates can be made.

Procedure Typical ED (mSv)* X Number of Procedures = ED (mSv)
CT chest (lung)(1) 7   7   49
CT head 2   4   8
CT abdomen 8   1   8
Chest x ray 0.02   20   0.4
V/Q scan(1)
(Xe-133 ventilation and Tc-99m MAA perfusion)
2.5   3   7.5
Total Effective Dose from all procedures 72.9

The FDA site listed above gives a typical risk of fatal cancer based on one millisievert (mSv) of effective dose (ED). Specifically, the FDA website states that for a 10 mSv CT scan, the increase in risk of a fatal cancer is 1/2,000. Since your estimated radiation dose is a little over 7 times that dose, the increase risk is approximately 7/2,000.

Keep in mind that the numbers above are for reference only. The radiation doses that you received could be on the order of a factor of 2–3 higher or lower, depending on the equipment used and the settings or technique factors used with the equipment at the time of the exam. The numbers above, however, give you a ballpark estimate of what you are asking for.

Ken "Duke" Lovins, CHP

Reference
Mettler FA Jr., Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic nuclear medicine:  A catalog. Radiology 248 (1) 254–263; 2008.

Editor's Note: The normal incidence of cancer in the United States is approximately 50 percent. For a population of 2,000 individuals, 1,000 would be diagnosed with cancer sometime in their life.  If everyone in the population of 2,000 received 70 mSv, then approximately 1,007 individuals would develop cancer

*Note: To convert to traditional radiation exposure units: 1 mSv = 100 mrem

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 2 October 2003. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.