Radiology/CT Safety


QUESTION: Hello. I was wondering if you could answer a question regarding CT safety. A few years ago, I had the following CT Scans and estimated radiation exposures:
CT Abdomen/Pelvis With and without Contrast (30 millisieverts)
Upper GI Series (20 milliesieverts)
Hepatobiliary Scan (5 milliesieverts)
I was unaware that the radiation exposure associated with CT scans were considered a significant risk with regard to potentially causing cancer. I have since read many studies on the issue and have become alarmed. The reputable medical studies I have read seem to indicate that I have significantly increased my risk of deadly cancer as a result of my radiation exposure by as much as 1 in 50 or 2%. This has caused me a great deal of anxiety.

I was hoping to get a general opinion from a radiologist about the risks involved. In my case, my doctor and I knew that my ailment was not life threatening, but still I was in pain and did not know why. That is why I had all the scans. However, I did not realize I was putting my life at risk in agreeing to the scans. I just was hoping to get some comments from a radiologist on this. Do you think that 2% risk of deadly cancer (or any cancer for that matter) is an accurate number? I wish I had not gotten the scans and will certainly be more careful in the future, but now that I have already exposed myself, I would like to get the facts and perhaps try to figure out how to put my mind at ease instead of worrying so much. Thanks.

PS: Since there is risk involved with CT Scans, why would my doctor not have ordered MRI scans instead of the CT scans?

Firstly, the media and internet is full of information blown out of proportion and quite often misleading.  Secondly, while you have a few exams that used radiation, by no means it approaches anything worrisome.  One must always weigh risk vs benefits of the exam. Things like these needs to be on a surface when deliberating when exam is needed. The risk in general population for developing cancer is 50%.

Radiation dose is not simply cumulative. It depends greatly on the organs which are targeting in exam. For example a head CT and a body CT image different organs and therefore, radiation deposited per organ is not cumulative. There are two different ways we account for radiation - stochastic and deterministic. I won't go into details of these as I think it is not necessary to put your worries at ease but if you are still interested just for the sake of being interested you can search these definitions as they relate to radiation exposure.

Another good site to calculate your exposure and how it affects your risk is

I think your estimate of 2% is a gross overestimate.  When we start to worry about medical radiation we talk about tens and tens and tens of CTs scan to the same body area.

Depending on clinical question, MRI is not the best study to look for things.

Hope this helps.

Michael K.

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QUESTION: Thank you so much for your response. It is of great help. Some studies seemed to indicate the risk is more like 1 in 400. Why that may not seem like much I got to thinking that if true that would mean if a hospital gave 400 scans per week, then one person a week could end up getting and/or dying of simply because of diagnostic CT scans. Kind of scary when viewed in that light. I think that some of my concern is because of them doing multiple passes (about 6) over my abdomen area. I understand that those CT scans are some of the more powerful ones and they go over vital organs. Not too many people survive pancreatic cancer. I guess it has kind of amped up my fear knowing those organs got a lot of radiation all at once. I do kind of kick myself because they never found anything wrong with me and the pain finally went away on its own after over a year of problems. It was upper right quadrant pain and its a mystery what it was. But it turns out that was a radiation exposure that was not necessary.

I wouldn't think of it as not necessary exposure.  Normal result is still a result!  What if they would find an early cancer?  would you feel differently then?  of course, you would :)
I would not worry at all about any significant risk from the CT scans.



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Michael K.


Almost any kind of questions regarding any types of radiology exams, procedures, meaning of radiology reports etc...


12 year experience in the field of radiology

American Society of Neuroradiology, Senior Member Society of Pediatric Radiology, Active Member

Radiology Seminars in pediatric neurology American Journal of Roentgenology American Journal of Neuroradiology

Board Certified in Diagnostic Radiology Additional Certificate of Qualification in Neuroradiology

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