You are here:

Radiology/radiation exposure


Hi Michael,
I have a question regarding radiation exposure. There is a lot of info out there, and most of it is directly contrary (it causes cancer but may also protect cancer, yada yada). My question is two fold: what is your professional take on radiation doses? Also, are women - and people who are small - generally exposed to less radiation during diagnostic procedures than men and people who are overweight?

Also, say that a cancer risk does indeed exist, would getting a heat CT and an abdominal CT be better than getting two CTs directed at the same organ?

I have another question in regards to radiation therapy. I know that involves several thousands of times higher doses than diagnostic radiation. I have a question about whole body radiation. If you have abdominal radiation for, say testicular cancer, does the whole body get some exposure to radiation through scattering?

Sorry one more question...they say that your radiation dosage accumulates over time to gauge a risk for cancer. However, if the body repairs the damage done by radiation immediately after it occurs, how can the dosage be accumulative? It seems like the damage would be repaired by the time more radiation exposure occurred. Is there just fear that - as you get more and more radiation - something will go wrong in DNA repair and up the likelihood of a mutation?  

Sorry for all the questions...I sincerely appreciate your time and knowledge.

Thanks so much,

sorry about the delay in replying. The last week was busy with life happening...

Many points to address so I don't complete answer your questions, please let me know and I'll add to the information.

Radiation dose for diagnostic purposes:
Women are different from men in several ways :) - the most obvious difference is breast tissue so when the breasts are in the field of radiation then they do get a bit more radiation. However, all self respected large centers now scan with bismuth shields during CT over breasts when breasts themselves are not the object of interest.  mammograms are a different story, since breast are of interest then we use xrays to evaluate for them. There is a lot of discussion whether mammograms themselves cause breast cancer because we use radiation....I can tell you honestly that we save 1000s of women every year from dying from advanced breast cancer by screening mammograms and we possible expedite one or two cancers per thousands of women who we screen. and that has never been proven by the way, all of it comes from statistics...  You decide...
the size matters but our newest CT scanners are smart enough to calculate the amount of xray beam based upon your BMI, so large people get slightly more then thin people.
We tend to shield pelvic area in young women and scrotum in young gents because of high physiologic activity during those years in ovaries and testicles...

In a grand scheme of things you want to spread radiation over larger area.  The question about 2 head CTs or 1 head and 1 abdomen doesn't really apply to life. Because if I need to image a head, I am going to image a head and not the abdomen just because I already scanned the head once.  However, your question touches upon two radiation doses: deterministic and stochastic. You can search for it on the web for more information if you are interested.

Regarding scattering: modern equipment has very very little scatter; so presently it does not amount to any significant dose at all.  Radiation therapy has a very focused beam during treatment.

Regarding repair: you are assuming 100% which is probably optimistic.  However, not all DNA damage causes cancer, if fact the change in DNA has to be very very specific and involve specific genes that control cell proliferation.  However, radiation does damage tissue by itself without DNA damage and that tissue can repair itself but not forever...just like patching some point, you can't repair them anymore :)  Certain organs are very sensitive to radiation, the most sensitive is a lens in your eye.

OK, I think I hit the major points. Thanks for the interesting questions! Let me know if I missed anything.



All Answers

Answers by Expert:

Ask Experts


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

©2017 All rights reserved.