Radiology/Cumulative dose


I am a 65 year old female who had breast cancer in 2008, had a lumpectomy and radiation (25 days).  Subsequently had MUGA scans (4in the course of a year) to follow me on Herceptin.  I currently have an MRI and a digital mammogram once a year each as follow up.  In the past, I have had back and other joint pain and have had numerous Xrays as well as bone densities.  I once also had one of those "total body (CT) scans" as part of a benefit plan.  Lately I have been having leg pain (for the last 2 months, both legs).  My primary care doctor suggested a bone scan.  But I'm nervous and have not booked it yet.  Am I reaching my maximum exposure level?  Isn't radiation cumulative?  Does it matter about the type?  Please help me understand this better.

Hello Gene,

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. I can tell you that a risk of breast cancer is much much higher than a risk of developing cancer from a mammogram. Things like these needs to be on a surface when deliberating when exam is needed.  Also, at age of 65, I would not be greatly concerned that a radiation used in the exam will elevate your risk of developing cancer in a life time; given 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

Hope this helps. . I would book your bone scan and not worry about it.



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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

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