Too much radiation? Recently, I had a cat scan of my sinuses and a chest x-ray. They are thinking about getting a cat scan of my brain. But to my understanding that's a lot of radiation in a short amount of time. How long are you supposed to wait until th

The . The amount of radiation from ct is certainly higher than from traditional plain film xrays, and you're right to wonder about the risk. However, there are a couple of important issues to consider. First of all, if there's a clinical problem that needs to be sorted out, and if ct is the best way to do that, then the amount of radiation from one additional study is probably not worth worrying about: you're far better off getting a diagnosis that leads to treatment than missing that diagnosis because the full evaluation was not completed. Secondly, you should know that the risk of radiation from cts (and other sources) have to be looked at in both short term and long term perspectives. Without getting too involved in physics, the message is this: a lot of xrays in a short period of time can cause short-term injuries like skin burns and hair loss, whereas a large number of xrays over a lifetime may increase the risk of cancer. It's very unlikely that another ct scan (or even several) right now would cause a skin injury--that's much more likely with image-guided procedures like coronary angiography. On the other hand, your risk of developing cancer from ct imaging (though very small) is the same whether the cts are done all at once or spread out over several years. What it boils down to is this: if your doctor has a specific concern and needs more imaging to make a diagnosis, then getting another ct is probably a good idea. Waiting a while won't make any real difference, except perhaps to delay your treatment. If, on the other hand, he or she is just "covering the bases, " then it may not be worthwhile. You might ask your doctor what, specifically, he or she is looking for and why he or she can't use other tests.
You . You are among an increasingly large number of patients who have very appropriate questions regarding the safety of medical imaging and in particular cat scans (ct scans). The issue is fairly complicated. I often refer my patients to a website that helps to explain the risk of radiation from medical imaging and will also log your exposure. It is a very helpful tool to increase your understanding of the small risks associated with imaging. in general, exposure to radiation from medical imaging increases your lifetime risk of developing cancer. This additional risk is extremely small and increases your risk of developing cancer by an almost negligible amount. To answer your question more pointedly, the risk from multiple exposures of small doses of imaging based radiation does not significantly change with time. Therefore, you do not have to wait between exams.
Risk vs Benefit. Make sure there is good medical necessity before more tests using ionizing radiation. Ct carries the highest dose. Why not a brain MRI instead? But, the risk of the current medical problem may easily outweigh the potential future risk. Almost all data is from nuclear incidents with much higher radiation in 1 large dose. It is difficult to calculate risk at low levels used in ct over months/yrs.