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08 February 2012

Answer to Question #5952 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:

I was wanting to know how much the amount of radiation exposure for a medical x ray had changed over the years, in particular from the 1950s to now (on average, I only want a general idea). I have had a fair amount of x rays over the years, but I find that doctors never ask my radiation history when advising me to have more x rays. What is the cumulative effect of x-ray radiation?

This is an interesting question and it is made even more interesting by the fact that I could really find nothing in the literature that gave me absolute numbers related to how radiation doses for medical x rays have changed over time.

There are a number of things that have been done to decrease radiation dose (faster films, faster screens, fluoroscopy that is on only intermittently, x-ray tube and collimator shielding, etc.) over the past half-century in addition to an increased number of regulations on how much radiation an x-ray machine can emit. For a given exam—say a five-picture lumbar spine—the overall dose a patient would receive from that exact exam has decreased. By how much? I don't know and, if it is in the literature, I'm unable to find one actual number.

Now that being said, many types of diagnostic exams like a five-picture lumbar spine are now being done using CT (computerized tomography) scanning techniques. This type of exam gives more information, but it can also increase patient dose.

With enough radiation dose, generally more than obtained for routine diagnostic exams, the cumulative effect can be an increased risk of cancer in your lifetime. Whether there would be an increased risk is dependent on the total radiation dose from all exams, the rate at which you got that dose (how many exams each year), and how those exams were performed (the settings on the x-ray machine). It also depends on how old you were when you got those exams. If you were a child, chances are greater that you have an increased risk. If you were older, chances are less.

Kelly Classic
Certified Medical Health Physicist

Answer posted on 16 November 2006. The information and material posted on this website is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of 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 specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Website. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.