Answer to Question #14688 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues

The following question was answered by an expert in the appropriate field:

Q

Recently I had a barium swallow fluoroscopy procedure. A Google search prior to the procedure indicated my radiation dose would be about 200 mrem, equivalent to 2 milligray (mGy). This dose is frequently repeated on the internet. A sample article, published on the Medical College of South Carolina website states "For adults, radiation exposure from modified barium swallow studies was very, very low,"…."On average, it was 0.2 millisieverts, which, for perspective, is a lesser amount of radiation than is emitted from a person's body in a year and similar to that associated with living on earth for 32 days."

My procedure report stated I received 0.5 minutes for fluoroscopy for a dose of 50.2 mGy of radiation. So actually, I received 5,000 mrem (equivalent to 50 mGy), which is the dose limit for a US radiation worker. I feel the information on the internet is wrong and needs to be corrected. If I knew the true dose, I would not have had the procedure.

A

I hope that your exam helped in the diagnosis of your medical condition, and you are in good health. As the article you cited states, the "modified barium swallow studies for adults [is] in the very low radiation exposure range and shows there is a very low cancer risk." I would agree and I hope the information below will be helpful.   

In reading your question, I think there is some confusion in your understanding of the dose you received versus statements regarding worker exposure limits and background exposure. This is a common issue as to the units used and to what is being evaluated. 

You write that the exposure you received from your exam was 50.2 mGy. This value refers to the amount of x-ray radiation deposited in the tissues examined under the fluoroscope. Exposure can also be expressed in the older unit of rads. It should be noted that certain organs, such as the brain, large intestines, gonads, etc., were not exposed to x-ray radiation. Alternately, x-ray radiation exposure is called the dose, tissue dose, or effective dose. This x-ray dose is usually expressed in millisieverts (mSv). 

When discussing radiation exposure limits to radiation workers or comparisons to background radiation, values are expressed in millisieverts (mSv) or the older mrem units, where 1 mSv equals 100 mrem. This exposure dose is referred to as the equivalent dose, E. Equivalent dose values are used to compare the exposure the person received to others in a group or the risk of cancer in various organs. The likelihood of cancer developing from radiation exposure differs from one organ to the next. That is, the risk of developing cancer in the bone marrow from radiation exposure is more likely than in the brain from the same exposure. Consequently, a tissue weighting factor, wt, is considered for each typical cancer. The tissue weighting factor for the bone marrow is listed as 0.12, and for the brain it is 0.01. The total of all the weighting factors for the body is 1, as either you get cancer from the radiation exposure or not. The tissue weighting factor is defined here and may be helpful in to understand these concepts.  

For various medical procedures, studies are made to assess the effective dose. This allows for the comparison between different procedures and between different facilities. Relevant to your exam, see "Evaluation of Patient Doses from Upper Gastrointestinal Tract Examinations Based on the Dosimetry in an Anthropomorphic Phantom."

As your reported x-ray exposure was 50.2 mGy, I would say that your effective dose was similar to the value reported in the paper above. The effective dose, however, ranges from 4.0 to 13.4 mSv for hospitals. Taking the average, the value of 8.7 mSv is close to the 6.0 mSv cited for an upper GI exam in Table 2 of the Health Physics Society's (HPS) fact sheet, Radiation Exposure From Medical Exams and Procedures.

As the annual dose from background is about 6.2 mSv, the effective dose of your treatment of 8.7 mSv is approximately one year, five months of background. This differs from the article you cited. I cannot comment on the reason for the differences or on any of the findings you found in Google searches. 

To put your future health risk in perspective, I would point out that "below levels of about 100 mSv above background from all sources combined, the observed radiation effects in people are not statistically different from zero," as stated in the HPS position statement Radiation Risk In Perspective.

I hope this information is helpful.

John Jacobus, CHP

Answer posted on 10 October 2022. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, 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. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.