Answer to Question #14694 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues

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

Q

My young son has significant heart issues. He has needed two cardiac catheterization procedures. His most recent report states that there were two planes (A and B) and provides the following information:

  1. Fluoro time: A-46 min B-40 min
  2. Dose (mGy): A-258 B-674
  3. DAP: A-1375 B-3244
  4. Weight Corrected Cumulative Dose (mGy): A-195 B-509

My research indicated the average amount of radiation received during a cardiac catheterization is 8–20 millisievert (mSv), but my son's report does not include any information in mSv. I did find some websites that state 1 milligray (mGy) equals 1 mSv.

I am confused and would appreciate if you could explain the information and provide me with how much radiation dose my son received.

A

I am so sorry your son has had so many medical procedures. I want to begin by reassuring you that your son did not receive a high dose from this cardiac catheterization procedure.

Dose metrics can be confusing. The unit of absorbed dose is the milligray (mGy). The unit millisievert (mSv) is used for both the equivalent dose—which takes into account the type of radiation; and the effective dose—which takes into account the tissues that are exposed and their sensitivity, averaged across a large population of people. For children, effective dose calculations depend on the patient age and size. When the radiation is x rays, the equivalent dose in mSv equals the absorbed dose in mGy. The effective dose for a medical exam is usually much lower than the equivalent dose because only a small part of the body is exposed. 

To make things more complicated, the dose in mGy that the machine indicates is a measure of the output of the machine measured at a reference point. It is not the patient dose. The dose area product (DAP) can be reported in various units such as gray centimeter squared (Gy cm2), centigray centimeter squared (cGy cm2) or microgray meter squared (µGy m2). We use the DAP and conversion factors based on patient age and size to estimate the effective dose for a cardiac catheterization procedure. Since you did not provide your son's age or weight, I am calculating the effective dose based on an average one-year-old. The effective dose would be lower if he is older and/or larger. The approximate effective dose I calculate is 4.9 mSv based on an article from the British Journal of Radiology. This is very reasonable for a pediatric cardiac catheterization procedure.  

Please keep in mind that there is a very real benefit to your son from having the procedure, and the overall risks are much lower for the catheterization procedure than another surgery. I hope your son is doing well now, and that you will be able to worry less about the radiation he received.

Deirdre H. Elder, MS, CHP, CMLSO

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 14 December 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.