Answer to Question #15061 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:

Q

I had a head CT without contrast. My dose report showed a dose length product (DLP) of 1068 milligray centimeters (mGy*cm) and a computed tomography dose index (CTDIvol) of 57.5. How much radiation did I really get? I used different online calculators and each time got a different result. Should I be worried about the radiation amount? I'm 25 years old. I would be grateful for help on this matter.

A

You do not need to be worried about the radiation from the CT scan. One reason different online effective dose calculators give different answers is that effective dose is an estimate based on population average patient sizes and risks. Some of the tissue weighting factors to account for the risk of exposing different tissue types have changed through the years, and not all calculators have updated to the newest values. Don't focus on the exact number that is calculated because it is just an estimate based on the CT machine output for an exposed population. It is not the dose to any individual.

I estimate an effective dose of 2.3 millisieverts (mSv). This is a very low dose, and it doesn't matter whether the estimate is 2.1 or 2.5, the risk is still too low to be observed. Please keep in mind that there is a benefit from the head CT. It gave your doctor information to make an accurate diagnosis and provide appropriate treatment. I hope you are doing well now.

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 15 August 2023. 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.