Answer to Question #14797 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues

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

Q

What is the difference between DLP and effective dose, and why is there some hesitation about the use of effective dose?

A

Dose-length product (DLP), in units of milliGy–centimeters (mGy·cm) is a metric related to the amount of radiation a patient has received. When a correction factor is used, you can convert DLP to effective dose. See ATE Q/A 11118.

You asked why there is hesitation to use effective dose when talking about patient exposures. Effective dose was never meant to be used to calculate individual patient risk from radiation exposure. The factors used in the effective dose calculation are based on epidemiology data from radiation workers (like x-ray technologists) and it was developed to be used to establish and assess worker radiation exposure limits.

While it is possible to calculate an effective dose value for an individual patient, the effective dose concept was not designed for individual risk assessments or to assess patient exposures. Calculating a cancer risk from effective dose can be done using a factor corresponding to a hypothetical risk. This is by no means an exact science. Keeping in mind that about 40% of people will develop cancer in their lifetime scientists estimate that the increased risk of developing cancer from receiving 100 mSv of radiation is about 0.5%. See the American Cancer Society website.

Therefore, if a person is exposed to 100 mSv, their lifetime risk of developing a cancer is approximately 40.5%. Most scientists agree that the potential effects of cumulative doses less than 50 mSv are so low they are considered negligible.

Linda Kroger, MS

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 9 January 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.