Answer to Question #13689 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:


My test was a typical fluoroscopy diagnostic exam. I was provided the following information about my radiation exposure from the exam:

  • The fluoroscopy on time was 2.7 minutes with a dose area product (DAP) of 18.167 Gy-cm2
  • Total dose was 142.988 mGy
  • The skin surface dose was 0.17 Gy

Are the skin-surface dose and total dose the same thing? Could you please help me to estimate the effective dose based on the DAP?


The skin-surface dose and the machine-reported total dose from the equipment are not necessarily the same. The skin dose can be higher when the distance from the x-ray tube to the skin is less than the distance to the reference point for the system.

With the information provided, I estimate that the effective dose is between 4.5 and 6.8 mSv. Effective dose is a population average—not the dose to an individual patient. The risk from the radiation is either too low to measure or doesn't exist. 

Deirdre H. Elder, MS, CHP, CMLSO

Answer posted on 27 October 2020. 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.