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:

Q

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?

A

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

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