Answer to Question #9513 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment/Shielding — Equipment

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


With regard to flouroscopic techniques, how can I convert dose area product (DAP) to exposure area product (EAP)? Is there a conversion factor?


First, the question of how to convert dose area product (mGy per cm2) to exposure area product (R per cm2) can be simplified.

Setting up an equation would give:

mGy cm-2 x X = R cm-2,

where you multiply by a conversion factor, X. 

Before taking up X one can multiply both sides by cm2 to yield:

mGy x X = R.

The question boils down to what is the conversion factor, X between milligray (mGy) and Roentgens (R)? The same factor (X) would be used to convert dose area product in mGy per cm2 to exposure area product in R per cm2.

The absorbed dose in milligray (mGy) is approximately equal to 8.76 times the exposure in R.

So the factor, X is 8.76 and that can be used to convert mGy per cm2 to R per cm2 for diagnostic x rays.

Bushberg JT, Seibert JA, Leidholdt EM Jr, Boone JM. The essential physics of medical imaging, 2nd ed. pg 56; New York: Lippincott Williams & Wilkins; 2002.

National Council on Radiation Protection and Measurements. Structural shielding design for medical x-ray imaging facilities. Bethesda, MD: National Council on Radiation Protection and Measurements; NCRP Report No. 147, pg 2; 2004.

Peter G. Vernig
Radiation Safety Officer

Answer posted on 7 March 2011. 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.