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21 November 2009

Answer to Question #5333 Submitted to "Ask the Experts"

Category: Doses and Dose Calculations — Doses from medical sources

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

I'm an x-ray inspector and I was asked about x-ray exposure to an embryo. This is the situation: A patient needed a hip exam. The radiation technologist did two exposures (10-12 mAs and 70-76 kvp). The patient was about two to three weeks pregnant. She received two exposures directly to her pelvic region. I don't know exactly which exams (anteriorposterior, posterioranterior, or lateral) may have been done. How can I calculate the embryo dose?

Since we don't have specific entrance exposure measurements, I will provide values from "typical" exams of this type. The "typical" exam values that have been estimated for a woman in early pregnancy are:

anteriorpolsterior (AP) pelvis - 1.44 mGy (144 mrem)
posterioranterior pelvis - 0.40 (40 mrem)
lateral pelvis - 0.53 (53 mrem)

The AP study will give more radiation, for obvious reasons. So the highest dose will likely be around 3 mGy (300 mrem) if both studies were AP, and the range will be about 1-3 mGy (100-300 mrem), depending on which combination of studies were done. This total dose is comparable to the amount of radiation that the embryo will get from natural (background) radiation throughout a normal period of pregnancy.

Michael G. Stabin, PhD, CHP

Answer posted on 27 March 2006. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of 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 specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.