What is the fetal dose during a lateral skull examination if the entrance skin exposure is 70 mR?

In a lateral skull examination, the entrance skin exposure (ESE) provides a measure of radiation exposure to the skin of the patient. The fetal dose is typically calculated based on the ESE, however, certain factors determine how much of that radiation actually reaches the fetus.

For a lateral skull X-ray, the fetal dose is significantly low because the direct beam does not penetrate the abdominal area where the fetus is located. Most of the radiation is localized to the head region, and as a result, the dose to the fetus can essentially be considered negligible. It is important to understand that while the entrance skin exposure level might seem substantial, the anatomical positioning during the procedure greatly influences the actual amount of radiation that could potentially reach the fetus.

In this scenario, since the radiation is mainly focused on the head, the expected fetal dose would not be measurable, leading to a calculation of effectively zero mrad. This understanding highlights the importance of considering the radiation scatter, distance from the source, and the anatomical barriers that protect the fetus during such examinations.