Answer to Question #12472 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:


I had two arm x rays and I think my head was within 50–100 centimeters from the x-ray tube. Is my head at risk?


No, your head is not at risk. 

On an overhead radiographic unit there are two major components (1) the x-ray tube and protective housing, and (2) the variable-aperture collimator. The protective housing has a window through which the x rays are emitted. In all other directions, the protective housing is constructed with radiation absorbing material (e.g., lead). 

Affixed to the window of the x-ray tube protective housing is the variable-aperture collimator. This device allows the technologist to adjust the actual size of the x-ray beam to only the area of interest by manipulating two pair of shutters in two dimensions (the length and width of the x-ray beam). 

These devices are designed to shape and direct the x-ray beam to one direction as it comes out the bottom of the collimator. The amount that "escapes" through the shielding of the protective housing and the collimator (called leakage radiation) is a very small fraction of the useful beam. The permissible amount of leakage radiation is regulated by U.S. Food and Drug Administration and State regulations. It is checked during equipment inspections performed by diagnostic imaging physicists and State inspectors. 

The bottom line is that any radiation that your head received would be very small and completely inconsequential.

Kent Lambert
Certified Health Physicist
Fellow, Health Physics Society

Answer posted on 6 July 2018. 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.