Don’t Shield Your Patients Anymore?

In August of this year (2019) the American Association of Physicists in Medicine (AAPM) released a statement that turned a lot of heads.

The AAPM recommends that gonadal shielding (the lead apron around the waist) no longer be used in x-ray imaging exams.  It’s a bold position that goes against what nearly everyone for 100 years has learned to do when getting or taking x-ray images.

Why?  Very simply put, gonadal shielding does very little to reduce x-ray dose and has the potential to increase dose significantly.

How?  The patient’s body, not the x-ray machine, is the primary source of scatter radiation.  The amount of scatter or stray radiation from the x-ray machine itself is quite minimal (not zero – but very small).  Scatter radiation happens as x-rays that entered the body are deflected by encountering the body’s tissues, both hard and soft. The xrays have already entered the body above or below the lead shield. The shield does nothing to radiation from traveling within the body. In fact, it could actually keep scatter radiation from leaving the body by reflecting it back into the patient.

And?  The lead shielding on the patient can actually precipitate harm to the patient or lead to problems that dramatically increase patient dose.  The gonadal shielding can block parts of the patient’s anatomy if it is not placed correctly, and there is always a possibility that something bad or medically relevant was hidden there.  Also, if the lead is blocking something the doctor wants to see, then the x-ray needs to be repeated which automatically doubles the dose to the patient.  Finally, many modern x-ray imaging systems use Automatic Exposure Control (AEC) that adjusts the amount of x-ray being used based on what is in the x-ray field.  If some of the lead shielding is in the x-ray field, then the machine ramps up the x-ray dose.

Now what?  It will take some time to flip the public’s perception of the use of lead shielding on the patient when getting an x-ray.  Certainly patient comfort and stress will play into the decision on whether to use gonadal shielding or not.  The AAPM’s recommendation is to change the default to NO gonadal shielding, rather than defaulting to use the shield.