Answer to Question #10276 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
Lead-lined caps are becoming popular with cardiologists and interventional radiologists to protect the skull. There is a concern that without the lead-lined caps, there is an increase of brain cancer among these workers. I was told if the cap is not worn correctly to cover the frontal bone down to the eyebrow, the incident scatter photon can enter through the frontal bone, "rebound" off of the back of the skull, bounce around causing more damage than if the worker was not wearing the lead-lined cap. Is this true? Is there any literature I could read on this?
The brain has a very low risk of developing cancer from radiation exposure. International Commission on Radiological Protection (ICRP 103) assigns the risk of brain cancer from radiation exposure a very low weighting factor, compared to other tissues.
If appropriate suspended shielding is used, there should be no need for a lead-lined cap. However, suspended shielding is a must in an interventional imaging facility.
The recently published National Council on Radiation Protection and Measurements (NCRP) Report 168 (Radiation Dose Management for Fluorscopically-Guided Interventional Medical Procedures) emphasizes the use of portable (suspended) barriers. It shows that a suspended barrier, if properly used, provides protection to not just the head but the also the neck and upper chest areas. There is no discussion of lead-lined caps in NCRP Report 168. Portable shielding will be much more effective since it contains two to four times the amount of lead compared to lead-lined caps.
Wherever tissue is exposed to radiation, scatter photons are produced. The scattered photons inside the body are also scattered. However, the amount of secondary scatter is very low and, typically, not of concern. This is true if the person is wearing a lead-lined cap or not. The lead-lined cap reduces the scattered x rays from the patient, but will have no impact once the x rays interact with the body of the staff. It seems that wearing the lead-lined cap the way you describe would be extremely uncomfortable and annoying.
Personally, I see no need for a lead-lined cap, since the amount of scattered radiation to the head should be low with the appropriate portable lead shielding.
Joel E. Gray, PhD