Answer to Question #10863 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I am an anesthesiologist, and I once had to “bag” a ventilator patient during a full-body CT (computerized tomography) scan for a critical patient. I wore a lead apron and thyroid shield while bagging the patient at the head of the table during the scan. I am concerned about how much of the dose to the patient I was exposed to, and if the lead provided any benefit.
There are a number of factors in your question that are unknown regarding the radiation dose that you received. The main ones are radiation dose rate (when the CT scan was in progress), where you were standing, and the length of the scan in seconds. The dose rate depends on the technique factors that the scanner used (which can vary from one slice of the scan to the next), the distance you were from the scan plane, and the angle from the central scan axis.
The best way to determine the radiation dose that you receive would be to have a radiation dosimeter on during the time that you are in the CT room during patient scans. Since it sounds as if you did not have a dosimeter, the next best method is to have a measurement performed at the location where you stood, while scanning a CT phantom under similar technique factors that were used on the patient during the procedure when you were in the room.
Since we have no details of technique factors or dose-rate measurements for this situation, it is not possible to determine an estimated radiation dose to a given location for a particular patient scan since measured dose rates vary greatly based on numerous varying factors.
You should contact the radiation safety officer for your institution and ask him/her to determine the approximate radiation dose you received during this study (if you were not wearing a dosimeter). There should be a physics report and survey for each CT scanner that is likely performed on an annual basis. The radiation safety officer or physicist can make that determination from a survey result that may be on file or they can perform a survey under similar conditions to yours to estimate that dose.
Being in the room for one scan in your location will likely result in some measureable radiation dose, but it should not be in the area of the annual radiation dose limit for occupational radiation workers. It is important to note that any person who is in an x-ray room who is occupationally exposed should either have a radiation dosimeter, or there should be documentation on file to show that a dosimeter is not required based on dose history or a calculation.
Many facilities have respiratory therapy technicians in a CT room bagging ventilator patients, and they typically are issued dosimeters and instructed to stand an arm-length away from the patient.
Use of a lead apron while in any x-ray room will significantly decrease radiation dose to areas of the body that are covered, and its use is usually required by state regulations.
Kennith “Duke” Lovins, CHP