X-Ray Dose Comparisons:
X-Ray Program

Among experts there is no universal agreement on whether there is a risk associated with the small amounts of radiation exposure received from medical x-rays and if there is a risk what is the likelihood (probability) of harmful effects arising at some future date. Different methods have been formulated in an attempt to estimate risk. The most widely accepted method, The Linear No Threshold Model, holds that risk is directly proportional to radiation dose. The model is not necessarily accurate, but it is conservative and therefore it is widely used.

Risk to the whole body must be estimated from the x-ray dose administered to a small portion of the body.

This estimate is referred to the Effective Dose Equivalent, EDE.

Using this estimate we can compare x-ray exposures with exposures from natural background radiation. The Background Equivalent Radiation Time, BERT, concept provides a helpful comparison. The BERT value is estimated from the EDE. The EDE for a given procedure is divided by the background radiation level which results in the time required to accumulate a dose equivalent to the EDE. The table list some typical values of EDE and BERT for various procedures.

Background Equivalent Radiation Time

X-Ray Procedure BERT (days) Effective Dose Equivalent (mrem)
Dental 2 1 to 2
Chest 6 1 to 5
Skull 20 10 to 20
Pelvis 65 70 to 140
L-spine 130 130 to 270
Head CT 300 200 to 400
Barium enema 390 510 to 880

If you have additional questions regarding X-rays, please contact DWMRC at (801) 536-0200.