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DRC Home > X-Ray Section > Dose Comparisons

X-Ray Section: X-Ray Dose Comparisons

C-spine Chart (click to view full size) C-spine Chart (click to view full size) C-spine Chart (click to view full size)

X-ray Dose Comparisons.Among experts there is no universal agreement on whether there is a risk associated with the smallamounts 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. C-spine Chart (click to view full size)

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)

1 to 2
1 to 5
10 to 20
70 to 140
130 to 270
Head CT
200 to 400
Barium enema
510 to 880

If you have additional questions regarding X-rays, please contact a member of the X-ray staff at 801-536-4250 or you may contact us through e-mail.