Diagnostic Reference Levels (posted 4/18/2017)

Govdelivery iconThe Radiation Safety Section is considering a move to a different non-regulatory system of comparing patient radiation exposure information measured during our routine inspections.  This is to notify registrants of the pending change and to solicit any concerns about this change. If you have any concerns, please contact us by e-mail at rssinfo@michigan.gov by May 12, 2017.

For many years the Radiation Safety Section has used a set of exposure levels called Standard of Care limits. These limits were set by advisory committees that are no longer in existence.  The Standard of Care limits were last reviewed by an advisory committee in March of 1995.  Many technological changes in imaging have occurred since then and the limits have not been adjusted.

The Radiation Safety Section proposes to stop using the Standard of Care system and start comparing its exposure measurements to Diagnostic Reference Levels (DRL).  As in the case of the Standard of Care limits, DRLs are non-regulatory levels meant to alert a facility that they are using exposures higher than seen in most other facilities.  The use of DRLs has gained favor with several national and international organizations, including the American College of Radiology (ACR) and the National Council on Radiation Protection and Measurements (NCRP).  The DRLs are set at the 75th percentile of the most recently available data.

The table below shows the DRLs calculated from the last five years of data obtained by the Radiation Safety Section from inspections of registered medical and dental x-ray facilities in Michigan.  Each level is presented as an entrance skin exposure in milliroentgens (mR) and entrance skin air kerma in milligrays (mGy).  For computed tomography, each level is expressed as a dose index (CTDIvol) in milligray (mGy).  The table also shows the median exposure or “Achievable Level” for each of the radiographic projections. The achievable level indicates a patient radiation exposure which should be readily attainable since 50% of Michigan facilities are already at this level.

DRL Table