Confused about patient CT dose limits in Michigan? We hope the information in this post will help clarify the newly established Michigan Diagnostic Reference Level guidelines.
Earlier this year, the Michigan Radiation Safety Section updated guidance on patient CT radiation exposure levels. They have moved from a “Standard of Care” limit guideline to a “Diagnostic Reference Level (DRL)”. The data they use to establish these numbers is collected during their routine inspections throughout Michigan. The DRL is then based on the 75th percentile of the measured exposures for each exam they have listed. For more information on this, please click here!
A specific DRL that may have some Michigan sites confused is the number for a CT Adult Head exam. For a number of years now, sites performing CT (both accredited and not) have been encouraged to meet the American College of Radiology (ACR) Reference Level for Adult Head exams of 75 milliGray (mGy) CTDI. However, the Michigan DRL has now been set at 64 mGy CTDI. Which limit do Michigan CT sites need to meet? First, realize the Michigan DRLs are not regulatory – the 64 mGy is only for guidance. Compliance with these DRLs is not required, only suggested. Therefore, for accreditation purposes for CT Adult Head exams should still not exceed 75 mGy.
That said, CT scanner technology is advancing and many sites using the latest scanners are able to perform CT Adult Head exams below the Michigan DRL guideline of 64 mGy. The danger of dropping the CTDI too far is that image quality will deteriorate and the potential for missing important information increases.
As always, the best method of optimizing the balance between image quality and patient dose is to discuss exam setting options with a team consisting of the radiologist, technologist, CT manufacturer applications specialist, and your MPC physicist. If you have further questions regarding the Michigan Radiation Safety Diagnostic Reference Levels please don’t hesitate to ask your MPC physicist for further clarification.