Since 2011, the American College of Radiology's Dose Index Registry (DIR) has helped clinicians and facilities improve the quality of patient care by collecting computed tomography (CT) dose indices data through automated data transmission and leveraging that data to provide feedback to participants and establish national benchmarks.

Data Collected

The DIR CT module automatically de-identifies exam data sent directly to the registry to include Volume CT Dose Index (CTDIvol) and Dose Length Product (DLP). In addition, DIR CT also computes size-specific dose estimate values (SSDE), for body examinations, that more accurately represent the radiation dose absorbed by the patient, based on patient size.  

Currently, exam descriptions are standardized, using RadLex Playbook procedure names, so that data are comparable across facilities and scanners.  

Note: Plans call for the DIR CT module to implement the ACR Common  collection of common radiology terms and semantic structures to facilitate rapid standardization of terminology for ever-expanding radiology exams and procedures.  ACR Common will link where possible and appropriate to existing terminologies, such as Radlex Playbook.

DIR US DRL and AD for 10 Adult CT ExamsThe large volume of data collected allows the DIR CT to provide feedback reports segmented by adult and pediatric populations, with pediatric data segmented into five distinct age groups.

DIR CT dose information has helped improve patient care nationally through the ACR’s development of size-specific Diagnostic Reference Levels (DRLs) and Achievable Dose (AD) guidelines for the 10 most common adult CT examinations.   

Facilities can use the DRLs and ADs as quality checks to ensure patients receive the optimal radiation dose.

Available Reports  

Participants submitting DIR CT data can view and analyze performance data available in a variety of interactive reports and in an executive summary report published quarterly. Facility comparison reports provide measure performance data for your facility compared to the DIR and facilities with the same:  

  • Facility type (e.g., freestanding vs. community hospital)

  • Location (metropolitan, suburban, or rural) 

  • Geography (Midwest vs. Mid-Atlantic) 

Comparisons allow facilities to identify dose outliers, by exam, so they can focus on reducing radiation exposure while maintaining image quality.


Several Knowledge Base articles are available to help you become familiar with reports. 

Getting Started 

The DIR Start-up Guide describes a  step-by-step process for DIR participation—from assembling your team to reviewing your reports.   

Already a NRDR participant? Add the DIR to your facility registration . Only one registration is required to participate in any of the DIR modules. 

Last reviewed: 05/06/2021