The ACR Computed Tomography Dose Index Registry: the 5 million examination update.

The ACR opened the Computed Tomography Dose Index Registry (DIR) for general participation by all facilities in May 2011. Just over 2 years after its launch, the registry has more than 750 registered facilities, 465 of which were actively contributing data at the end of August 2013. The registry has dose index information on 5.5 million CT examinations, which in turn include 9.4 million irradiation events. Participating facilities receive semiannual reports that provide comparisons of dose indices for each procedure relative to all other facilities in the registry and to facilities similar by type and location. The purpose of the registry is to provide facilities a tool to allow them to compare their dose indices with those at peer facilities and make improvements where appropriate. Data on dose indices for all CT examinations are collected and transmitted automatically from each facility to the DIR, after anonymization of data at the site. For each examination, dose indices are compared using volume CT dose index (CTDIvol), dose-length product, and, for body examinations, size-specific dose estimate (SSDE). Fair and meaningful comparison required us to standardize data collection and estimation, procedure nomenclature, and reporting. This article describes the current state of the registry and the implementation of these standards.