Facility comparison reports provide CTDIvol, Dose Length Product (DLP), and Size-Specific Dose Estimate (SSDE) data for your facility compared to the DIR and facilities with the same location type, facility type, Trauma Center Level, and in the same Census Division.


Historically comparison reports were generated on a quarterly basis and distributed in Excel file format. The Excel format has been replaced with three online versions


Data for the above reports are refreshed daily, to provide up-to-date information.



Percentiles and Comparisons

Comparisons with the registry help identify outliers by comparing the facility or corporate account median measure against the registry’s 25th and 75th percentiles. The median is the midpoint between all measure dose levels and the percentiles indicate the portion of exams that had a dose level at or below a certain value. In the example, below, the facility median value of 38.7 indicates that out of 31 exams, approximately half had a dose level below 38.7 and half had a dose above 38.7. For the registry, the 75th percentile indicates that 75% of the 94,687 exams had a dose level of less than 34.7.DIR CT Facility Comparison Sample Snapshot


Put another way, half of the facility’s exams had a dose level above 38.7, which is higher than 75% of all exams for the entire registry, indicating the facility generally has higher dose levels for this Short Name and Age Group.


There are four possible comparison results. These appear as code values for the DIR Standing column in the Facility Excel Report and Corporate Excel Report:

  • Below 25th percentile (DIR Standing code 25): indicates the facility’s median value falls below the 25th percentile for the registry for the selected measure; that is, the facility’s dose levels are generally lower than the entire registry. This is may be good, provided the lower radiation doses are not at the expense of image and diagnosis quality.

  • Between 25th and 75th percentile (code 50): the facility median was between the registry 25th and 75th percentiles; that is, about on par with the registry.

  • Above 75th percentile (code 75): the facility median was above the registry 75th percentile.

  • Insufficient data for comparison (code -9): too little registry data is available for comparison purposes. The registry must have data for at least 100 exams and 10 different facilities at the selected reporting level.

Note: As always, please consult your medical physicist before making any changes to your protocol.



Comparison Data

Exams from a fixed six-month timeframe are used for all comparison groups, including All DIR Sites (registry) and various peer groups (e.g. sites within the same Census Division).  


Although the computations and reporting levels (e.g. by Short Name and Age Group) are similar to those provided in the Summary Comparison Report, the data in the reports will be different because the Summary Comparison Report is refreshed only periodically and its comparisons are made using the same time period  - e.g. a facility’s data for 2018 Q1 is compared to All DIR Sites from 2018 Q1, whereas the online versions use a fixed six-month period for All DIR Sites, as denoted in the report titles.

DIR CT Time Period Titles



Report Short Name and Lookups

Facility and Corporate data are aggregated from the RPID level to a standardized report Short Name. In many cases this aggregation combines RPIDs that are virtually the same or that are sufficiently similar for comparison purposes, to help provide robust data for when comparing data to All DIR Sites and other peer groups.


Each report contains a Short Name Lookups tab which shows how a facility’s RPIDs map to the Short Names in the report, and from which Study Descriptions they came. Below are the detailed descriptions of each column in the table

  • Short Name to look for in report – the Short Name to which RPIDs have been mapped

  • Age Group – mappings are for Adult (Over 18) or Pediatric exams

  • RPIDs used for facility’s statistics – the facility’s RPID mapped to the Short Name

  • Facility Study Description – the exam name mapping (study description to RPID) as defined by the facility

  • RPIDs used for Registry statistics – which RPIDs are mapped to the Short Name across all sites in the registry for the comparison time period.

  • RPID Short Name – the Short Name for the RPID

  • Facility – the individual Facility ID to which the row applies

DIR CT Short Name Lookup Tab



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