The Scatterplot Over Time report helps identify unusual patterns or outliers for DIR dose indices. You may elect to plot either the max or total dose index for CTDIvol, Dose Length Product (DLP), or size-specific dose estimate (SSDE).


To access the report, start by clicking Standardized Dose Index Reports from the Interactive Reports submenu, then click on the Scatterplot Over Time tab. You must first select at least one Facility ID and an RPID or Study Description to create a scatterplot.

Note: You may plot only one RPID or Study Description at a time.


The rest of the report filters and parameters are set to default values and may be changed at any time:

  • DIR Measure: Dose Index type CTDIvol, DLP, or SSDE; either maximum value across scans or total for the exam

Note: Maximum and total values are the same for single-scan exams

  • Exam Year and Date Range

  • Age Group

  • Query by: determines whether the RPID / Study Description filter displays standardized RPID exam names or the facility's Study Descriptions

  • Body Part: restricts the RPID / Study Description filter to exams for the specified body part(s)

  • Scanner(s)

  • Benchmarks: Data for the entire registry may be highlighted on the graph. The 75th percentile is selected by default. Only data for the oldest age group are used for benchmarking. Benchmarks are not highlighted in the following cases

    • User selects None

    • No registry benchmarks are available for the selected RPID

    • User selects Study Description for the Query by parameter

Note: DIR benchmarks are available only for scatterplots when Query by is set to RPID because Study Descriptions are not standardized and cannot be aggregated across DIR facilities.


The following example illustrates different features and components of the scatterplot report using the following criteria:

  • Dose Index Type: CTDIVol Max across Scans

  • Age Group: All

  • Exam Year: 2016

  • Date Range: July 1, 2017 to date

  • Scanners: All

  • RPIDs: CT ABD PELVIS W IVCON (RPID145)


DIR SDIR - Sample Scatter Plot 1


The report plots each value of CTDIvol, in mGy, by date. The DIR Benchmarks table lists each age group and number of observations for the facility, and the median and 75th percentiles for the entire registry from the most recent DIR semiannual report. The 75th percentile for the oldest age group, Over 18, also appears  in the chart with a red line and tan background to highlight values above the benchmark.


A total of 650 exams for the facility appear on the plot for exams taken with nine different scanners. The scanner table summarizes the number of observations and minimum, maximum, and average measure values. The table is color coded with red indicating the largest values within each column. Using the color coding we can see the largest mean is 28.7. Clicking on that row highlights the data points for that scanner in the scatterplot, making it easier to see which exams from that scanner are higher than the DIR benchmark.

Note: You can also highlight data by clicking on a scanner in the Scanner Legend.


DIR SDIR - Sample Scatter Plot 2


Although the majority of exams are for adult patients, there are some pediatric exams, as indicated by the age group distribution. Using the Age Group filter, we can restrict the plot to a single pediatric age group, such as the 15-18 group. Doing so also changes the benchmark from 18.3 to 12.2, providing a more useful comparison for these data points.


DIR SDIR - Sample Scatter Plot 3





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