The Scatter Plot Over Time report is a useful way to view your data over time and quickly spot unusual patterns or outliers, as well as for determining if your CT scanners have been sending localizers (often referred to as topograms or scouts). The report graphs data for one of three units of measure: CTDIvol, DLP, and SSDE.


After logging in to the report tool, select Scatter Plot Over Time to open the report filter. You can filter the report by

  • Data Type (unit of measure): CTDIvol, DLP, SSDE; either maximum value across scans or total for the exam

  • Age Group

  • Exam Date Range

  • Scanner(s)

  • Exam Type, using either RadLex Playbook IDs (RPIDs) or your facility’s Study Descriptions


The following examples illustrate different ways to create and use the scatter plot report.



Example 1: Scatter Plot Over Time with CTDIvol, RPIDs, and Adult & Pediatric Search

This example demonstrates one way to identify outliers for a subset of exams. The scatter plot, below, was generated using the following criteria:

  • Data Type: CTDIvol Max across scans

  • Age group: Adult and Pediatric

  • Date Range: July 1, 2017 to date

  • Scanners: All (scanner names blurred out)

  • RPIDs: Abdominal exams

    • RPID3 CT ABD WO IVCON

    • RPID4 CT ABD WO & W IVCON

    • RPID5 CT ABD W IVCON

Note: RPID search criteria are limited to three RPIDs.

DIR SDIR - Sample Scatter Plot 1


The visual display plots each value of CTDIvol, in mGy, by date. Although both Adult and Pediatric age groups were selected, data are available for Adult exams only. The list of scanners selected as search criteria appears beneath the graph.

Note: This does not mean that all scanners in the display contributed data. It is only a confirmation of the search criteria.


Click the Large Image link to view an enlarged version of the report.


When RPID values are used for exams (as opposed to Study Descriptions), each value is assigned a marker to indicate which RPID it represents, as highlighted in the red box, below. The legend includes the median values across all DIR participants from the most recent aggregate report for each RPID. The median values are displayed as horizontal lines across the graph, making it easy to identify outliers for each RPID. In this example, the DIR’s median values for RPIDs 3, 4, and 5 are 13.65, 14.73, and 11.76, respectively, as of the last report from June, 2017. While most of the exams for this facility are less than 30 mGy, there are some outliers above 40 mGy, well above the median values for each RPID.

DIR SDIR - Sample Scatter Plot 2

Note: DIR median values are available only for scatter plots with RPID criteria because Study Descriptions are not standardized and cannot be aggregated across DIR facilities.



Example 2: Scatter Plot Over Time with CTDIvol, RPIDs, and Pediatric Search

The second sample report is for pediatric exams and was generated using the following criteria:

  • Data Type: CTDIvol Total for exam

  • Age Type: Pediatric, all age groups

  • Date Range: January 1, 2017 to present

  • Scanners: All

  • RPIDs: Brain exams

    • RPID265: CT HEAD BRN W IVCON

    • RPID266: CT HEAD BRN WO IVCON

    • RPID267: CT HEAD BRN WO & W IVCON

DIR SDIR - Sample Scatter Plot 3

Notice that, for pediatric reports, both the search criteria and report data are grouped by age. The sample report, above, shows most exams (99) were for the 15 – 18 age group, while the 3 – 6 age group had the fewest (9). The DIR median values for the select RPIDs are for all pediatric age groups combined, so it is worthwhile to further restrict the report criteria by age group to do deeper analysis.



Example 3: Using an SSDE Scatter Plot to Demonstrate Lack of Localizers

In our third example, we created a scatter plot of CTDIvol Total for Exam for three RPIDs for all adult and pediatric exams since October 1, 2017, using data from all scanners. The chart shows exams for eight days.

DIR SDIR - Sample Scatter Plot 4


Next, we changed the Data Type to SSDE Max across scans, leaving all other criteria the same. However, the report query returned the message No records found, even though we know there are exams present, based on the query for CTDIvol Total for exam, above. This indicates that the facility’s scanners did not send localizers for these exam types during this time period. Localizers are used to compute SSDE for body exams. Therefore, the fact we have report data for Data Type = CTDIvol, but no data for Data Type = SSDE indicates we are missing localizers for these exams.

DIR SDIR - Sample Scatter Plot 5

Note: SSDE is not available for head exams.



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