TH-EF-BRA-06: A Novel Method of ACR Dose Index Registry Report Interpretation: Population Dose Reduction for Thoracic CT Angiography




To identify a method of ACR Dose Index Registry (DIR) report analysis and interpretation that focuses dose reduction efforts on exams that most affect our patient population.


In place of a direct interpretation of the DIR report, a proposed additional metric — the Total Exposure Variance (TEV) — was calculated for each of the most frequently performed institutional exams. TEV was defined as the product of exam frequency (N) and the difference between institutional and national median dose (CTDIvol or SSDE). TEV indicated total excess institution population dose beyond the equivalent national benchmark. TEV analysis focused investigation of two exams from the 2012 DIR report: 1) CT pulmonary angiography (CTPA), which had SSDE between the median and third quartile; and, 2) CT thoracic angiography (CTTA), optimized for the aorta, which had SSDE in the top quartile.


CT scan parameter changes were implemented lowering the quality reference mAs by 20% and limiting the automatic kV selection range to 100–120. DIR data from July–December 2012 were compared to same time period for 2013. CTPA showed a decrease of median CTDIvol and SSDE of 14% and 16%, respectively, representing a realized decrease in TEV of 1776 mGy-persons. Data for CTTA showed a decrease of median CTDIvol and SSDE of 38% and 44%, respectively, representing a realized decrease in TEV of 1050 mGy-persons. In both cases, the incremental and population dose metrics moved down toward national benchmarks.


TEV analysis used DIR data to shift the paradigm toward reducing population dose instead of frequency-independent interpretation of the report. The TEV metric highlighted exams that would have otherwise been overlooked with direct DIR report interpretation. Recent modifications to the DIR report contents may avail additional approaches to dose reduction.