TH-AB-201-04: Evaluation of a Radiation Dose Control Program Using Exposure Index




Our institution has several Carestream DRX detectors which allow for remote download of exam statistics, including image reject status, body part and projection, and exposure index (EI). The ability to collect exposure information from multiple DR rooms is conducive to a QA program monitoring institutional radiographic exposure levels. Although individual patient entrance skin exposure (ESE) will vary, the radiation dose levels to the detectors are calibrated to be consistent. Our QC program identifies, on an ongoing basis, outliers in practice and opportunities for improvement in institutional radiation dose levels.


Our institution's Carestream digital detectors were configured for remote downloading of exposure statistics. The data is in a spreadsheet format for easy analysis in Microsoft Excel. The EI median and standard deviation were calculated for each protocol (by body part) and histograms were created of EI for high-frequency torso exams, where EI is less sensitive to positioning and dose-reduction methods are most beneficial.


We compared histograms of EI values for different rooms and observed differences of 400+ in average EI (representing 60% difference in radiation levels to the detector) between rooms nominally calibrated to the same EI. We identified distinct contributions to the EI distribution in practice; in some cases different body part projections had central EI values 300 apart, while for other instances peaks were observed at the current calibrated EI, the old calibrated EI, and an EI representing CR techniques.


Our ongoing findings have allowed us to make useful interventions: from emphasizing the use of phototimers instead of institutional memory of manual techniques to identifying unreported problems with phototimer calibration. We believe that this QA program should be simple to implement using Carestream DRX and can reveal problems with radiation levels in the aggregate that are difficult to identify on a case-by-case basis.