Optimization of Whole-Body CT Examinations of Polytrauma Patients in Comparison with the Current Diagnostic Reference Levels

Abstract

Purpose Evaluation of the dose values of a polytrauma whole-body CT examination used in clinical practice with regard to the 2016 updated diagnostic reference levels and reduction of the mean exposure levels using simple optimization steps. Materials and Methods In each case, 100 exposure values before and after dose optimization were compared with the old and new diagnostic reference levels. The grayscale values and the signal-to-noise ratio (SNR) were determined for the lung, the aortic arch and the liver. A visual assessment of the image quality was performed by two radiologists on the basis of a Likert scale (0 – non-diagnostic, 1 – poor visualization, 2 – moderate visualization, 3 – good visualization, 4 – excellent visualization) for CT examinations both before and after optimization. Results The acquired exposure values after dose optimization were below the old and new diagnostic reference levels (1319.98 ± 463.16 mGy · cm) while the mean value of the exposure values before optimization (1774.96 ± 608.78 mGy · cm) exceeded the current diagnostic reference levels. The measured grayscale values (HU) were (before versus after optimization): lung – 833 HU vs. – 827 HU (p = 0.43), aortic arch 341 HU vs. 343 HU (p = 0.70) and liver 68 HU vs. 67 HU (p = 0.35). After dose optimization the SNR in the lung was minimally higher, while it was minimally lower in the two other regions than before the optimization. Visual assessment of the image quality showed almost identical values with 3.85 evaluation points before and 3.82 evaluation points after dose optimization (p = 0.57). Conclusion Due to the updating of the diagnostic reference levels, an analysis of the own exposure values is necessary in order to be able to detect high values promptly and to initiate appropriate measures for dose reduction. Appropriate adaptation of the examination parameters with consideration of the necessary image quality allows a significant reduction of the radiation exposure in most cases, also on CT devices of older generations. Key Points: Citation Format