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:
-
In many cases a dose reduction below the DRLs is already possible by optimizing the
examination technique.
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In order to ensure a diagnostic image quality, the control of the image quality is
unavoidable in a dose reduction.
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Through suitable parameter adjustments a compliance with the DRLs is also possible,
using CT devices of older generation without iterative image reconstruction.
Citation Format
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Schäfer SB, Rudolph C, Kolodziej M et al. Optimization of Whole-Body CT Examinations
of Polytrauma Patients in Comparison with the Current Diagnostic Reference Levels.
Fortschr Röntgenstr 2019; 191: 1015 – 1025
Key words
reference levels - dose optimization - whole-body CT - reference mAs
