Purpose: To evaluate quantitively and qualitatively whether low monoenergetic images at 50 keV demonstrate improved quality compared to conventional images for imaging of acute appendicitis and to assess reader`s preferences.
Material and Methods: A retrospective study of 42 clinically indicated CT exams conducted on a single source DECT (IQON, Philips, Eindohoven) was performed. Patient population was 44 y.o on average (range 18-82), The female/male ratio was 1.4:1, and all had pathologically proven inflamed appendix. A single representative image was chosen from each study and an ROI was drawn along the appendix wall for HU, CNR and SNR values measurements. Comparison of these parameters on the conventional and low monoenergetic images was performed. In addition, all 84 images were randomized, anonymized and presented to two abdominal radiologists; for a 5-point scale quality grading evaluating of the bowel wall thickening, enhancement, conspicuity and mucosal visualization. Lastly, bowel wall enhancement visibility assessment was conducted on conventional and monoenergetic images side-by-side by 3 abdominal radiologists. Paired samples t-tests, a-parametric Wilcoxon test, McNemar test and kappa statistics were used for statistical analysis.
Results: Attenuations of the bowel wall were significantly higher in the monoenergetic images compared to the conventional images, showing increase by a ratio of 1.7 (P<0.05). Significant increase was seen in the SNR (8.88, SD-3.27 vs 5.37, SD-1.84) and CNR (20.96, SD-4.91 vs 14.9, SD-3.04) on the low monoenergetic images as well (p<0.05) compared to the conventional images, by a ratio of 1.4 and 1.6 respectively. In the quality grading mucosal visualization, enhancement and conspicuity showed significantly higher scores by both readers (P<0.05), while bowel wall thickening showed a trend (p=0.229). There was clear preference of the monoenergetic images among all the visibility assessments by all readers.
Conclusions: There is significant and consistent increase in CNR and SNR in the 50KeV monoenergetic images compared to the conventional ones. The monoenergetic images showed significant better visualization of most characteristic active inflammation properties in appendicitis and abdominal radiologists clearly preferred them.
