BACKGROUND: Napkin-ring sign (NRS) is an independent prognostic imaging marker of
major adverse cardiac events. However, identification of NRS is challenging because
of its qualitative nature. Radiomics is the process of extracting thousands of quantitative
parameters from medical images to create big-data data sets that can identify distinct
patterns in radiological images. Therefore, we sought to determine whether radiomic
analysis improves the identification of NRS plaques. METHODS AND RESULTS: From 2674
patients referred to coronary computed tomographic angiography caused by stable chest
pain, expert readers identified 30 patients with NRS plaques and matched these with
30 non-NRS plaques with similar degree of calcification, luminal obstruction, localization,
and imaging parameters. All plaques were segmented manually, and image data information
was analyzed using Radiomics Image Analysis package for the presence of 8 conventional
and 4440 radiomic parameters. We used the permutation test of symmetry to assess differences
between NRS and non-NRS plaques, whereas we calculated receiver-operating characteristics'
area under the curve values to evaluate diagnostic accuracy. Bonferroni-corrected
P<0.0012 was considered significant. None of the conventional quantitative parameters
but 20.6% (916/4440) of radiomic features were significantly different between NRS
and non-NRS plaques. Almost half of these (418/916) reached an area under the curve
value >0.80. Short- and long-run low gray-level emphasis and surface ratio of high
attenuation voxels to total surface had the highest area under the curve values (0.918;
0.894 and 0.890, respectively). CONCLUSIONS: A large number of radiomic features are
different between NRS and non-NRS plaques and exhibit excellent discriminatory value.
