Method details

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Quantification of Coronary Arterial Stenosis by Inflating Tubes in CT Angiographic images



Abstract:
Computed tomographic angiography (CTA) is a non-invasive and relatively low cost imaging modality that is employed for stenosis quantification prior to percutaneous coronary intervention (PCI). In this paper we propose a new coronary segmentation method by estimating the likelihood of transversal circles around the manually refined vessel LKEB centerline. A cost function is defined from the similarity of adjacent circles and their likelihoods. The optimal likelihoods are attained from minimization of a functional constrained by prede-fined likelihoods driven from centerline points (internal seeds) and manually se-lected external seeds outside the vessel. Following segmentation, stenoses are detected and graded based on the observed and expected cross-sectional area of the vessel as well as the intensity profile. We applied the developed algorithm on 36 datasets and in case of quantitative coronary angiography (QCA) achieved sensitivity of 63% and positive predictive value (PPV) of 13% for detection of stenosis. The same values for CTA images were 43% and 4%, respectively. The stenosis degree was estimated with an absolute average difference of 46.4% and kappa value of -0.15 as compared to QCA.

Detection confusion tables

Calc. cat.QCA (per segment)CTA (per lesion)
 TPFPFNTP+FPTP+FNTPFPFNTP+FPTP+FN
All  19  183  202  28  24  570  23  594  47 
The results of this method are based on the following centerlines: LKEB team manual.

Detection (QCA per segment / CTA per lesion)

Calc. cat.QCA
Sens.
QCA
P.P.V.
CTA
Sens.
CTA
P.P.V.
Avg. rank
 %rank%rank%rank%rank 
0 (0 - 0.1)  80.0  1.0  9.8  11.0  42.9  7.0  2.5  16.0  8.8 
1 (0.1 - 10)  100.0  1.0  3.7  15.0  20.0  14.0  1.2  16.0  11.5 
2 (11 - 100)  85.7  1.0  10.5  15.0  90.9  2.0  5.3  17.0  8.8 
3 (101 - 400)  50.0  12.0  8.3  19.0  36.8  12.0  4.3  18.0  15.2 
4 (400+)  60.0  4.0  17.6  16.0  60.0  6.0  7.5  16.0  10.5 
All  67.9  4.0  9.4  18.0  51.1  7.0  4.0  18.0  11.8 
For ranking  67.9  4.0  9.4  18.0  51.1  7.0  4.0  18.0  11.8 
These results are based on 30 datasets and 19 submissions.


Quantification

Calc. cat.QCA
Avg. Abs. diff.
QCA
R.M.S. diff.
CTA
Weigthed Kappa
Avg. rank
 %rank%rankΚrank 
0 (0 - 0.1)  47.1  13.0  51.7  11.0  0.01  13.0  12.5 
1 (0.1 - 10)  51.5  15.0  56.3  15.0  -0.01  13.0  14.0 
2 (11 - 100)  53.7  15.0  57.1  15.0  0.01  13.0  14.0 
3 (101 - 400)  50.6  13.0  54.7  11.0  -0.04  14.0  13.0 
4 (400+)  52.9  11.0  56.3  11.0  0.00  14.0  12.5 
All  50.9  14.0  55.0  11.0  -0.02  14.0  13.2 
For ranking  50.9  14.0  55.0  11.0  -0.02  14.0  13.2