title: Improving CCTA-based lesions' hemodynamic significance assessment by accounting for partial volume modeling in automatic coronary lumen segmentation.
abstract: OBJECTIVE
  The goal of this study was to assess the potential added benefit of accounting for partial volume effects (PVE) in an automatic coronary lumen segmentation algorithm that is used to determine the hemodynamic significance of a coronary artery stenosis from coronary computed tomography angiography (CCTA).
  
  
  METHODS
  Two sets of data were used in our work: (a) multivendor CCTA datasets of 18 subjects from the MICCAI 2012 challenge with automatically generated centerlines and 3 reference segmentations of 78 coronary segments and (b) additional CCTA datasets of 97 subjects with 132 coronary lesions that had invasive reference standard FFR measurements. We extracted the coronary artery centerlines for the 97 datasets by an automated software program followed by manual correction if required. An automatic machine-learning-based algorithm segmented the coronary tree with and without accounting for the PVE. We obtained CCTA-based FFR measurements using a flow simulation in the coronary trees that were generated by the automatic algorithm with and without accounting for PVE. We assessed the potential added value of PVE integration as a part of the automatic coronary lumen segmentation algorithm by means of segmentation accuracy using the MICCAI 2012 challenge framework and by means of flow simulation overall accuracy, sensitivity, specificity, negative and positive predictive values, and the receiver operated characteristic (ROC) area under the curve. We also evaluated the potential benefit of accounting for PVE in automatic segmentation for flow simulation for lesions that were diagnosed as obstructive based on CCTA which could have indicated a need for an invasive exam and revascularization.
  
  
  RESULTS
  Our segmentation algorithm improves the maximal surface distance error by ~39% compared to previously published method on the 18 datasets from the MICCAI 2012 challenge with comparable Dice and mean surface distance. Results with and without accounting for PVE were comparable. In contrast, integrating PVE analysis into an automatic coronary lumen segmentation algorithm improved the flow simulation specificity from 0.6 to 0.68 with the same sensitivity of 0.83. Also, accounting for PVE improved the area under the ROC curve for detecting hemodynamically significant CAD from 0.76 to 0.8 compared to automatic segmentation without PVE analysis with invasive FFR threshold of 0.8 as the reference standard. Accounting for PVE in flow simulation to support the detection of hemodynamic significant disease in CCTA-based obstructive lesions improved specificity from 0.51 to 0.73 with same sensitivity of 0.83 and the area under the curve from 0.69 to 0.79. The improvement in the AUC was statistically significant (N = 76, Delong's test, P = 0.012).
  
  
  CONCLUSIONS
  Accounting for the partial volume effects in automatic coronary lumen segmentation algorithms has the potential to improve the accuracy of CCTA-based hemodynamic assessment of coronary artery lesions.
authors.affiliation: Philips Medical Systems Technologies Ltd., Advanced Technologies Center, Haifa, 3100202, Israel.
authors.forename: Moti
authors.initials: M
authors.lastname: Freiman
authors.affiliation: Philips Medical Systems Technologies Ltd., Advanced Technologies Center, Haifa, 3100202, Israel.
authors.forename: Hannes
authors.initials: H
authors.lastname: Nickisch
authors.affiliation: Philips Medical Systems Technologies Ltd., Advanced Technologies Center, Haifa, 3100202, Israel.
authors.forename: Sven
authors.initials: S
authors.lastname: Prevrhal
authors.affiliation: Philips Medical Systems Technologies Ltd., Advanced Technologies Center, Haifa, 3100202, Israel.
authors.forename: Holger
authors.initials: H
authors.lastname: Schmitt
authors.affiliation: Philips Medical Systems Technologies Ltd., Advanced Technologies Center, Haifa, 3100202, Israel.
authors.forename: Mani
authors.initials: M
authors.lastname: Vembar
authors.affiliation: Philips Medical Systems Technologies Ltd., Advanced Technologies Center, Haifa, 3100202, Israel.
authors.forename: Pál
authors.initials: P
authors.lastname: Maurovich-Horvat
authors.affiliation: Philips Medical Systems Technologies Ltd., Advanced Technologies Center, Haifa, 3100202, Israel.
authors.forename: Patrick
authors.initials: P
authors.lastname: Donnelly
authors.affiliation: Philips Medical Systems Technologies Ltd., Advanced Technologies Center, Haifa, 3100202, Israel.
authors.forename: Liran
authors.initials: L
authors.lastname: Goshen
mesh_terms: D019540:Area Under Curve; D000072226:Computed Tomography Angiography / Q000379:methods*; D017023:Coronary Angiography / Q000379:methods*; D023921:Coronary Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000503:physiopathology; D066264:Datasets as Topic; D006439:Hemodynamics; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D000069550:Machine Learning; D008955:Models, Cardiovascular; D010363:Pattern Recognition, Automated; D012372:ROC Curve; D012189:Retrospective Studies; D012984:Software
keywords: coronary CT angiography; coronary artery disease; fractional flow reserve simulation; partial volume effect; segmentation