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Session: Imaging - General
Session starts: Thursday 24 January, 10:40
Presentation starts: 11:55
Room: Lecture room 559

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Pepijn van Horssen (Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands)
Jeroen van den Wijngaard (Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands)
Martin Brandt (Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands)
Imo Hoefer (Department of Experimental Cardiology, Utrecht Medical Center, Utrecht, The Netherlands)
Jos Spaan (Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands)
Maria Siebes (Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands)

Abstract:
Background: An ordered description of the intramural coronary arterial network is essential for vascular tree generation using scaling laws. Knowledge of the intramural vasculature also plays an important role for modeling the transmural blood flow distribution. We investigated the detailed structural organization of coronary arteries and microvessels using an imaging cryomicrotome. Methods: High-resolution registered 3D image stacks of coronary vessels in 8 canine hearts were acquired at 40 µm slice thickness. After skeletonization of the 3D vascular network [1], all branch segments were labeled and connectivity with neighboring segments was determined. Starting from the epicardium, the sub-tree (crown) belonging to each penetrating artery (stem) was identified and the associated perfusion territory was demarcated by 3D Voronoi tessellation, with the endpoints of terminal segments as Voronoi cell centers. The transmural location of the centroid of the Voronoi cell cluster per stem served to classify the perfused crown territory as endocardial, mid-myocardial or epicardial. Vascular volume density was expressed as fraction of vascular volume, comprised of small arteries <400 µm diameter, per total tissue volume within a perfusion territory. Results: Endocardial territories were in the order of 0.57 ml and comprised about 50 per heart, while volumes of the epicardial territories had a median value of 0.029 ml and numbered about 600 per heart. The vascular volume density was 3.2% at the endocardium compared to 0.8% in the epicardium. Accordingly, different scaling law properties for vascular volume vs. tissue mass were derived for these territories. Conclusions: A four times higher volume density of small arteries in endocardial territories may compensate for the stronger flow impediment by extravascular forces due to cardiac contraction, but also entails a larger area at risk for ischemia in case of a proximal stenosis. The resulting different scaling law properties of vascular volume vs. tissue mass per territory type should be taken into account when patient-specific computational models are used to predict coronary perfusion. This work was funded by NHS grant 2006B226 and by FP7-ICT-2007-224495: euHeart. Reference [1] P. van Horssen, J.P.H.M. van den Wijngaard, F. Nolte, I.E. Hoefer, R. Haverslag, J.A.E. Spaan and M. Siebes (2009). Extraction of coronary vascular tree and myocardial perfusion data from stacks of cryomicrotome images. Functional Imaging and Modeling of the Heart: 486-494.