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Session: Imaging - Cardiac System
Session starts: Thursday 24 January, 13:30
Presentation starts: 13:30
Room: Lecture room 559

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Maartje Nillesen (Medical UltraSound Imaging Centre, Department of Radiology, Radboud University Nijmegen Medical Centre)
Arie van Dijk (Department of Cardiology, Radboud University Nijmegen Medical Centre)
Han Thijssen (Medical UltraSound Imaging Centre, Department of Radiology, Radboud University Nijmegen Medical Centre)
Chris de Korte (Medical UltraSound Imaging Centre, Department of Radiology, Radboud University Nijmegen Medical Centre)

Abstract:
Assessment of right ventricular function is important for clinical decision making in a variety of diseases, such as pulmonary hypertension. With the introduction of 3D real-time echocardiography, accurate volumetric RV measurements might be performed since inadequate assumptions on the geometry of the right ventricle (RV) are not needed. However, (semi-)automated quantification of RV volumes is difficult in 3D echocardiography because of the complex geometry of the RV. Also, RV quantification often strongly relies on implicit knowledge of the global shape of the RV as supplied by expert users. This might introduce errors in RV volume measurement by overlooking true anatomical details. This study describes a fully automated segmentation method for the assessment of RV geometry. This method was developed by the authors originally for left ventricular analysis [1] and as no a priori shape information was incorporated, it could be easily adjusted for RV analysis. Real-time 3D transesophageal echocardiographic (TEE) image sequences of 10 patients undergoing percutaneous cryoablation for atrial fibrillation were acquired in radiofrequency format (RF). A 3D adaptive filtering technique based on the (in)homogeneity of the tissue echo signals that optimizes the discrimination between blood and heart muscle [2] was applied. The filtered data were incorporated in a gradient-based deformable model to segment the endocardial surface. Trabeculations were excluded from the RV volume. End-systolic (ES) and end-diastolic (ED) volumes, as well as ejection fraction (EF) were computed from the segmented endocardial surface and compared against volumes manually delineated by an expert cardiologist. The results show that the method yields good correlation and agreement (ED volume: r = 0.86, mean difference ± standard deviation [-8.7 ± 16.3 ml]; ES volume: r = 0.96, [-4.0 ± 11.2 ml]; EF: r = 0.67, [-0.9 ± 9.8 %]) with respect to the results from the reference contours. The technique prevents incorrect RV quantification caused by strong reliance on geometrical assumptions about average shape of the right ventricle. REFERENCES [1] M.M. Nillesen, R.G.P. Lopata, W.P. de Boode, I.H. Gerrits, H. J. Huisman, J.M. Thijssen, L. Kapusta, and C.L. de Korte, “In vivo validation of cardiac output assessment in non-standard 3D echocardiographic images”, Phys. Med. Biol., 54(7), pp.1951-1962, (2009). [2] M.M. Nillesen, R.G.P. Lopata, I.H. Gerrits, H. J. Huisman, J.M. Thijssen, L. Kapusta, and C.L. de Korte, “Segmentation of the heart muscle in 3-D pediatric echocardiographic images”, Ultrasound. Med. Biol., 33(9), pp. 1453-1462 (2007).