Matts Karlsson

Time resolved three-dimensional automated segmentation of the left ventricle

This paper describes a robust approach for multimodality segmentation of the cardiac left ventricle. The method is based on the concept of deformable models, but extended with an enhanced and fast edge detection scheme that includes temporal information, and anatomical a priori information. The algorithm is implemented with a fast numeric scheme for solving energy minimization, and efficient filter nets for fast edge detection. This allows clinically applicable time for a whole time resolved 3D cardiac data set to be achieved on a standard desktop computer. The algorithm is validated on images acquired using MRI gradient echo, MRI (SSFP) images, and Cardiac CT The complete algorithm is implemented into a software package freely available for non commercial research at http://segment.heiberg.se

Pitfalls in Doppler Evaluation of Diastolic Function: Insights from 3-Dimensional Magnetic Resonance Imaging

Ultrasound-Doppler assessment of diastolic function is subject to velocity errors caused by angle sensitivity and a fixed location of the sample volume. We used 3-dimensional phase contrast magnetic resonance imaging (MRI) to evaluate these errors in 10 patients with hypertension and in 10 healthy volunteers. The single (Doppler) and triple (MRI) component velocity was measured at early (E) and late (A) inflow along Doppler-like sample lines or 3-dimensional particle traces generated from the MRI data. Doppler measurements underestimated MRI velocities by 9.4% +/- 8.6%; the effect on the E/A ratio was larger and more variable. Measuring early and late diastolic inflows from a single line demonstrated the error caused by their 3-dimensional spatial offset. Both errors were minimized by calculating the E/A ratio from maximal E and A values without constraint to a single line. Alignment and spatial offset are important sources of error in Doppler diastolic parameters. Improved accuracy may be achieved with the use of maximal E and A velocities from wherever they occur in the left ventricle.

Chapter 35 Closure and Animations

Leaflet shape change in each heart was quantified by fitting (as described in Appendix C) a best-fit plane to all anterior leaflet markers for each frame (f) in the three consecutive beats studied. The distance (Z) from each anterior leaflet marker (m) to this plane in each frame Z(f,m) was then obtained. A systolic average, Zavg(m), was then obtained for each leaflet marker using all frames from mitral valve closing (MVC) to opening (MVO) for all three beats. For each frame, and each marker, the difference Z(f,m)-Zavg(m) was then computed and squared. The square root of the mean of these differences for all markers was then obtained for each frame as Zrms(f).In this chapter, we visualize the valve along the Z-axis for the six hearts H1-H6, looking from the left atrium toward the left ventricle, clamping the best-fit annular plane to the X-Y axis. All s ...Competent mitral valve closure requires tight coaptation of the edge surfaces of the anterior and posterior leaflets. This chapter explores the precision with which specific sites on these surfaces ...Figures 35.1-35.6 display mitral valve annular and leaflet geometry snapshots from the animations provided in Appendix D for specific instants associated with left ventricular inflow and pressure from peak diastolic inflow through valve closure and early left ventricular systole for hearts H1-H6 (data in Appendix A).The stiffening twitch of the annular half of the anterior mitral leaflet at the beginning of each beat likely arises from P-wave-stimulated, β-dependent, neurally-insensitive myocytes located in ...Each posterior leaflet annular radiopaque marker was surgically placed under direct observation at the posterior leaflet hinge points, where tissues associated with the left atrium and left ventric ...The anterior commissure is the junctional region between the anterior leaflet and the P1 scallop of the posterior leaflet (Markers 1, 2, 3, and 16 in Figure 38.1; fold 3 in Figure 27.1). Figures 38 ...In this chapter, we explore one of their likely functions. In future chapters, we examine additional functions.xa0A trampoline is a device that stretches a material taut with forces from peripheral r ...In Chapter 24 we noted that the posterior leaflet edge perimeter changes by a mean value of 32 mm throughout the cardiac cycle, while the mitral annular perimeter changes by 13 mm and the anterior ...Throughout left ventricular systole, with the mitral valve closed, pulmonary venous flow fills the left atrium, presumably stretching and storing potential energy in the left atrial walls. During e ...In this and the next several chapters we conduct a more complete study of the dynamics of the posterior leaflet(s) employing datasets from hearts with 9 markers on the posterior leaflet edges and 1 ...Figure 3.1 illustrates the geometric relationships between the LFT (Marker#29), APT (Marker#31), SH (Marker#22), RFT (Marker#24), and PPT (Marker#33) for diastole (left panel) and systole (right panel).The following are brief summaries of concepts underlying normal mitral valve mechanics that we find most compatible with the currently available data. Chapters developing and supporting these conce ...Figure 1.1 is a view from a 3-D rendering of systolic geometry for the left ventricle, mitral valve, and aortic valve, computed as a composite from two experiments involving precise measurement of 83 marker sites. The methods used to obtain this 3-D dataset, including the full dataset file, are outlined in Appendix B. Note that in this systolic rendering, the aortic valve is open and the mitral valve is closed.The concept of the closed mitral valve forming a tent-like structure is well-known in the literature. The mitral annulus forms the floor of the tent and the leaflets form the tent walls that ex ...Here, we describe an attempt to model, as accurately as possible in 3-D space, the geometric relationship between the various components of the left ventricle, the mitral valve, and the aortic valv ...In this chapter we explore the opening and closing behavior of the anterior and posterior leaflets whose hinge regions define the mitral annulus.