Characterizing Vascular Connectivity from microCT Images Marcel Jackowski 1 , Xenophon Papademetris 1,2 , Lawrence W. Dobrucki 1,3 , Albert J. Sinusas 1,3 , and Lawrence H. Staib 1,2 1 Departments of Diagnostic Radiology 2 Biomedical Engineering 3 Medicine (Cardiology), Yale University, New Haven CT 06520 Abstract. X-ray microCT (computed tomography) has become a valu- able tool in the analysis of vascular architecture in small animals. Because of its high resolution, a detailed assessment of blood vessel physiology and pathology is possible. Vascular measurement from noninvasive imag- ing is important for the study and quantification of vessel disease and can aid in diagnosis, as well as measure disease progression and response to therapy. The analysis of tracked vessel trajectories enables the deriva- tion of vessel connectivity information, lengths between vessel junctions as well as level of ramification, contributing to a quantitative analysis of vessel architecture. In this paper, we introduce a new vessel tracking methodology based on wave propagation in oriented domains. Vessel ori- entation and vessel likelihood are estimated based on an eigenanalysis of gray-level Hessian matrices computed at multiple scales. An anisotropic wavefront then propagates through this vector field with a speed mod- ulated by the maximum vesselness response at each location. Putative vessel trajectories can be found by tracing the characteristics of the prop- agation solution between different points. We present preliminary results from both synthetic and mouse microCT image data. 1 Introduction Methods for the quantification of vascular structure are crucial in a number of domains. While 3D localization and visualization are important, the power of vascular imaging methods lies in quantitative analysis including characterizing and measuring connectivity, level of ramification, segment length as well as cross- sectional area and volume. A particularly important application is the study of changes that occur in response to angiogenic therapy which has tremendous potential for treatment in vessel disease and would benefit from non-invasive methods for quantitative evaluation of vasculature growth and remodeling. X-ray microCT imaging combined with perfused contrast agents provides a robust methodology for evaluation of intact vascular networks [4]. However, the ability to extract and quantify vessels, especially those of smaller diameter, is limited by noise, contrast and extraneous features, such as bone. In CT us- ing contrast agents, vessels appear as relatively bright; in magnetic resonance J. Duncan and G. Gerig (Eds.): MICCAI 2005, LNCS 3750, pp. 701–708, 2005. c  Springer-Verlag Berlin Heidelberg 2005