A comparison of three different micro-tomography systems for accurate determination of microvascular parameters P.D. Lee *a , R.C. Atwood a , P. Rockett a , M.A. Konerding b , J.R. Jones a , and C.A. Mitchell c a Department of Materials Science, Imperial College London, London SW7 2BP, United Kingdom; b Dept. of Anatomy, Johannes Gutenberg University, Mainz, D-55099, Germany c University of Ulster, Coleraine, BT52 1SA, United Kingdom; ABSTRACT The investigation of micro-vessel dimensions in 3D is currently problematic due to their complex structures and fine scale. Quantification of vascular parameters is important in several fields of biomedicine; including embryogenesis, wound healing, diseases characterized by uncontrolled angiogenesis (e.g. tumor growth and metastasis) and the development of implantable bio-materials where a functional vascular supply is critical to their successful integration into host tissue. However, techniques that can resolve the micron-scaled features of these capillary beds, such as scanning electron and confocal microscopy, do not allow for total image reconstitution in 3D in thick tissue samples [1]. The present study describes the use of an in vivo corrosion casting technique that provides a stable replica of the microvascular network and the subsequent evaluation of three different µCT systems in order to accurately quantify vessel dimensions. Stable replicas of micro-vascular networks in neonatal mouse eyes were first created using in vivo vascular corrosion casting and then imaged using a unique, laboratory scale, µCT unit. This system combines a LaB 6 cathode with high- performance electron optics to obtain a high resolution x-ray source. Novel image analysis was then applied to the reconstructions to quantify the morphological parameters of the hyaloid vascular plexi in the developing eyes of post- natal day 2 (P2) wild-type mice. These results are compared to synchrotron scans, establishing vascular casting and x-ray µCT as a valid laboratory scale experimental method for accurate 3D quantification of the microvasculature, with potential applications to a wide variety of fields in biological and medical research. Keywords: X-Ray tomography, image analysis, vasculature, tissue scaffolds, corrosion casting 1. INTRODUCTION Vascular development is central to the development and pathophysiology of a wide range of biological phenomena that range from fetal growth to the biocompatibility of engineered implants. In many applications, the vasculature is of a sufficient scale (diameters greater than 50 microns) such that non-invasive techniques (e.g. medical computed-axial tomographic (CAT) scans; magnetic resonance imaging (MRI); or ultrasound scans[1-5]) can be used to characterize vascular development in three dimensions. However, in cases such as retinal development and the early stages of tissue scaffold integration, the scale of the vasculature (diameters less than 20 microns) is too fine to be resolved. Most prior studies of vascularization during fetal retina development have used high-resolution three-dimensional imaging techniques such as scanning electron microscopy (SEM) or laser confocal microscopy. However, although both these methods provide sub-micron scale resolution, the depth of field is insufficient to resolve the complex anatomical structures of interest. Typical examples are found in the developing murine eye where an inner sphere of vasculature known as the tunica vasculosa lentis (TVL) is surrounded and concealed by an outer vessel plexus, the arteria hyaloidea propria (AHP), and in the development of new tissue within a tissue scaffold, where the developing vasculature is surrounded by scaffold material. The structures of interest in a fetal retina are shown in Fig. 1, where both a histological section and SEM micrograph of a wild-type P2 mouse eye are compared. * p.d.lee@imperial.ac.uk; phone +44 207 594 6801; fax +44 207 594 6758; www.imperial.ac.uk/materials Invited Paper Developments in X-Ray Tomography VI, edited by Stuart R. Stock, Proc. of SPIE Vol. 7078, 70780E, (2008) · 0277-786X/08/$18 · doi: 10.1117/12.795558 Proc. of SPIE Vol. 7078 70780E-1 2008 SPIE Digital Library -- Subscriber Archive Copy