Dynamic changes in murine vessel geometry assessed by high‐resolution magnetic resonance angiography: A 9.4T study

Purpose To establish high-resolution magnetic resonance angiography (MRA) protocols to monitor and quantify dynamic changes of vascular remodeling in pathologic mouse models. Materials and Methods Time-of-flight (TOF) MRA of murine vessels was performed at 9.4T to monitor temporal alterations in the vessel structure in two frequently used injury models (wire denudation of carotid artery and femoral artery occlusion). Quantification of vessel morphology was performed with the use of in-house-developed software and validated by estimation of inter- and intraobserver variabilities and reproducibility, and by correlation with histological data. Results MRA-based volume determination exhibited low intra- and interobserver variabilities and high reproducibility. Furthermore, good correlations with histological data were found four weeks after injury (R2 = 0.970). Two high-resolution image series are presented to demonstrate the applicability of the technique: 1) the time course of a vessel stenosis that reopens by thrombus recanalization, and 2) the continuous restoration of blood flow by collateral vessel formation during arteriogenesis after induction of hindlimb ischemia. Conclusion We describe high-resolution MRA imaging protocols that are suitable for sensitively measuring the extent and time course of changes in vessel morphology in mice in a repetitive manner without any contrast agent. This methodology provides a reliable tool for noninvasive monitoring of vascular lesion development or neovascularization in transgenic mice. J. Magn. Reson. Imaging 2008;28:637–645. © 2008 Wiley-Liss, Inc.