title: High-resolution MR imaging of mouse brain microvasculature using the relaxation rate shift index Q.
abstract: Magnetic resonance imaging (MRI) is a powerful method for in vivo quantification of tissue properties. It has been previously proposed that the index Q identical with Delta R2/(Delta R2*)2/3, where Delta R2 and Delta R2* are the spin echo and gradient echo relaxation rate shifts caused by the injection of an intravascular contrast agent, may be useful for characterizing microvasculature. In particular, Q is expected to correlate well with the density of microvessels. This study presents high-resolution in vivo Q-maps of normal mouse brain obtained with a superparamagnetic iron oxide contrast agent at a field of level of 9.4 T. Normative Q values are derived for several regions of interest and significant interregional variations are observed. Microvessel densities estimated from the Q-maps are found to be in reasonable accord with histologically determined values. A possible application of Q-maps is the assessment of angiogenic activity in tumors.
authors.affiliation: Jockey Club MRI Engineering Centre and Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, People's Republic of China.
authors.forename: Ed X
authors.initials: EX
authors.lastname: Wu
authors.forename: Haiying
authors.initials: H
authors.lastname: Tang
authors.forename: Jens H
authors.initials: JH
authors.lastname: Jensen
mesh_terms: D000818:Animals; D001921:Brain / Q000033:anatomy & histology* / Q000098:blood supply*; D002560:Cerebrovascular Circulation; D003287:Contrast Media; D005290:Ferric Compounds; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D008833:Microcirculation / Q000033:anatomy & histology*
chemical_list: D003287:Contrast Media; D005290:Ferric Compounds; C000499:ferric oxide