An imaging technique is proposed in which the contrast is correlated to the morphology of capillaries and other small blood vessels. The technique is based on measurements of the relaxation rates 1/T(2) and 1/T*(2) before and after the injection of a contrast agent. An image is then formed by mapping the quantity Q identical with delta R(2)/(delta R*(2))(2/3), where delta R(2) and delta R*(2) are the changes in the relaxation rates due to the contrast agent. If the contrast agent concentration is sufficiently high, it is shown that Q is given approximately by a simple analytic formula that involves only intrinsic properties of the vascular network and the rate of diffusion. In particular, Q is sensitive to the histologic vessel density. Theoretical predictions for Q are shown to be consistent with experimental data obtained with a rat glioma model and normal cerebral cortex. The imaging technique may be useful in characterizing tumor angiogenesis. Magn Reson Med 44:224-230, 2000.
Copyright 2000 Wiley-Liss, Inc.