MEASUREMENTS OF TRANSIENT CONTRAST ENHANCEMENT BY LOCALIZED WATER NMR-SPECTROSCOPY

It is shown that a localized spectroscopic method can be used to detec t transient contrast enhancement of transverse relaxation and to measu re cerebral blood volume. High-resolution spectra of the water resonan ce were recorded from small-volume elements of the brain following bol us administration of contrast agents. The integrated signal correspond s to the intensity that would be portrayed in a single voxel in an MR image. The spec tral data can be analyzed to more precisely describe t he alterations in tissue NMR signal incurred by the agent than is poss ible by simple image intensity measurement. In particular, the contrib utions to relaxation by diffusion of water molecules and static line b roadening in the field inhomogeneities generated by intravascular cont rast agents can be separately evaluated from the spectral analysis. Th e method has been used to study rat brain before and during bolus inje ctions of contrast agents, and used to compare the differential effect s of two different agents, viz., Gd-DTPA, and Dy-DTPA. While the integ rated intensity change produced by Dy-DTPA was approximately 35% great er than that for Gd-DTPA, the corresponding linewidths differed by ove r 300%. This method may also provide measurements of changes in tissue oxygenation with high signal-to-noise ratios in brain activation stud ies. (C) 1994 Academic Press, Inc.