Gradient-echo and CRAZED imaging for minute detection of Alzheimer plaques in an APPV717I × ADAM10-dn mouse model

Cornelius Faber, Benjamin Zahneisen, Frank Tippmann, Anja Schroeder, Falk Fahrenholz
Magnetic Resonance in Medicine
Published Online: 27 Mar 2007

Different strategies to visualize amyloid plaques with MRI at 17.6 Tesla were investigated in a novel mouse model of Alzheimer's disease (AD). Large iron-containing plaques were observed in the thalamus, but cortical plaques did not show iron deposits. Plaques in the thalamus were visualized in vivo with the use of low-resolution, 3D gradient-echo (GRE) imaging in 82 s, and with 94-m resolution in 34 min. The feasibility of obtaining bright contrast from plaques using the COSY revamped with asymmetric z-GRE detection (CRAZED) technique was investigated in experiments on fixed brains. The original CRAZED approach provided reduced signal near the plaques (similarly to GRE imaging) and additionally emphasized small structures in the brain. In CRAZED images acquired with mismatched gradients, elevated signal near the plaques was obtained, while background signal was suppressed almost to the noise level. Bright-contrast images were acquired in 2.6 min with the use of a 2D GRE sequence with slightly mismatched slice refocusing gradients. For future detection of plaques in patients, such bright-contrast visualization protocols may be of particular value when contrast agents that allow labeling of early plaques with iron oxide nanoparticles become available. Magn Reson Med 57:696-703, 2007. © 2007 Wiley-Liss, Inc.

Indirect detection of NMR via geometry-dependent dipolar fields, revisited

Journal of Magnetic Resonance
In Press, Accepted Manuscript, Available online 1 March 2007,
Wei Dong and CA. Meriles

We explore the dipolar interactions between two separate nuclear spin ensembles in a mixture containing oil and water. Here we expand initial results (C.A. Meriles and W. Dong, J. Magn. Reson. 181, 331 (2006)) to the case in which both systems have the shape of flat, stacked disks. We find that - spite of the strong inhomogeneity of thecoupling dipolar field - the signal encoded in one of the components can be made approximately proportional to the magnetization in the other. This allows us to use one of these systems as a ‘sensor’ to indirectly reconstruct the resonance spectrum or to determine the relaxation time of the ‘sample’ system. In the regime in which dipolar interactions are sufficiently strong, our method can be set to scale-up weaker signals in a non-linear fashion, which, potentially, could allow one to introduce contrast or to improve detection sensitivity of less magnetized samples.