Quantitative MRI and Detection of Amyloid Plaques in Alzheimer’s

Early detection of Alzheimer’s may benefit from small voxel-sizes and enhancement of contrast at high field. By direct comparison with histology, our results suggest that amyloid plaque can be directly observed at 14.1T, thus paving the way for clinical applications at 9.4T and below.

Quantitative maps obtained using clinical protocols in vivo at 9.4T in a patient with Alzheimer’s disease and an age and sex matched healthy subjects. Increased QSM and R2* values were observed in the cortex, where most amyloid plaques occur. Cortical QSM values (132x132x610µm3) were 60% more paramagnetic  in the patient than in the control subject, while the more coarsely sampled R2* maps (voxel size:  375x375x1000µm3) revealed values that were ca 16% higher.

Quantitative mapping of magnetic susceptibility (QSM) and the effective transverse relaxation time (R2*) of ex vivo tissue samples were performed at 14.1T with high-resolution techniques and at 9.4T using clinical measurement protocols. Significant differences between healthy controls and patients were found. QSM reflects amyloid plaques ascertained by histology of the same specimens and allows quantification of the amyloid plaque load. Potentially this method could be used for non-invasive diagnosis of Alzheimer’s in vivo at 9.4T, a hypothesis that we are currently investigating.

Histology results evidence the spatial localization of  myelin and amyloid plaques (Aβ) ex vivo. The same tissue specimens were measured with QSM at 14.4T using high-resolution QSM (voxel-size: 37x37x37µm3). The zoomed in areas evidence bright, paramagnetic spots in the upper layers of cortical rim, consistent with amyloid plaques.

1.
Tuzzi, E., Balla, D.Z., Loureiro, J.R.A., Neumann, M., Laske, C., Pohmann, R., Preische, O., Scheffler, K., Hagberg, G.E.:
Ultra-High Field MRI in Alzheimer’s Disease: Effective Transverse Relaxation Rate and Quantitative Susceptibility Mapping of Human Brain In Vivo and Ex Vivo compared to Histology.
. J. Alzheimer’s Dis. 73, 1481–1499, 2020.
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