Keywords:
Anatomy, Head and neck, MR, Image manipulation / Reconstruction, Imaging sequences, Dementia
Authors:
E. Tuzzi, G. E. Hagberg, A. Loktyushin, R. Pohmann, K. Scheffler; Tübingen/DE
DOI:
10.26044/ecr2019/C-2185
Methods and materials
Four patients with Alzheimer’s Disease (AD) were scanned at 9.4T using a multi-echo (N=6) 3D-GRE sequence (0.375x0.375x0.8mm3 voxel size,
TR=42ms; TE=6 to 30ms in steps of 6ms,
TA=9min,
FOV=192x174x70.4mm3,
matrix size=512x464x88).
An FID navigator was acquired before the phase-encoding and readout pre-winding gradients,
with no gradients applied in the readout direction during the acquisition of the navigator.
For each phase-encoding step the navigator was then used to recover the phase offset,
which was successively subtracted from the corresponding k-space data in a corresponding echo.
The phases in each echo were adjusted using the timing of each echo-readout,
with respect to the excitation time.
T2* weighted images were first reconstructed taking into account the navigators and then without navigators.
R2* mapping was evaluated assuming a mono-exponential decay of the signal by non-linear fitting of the T2* at the 6 TE,
with and without navigators.