Robust imaging of hippocampal inner structure at 7T: in vivo acquisition protocol and methodological choices

International audienceOBJECTIVE:Motion-robust multi-slab imaging of hippocampal inner structure in vivo at 7T.MATERIALS AND METHODS:Motion is a crucial issue for ultra-high resolution imaging, such as can be achieved with 7T MRI. An acquisition protocol was designed for imaging hippocampal inner structure at 7T. It relies on a compromise between anatomical details visibility and robustness to motion. In order to reduce acquisition time and motion artifacts, the full slab covering the hippocampus was split into separate slabs with lower acquisition time. A robust registration approach was implemented to combine the acquired slabs within a final 3D-consistent high-resolution slab covering the whole hippocampus. Evaluation was performed on 50 subjects overall, made of three groups of subjects acquired using three acquisition settings; it focused on three issues: visibility of hippocampal inner structure, robustness to motion artifacts and registration procedure performance.RESULTS:Overall, T2-weighted acquisitions with interleaved slabs proved robust. Multi-slab registration yielded high quality datasets in 96 % of the subjects, thus compatible with further analyses of hippocampal inner structure.CONCLUSION:Multi-slab acquisition and registration setting is efficient for reducing acquisition time and consequently motion artifacts for ultra-high resolution imaging of the inner structure of the hippocampus

Understanding dissociations in dyscalculia: A brain imaging study of the impact of number size on the cerebral networks for exact and approximate calculation

Neuropsychological studies have revealed different subtypes of..

Flow structure at: (a) systole (0.25 ≲ <i>t</i>/<i>T</i> ≲ 0.31); (b) cycle-averaged state (0 ≤ <i>t</i>/<i>T</i> ≤ 1); (c) steady state with the Reynolds number at the systolic peak, <i>Re</i> = 651; (d) steady state at <i>Re</i> = 1000.

<p>The velocity iso-surface thresholds are , , , and , respectively.</p

Input flow rate waveform along with the binned input waveform, and the inflow waveform reconstructed from PC-MRI at the inlet of the aneurysm.

<p>The flow rate and pressure waveforms measured upstream of the aneurysm using the ultrasonic flow meter and pressure transducer respectively are shown for comparison.</p

Normalized velocity magnitude () at three selected cut planes in the aneurysm sac.

<p>Each row shows one cardiac phase. Note that for better visibility, every third vector in each direction is shown.</p

PC-MRI parameters.

<p>PC-MRI parameters.</p

A schematic of the experimental setup.

<p>The black solid lines indicate the flow circuit, whereas the red dashed lines indicate the electronics connections. Note that the components are not to scale.</p

Normalized relative pressure, , and normalized velocity magnitude, , at the phantom centerline.

<p>Each blue line represents velocity distribution at the centerline in one phase from diastole (light blue) to systole (dark blue) with the dashed blue line showing the cycle-averaged velocity. The red color coding shows the pressure distribution at the centerline in the same fashion. The centerlines shown at the top right and bottom right are respectively colored by the local systolic velocity and systolic pressure from blue (low) to red (high).</p

L'Avenir de Luchon : journal scientifique, littéraire, annonces et réclames : guide général des baigneurs et des touristes aux eaux thermales, bains de mer de la France et de l'étranger

05 août 18991899/08/05 (N11)-1899/08/05.Appartient à l’ensemble documentaire : MidiPyren