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P1‐226: Deformation morphometry reveals longitudinal atrophy related to cognitive decline and APOE‐e4 status
Author(s) -
Cardenas Valerie A.,
Chao Linda L.,
Studholme Colin,
Schuff Norbert,
Weiner Michael W.
Publication year - 2008
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2008.05.815
Subject(s) - atrophy , entorhinal cortex , cognitive decline , psychology , corpus callosum , cognition , audiology , dementia , cortex (anatomy) , hippocampus , neuroscience , medicine , disease
pocampal (HIP), and lateral-ventricle (LV) volumes in patients with AD is an important goal. Accuracy can be affected, however, by local-volume changes related to MRI-scanner-gradient nonlinearities and inconsistent positioning of subjects within the scanner (particularly along the Z-axis). Furthermore, standard canthomeatal (CM) alignment results in the cerebrum being centered several cms away from isocenter. Objective: To quantify the effect of Z-shifts into, and out of, the scanner on WBT, HIP, and LV volumes. Methods: High resolution, volumetric T1-weighted MRI data were acquired in 9 normal adults on a Siemens Sonata Vision 1.5T scanner: first, with CM-alignment, and then with the scanner bed moved 50-mm out of the magnet. A gradient-distortion correction field (GDCF) was generated using spherical harmonic expansion to map coordinates from an “ideal” coordinate system (a Lego-DUPLO® phantom) to the imaging coordinate system of the scanner. FreeSurfer v4.0.1 was used to automatically classify voxels in each MRI dataset as WBT, HIP, and LV. The effect of Z-shift on tissue volume was simulated in 4-mm steps from -50-mm to 50-mm by applying the GDCF to each of the FreeSurfer tissuemasks, z-shifting these masks, applying the inverse-GDCF, shifting the resulting masks back, and calculating the resulting volumes by integrating the intensities. Results: Simulated 50-mm Z-shifts into, and out of, the magnet had asymmetric effects on both mean WBT-volumes [out: 18.8-cc decrease (-1.5%), p 0.02; in: 98.8-cc decrease (-7.4%), p 0.0001) and mean LVvolumes [out: 0.1-cc decrease (-0.8%), p 0.16; in: 1.3-cc decrease (-8.2%), p 0.0001); they had symmetric effects on mean HIP-volumes [out: 0.5-cc decrease (-5.2%), p 0.0001; in: 0.4-cc decrease (-4.0%), p 0.0001). Volumes obtained from the actual 50-mm-out Z-shifts were highly correlated with those from the simulated 50-mm-out Z-shifts (WBT: r 0.996, p 0.0001; HIP: r 0.905, p 0.0008; LV: r 0.999, p 0.0001).