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IC‐P‐019: Automated quantification of hippocampal asymmetry in MRI in semantic dementia and Alzheimer's disease
Author(s) -
Leung Kelvin,
Mahoney Colin,
Barnes Josephine,
Ourselin Sebastien,
Fox Nick
Publication year - 2011
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.2011.05.036
Subject(s) - dementia , hippocampal formation , temporal lobe , atrophy , psychology , magnetic resonance imaging , cognitive impairment , segmentation , alzheimer's disease , nuclear medicine , medicine , neuroscience , cardiology , cognition , artificial intelligence , radiology , computer science , disease , epilepsy
Background: Alzheimer’s disease (AD) is typically presented with progressive cognitive impairment and symmetrical global cerebral atrophywith early symmetrical hippocampal loss. Semantic dementia (SD) is characterisedby semantic memory impairment with focal, and often asymmetrical, anterior hippocampaland temporal lobe atrophy (greater left-sided atrophy). Asymmetry in the hippocampusmay help to distinguish SD from AD. We applied an automated technique toquantify hippocampal asymmetry from a single MR scan using the boundary shiftintegral (BSI) Methods: Volumetric T1-weighted MR scans were acquired on 10 clinically diagnosed AD and 10 SD patients, and 10 age-matched controls. The hippocampi were first segmented using an automated hippocampal segmentation method based on multiple-atlas propagation and segmentation (MAPS). In order to allow the direct comparison of the left and right hippocampi, we generated a mirror image by flipping each subject image left and right.We calculated the left hippocampal BSI (HBSI) using the left hippocampi of the unflipped and flipped images, and the right HBSI in a similar way. We defined the “absolute hippocampal asymmetry” as the absolute value of average HBSI divided by average volume of the left and right hippocampi. We also calculated the volume ratio between the left and right hippocampi (denoted as "L/R ratio"). For validation and normative purposes, we applied our methods to the baseline volumetric T1-weightedMR scans of 682 subjects (200 controls, 338 MCI and 144 AD) downloaded from the ADNI website (www. adni-info.org).Results: L/R ratios of AD, MCI and controls from both datasets were very close to 1 (Table 1). SD subjects however had a lower L/R ratio and higher absolute hippocampal asymmetry than AD and controls (p1⁄40.01, all tests) (Table 2, and Figures 1 and 2).Conclusions:Our results show that we can automatically quantify the asymmetry in the hippocampus and that our methods may provide useful information for the differential diagnosis of SD and AD.