Isovoxel-Based Morphology of Hippocampi and Amygdalae: A Comparison of Manual and Automated Volume Measurements

Abstract

This study evaluated the correlation between manual and automated morphometric measurements of hippocampi and amygdalae. Twenty-three patients with no history of seizures and normal electroencephalograms were examined with a standardized MRI protocol that included isovoxel volumetric acquisitions of the brain. Images were evaluated in axial-oblique plane to trace manually the grey matter contours of hippocampi and amygdalae obtaining their volumes. They were also processed automatically carrying out segmentation and sub segmentation aligning images (AC-PC) and standardizing them into Talairach space to obtain then comparable grey matter volumes. Tabled results were age, gender and volumes of each side from both, manual and automated measurements. Forward stepwise multiple regression analyses were carried out considering sex and age as independent and hippocampi-amygdalae as dependent variables. Linear regression analyses were then carried out considering for the total of cerebral hemispheres each manual measurement as independent and automatically obtained volumes as dependent variables. In the multiple regression analyses the following values were obtained: age-gender vs. manual measurements showed r=0.83; r²=0.69; _adjustedr²=0.64; F(3,19)=14.36 while age-gender vs. automated values showed r=0.86; r²=0.74; _adjustedr²=0.70; F(3,19)=18.81. Linear regression between manual and automated measurements for all hemispheres showed for hippocampus: r=0.97; r²=0.95; F(1,44)=896.59. For amygdala results were: r=0.94; r²=0.89; F(1,44)=391.11. The results of these analyses suggest that both manual and automated procedures of measurement are highly consistent. A regression between age and volumes of both hippocampus and amygdala was also noted.