Robust automatic segmentation and characterization of lateral ventricle size in the ADNI cohort

Abstract

Lateral ventricle size is often used to quantify brain atrophy in aging and in neurodegenerative diseases. Our goal was to apply a recently developed, automatic segmentation procedure to characterize lateral ventricle volumes in subjects from NC, MCI and AD groups from the Alzheimer's Disease Neuroimaging Initiative (ADNI). T1w MRI data (100 NC, 200 MCI, 100 AD) were randomly selected from the baseline scans of the ADNI database. MRI data were corrected for image intensity non-uniformity [Sled, Trans Med Imag 1998;17:87-97], stereotaxically transformed [Collins, J Comput Assist Tomog 1994;18:192-205] and resampled onto a 1mm3 grid. Fusion based ventricle segmentation [Fonov, ISMRM 2010] was used to automatically segment the lateral ventricles and estimate their volume. The method performs non-linear registration to a minimum-deformation template derived from a separate cohort of AD subjects, and searches through a library of manually segmented labels from that cohort The segmentations of the ‘n’ closest samples are combined with label fusion algorithm to complete the segmentation of the lateral ventricles for given subject. Results from a separate study shows very high accuracy to manual segmentation results (kappa = 0.962) [Fonov, ISMRM 2010]. An ANOVA shows significant between-group differences (p < 0.0022) for native (absolute) lateral ventricle volumes. NC lateral ventricles were smaller ([mean(sd)cc^3] 45.0(27.5)) than MCI (56.7(30.1)) and AD (59.3(29.3)); however there was no statistically significant difference in volume between MCI and AD groups. When normalized by intracranial volume, there was a significant difference (p = 0.048) in normalized lateral ventricle size at baseline for MCI subjects that converted to AD during the follow-up period, compared with those that did not convert. On average, converters' lateral ventricles were 17.3% larger than non-converters. In this subset, lateral ventricle volume does not appear change significantly between MCI and AD groups. However, MCI subjects with larger ventricles have a higher probability of conversion to AD.