Measuring the thickness of the human cerebral cortex from magnetic resonance images

TLDR

Accurate, automated cortical thickness measurement is needed because manual estimation is labor‑intensive, error‑prone in highly folded regions, and impractical for whole‑brain or group analyses. The authors introduce an automated technique that measures cortical thickness across the entire brain and produces cross‑subject statistics in a cortical‑anatomy–based coordinate system. Reliability and accuracy were evaluated through within‑subject test–retest studies and by comparing regional thickness values with published benchmarks. The method achieves an intersubject standard deviation of less than 0.5 mm, allowing detection of focal atrophy in small populations or individual subjects.

Abstract

Accurate and automated methods for measuring the thickness of human cerebral cortex could provide powerful tools for diagnosing and studying a variety of neurodegenerative and psychiatric disorders. Manual methods for estimating cortical thickness from neuroimaging data are labor intensive, requiring several days of effort by a trained anatomist. Furthermore, the highly folded nature of the cortex is problematic for manual techniques, frequently resulting in measurement errors in regions in which the cortical surface is not perpendicular to any of the cardinal axes. As a consequence, it has been impractical to obtain accurate thickness estimates for the entire cortex in individual subjects, or group statistics for patient or control populations. Here, we present an automated method for accurately measuring the thickness of the cerebral cortex across the entire brain and for generating cross-subject statistics in a coordinate system based on cortical anatomy. The intersubject standard deviation of the thickness measures is shown to be less than 0.5 mm, implying the ability to detect focal atrophy in small populations or even individual subjects. The reliability and accuracy of this new method are assessed by within-subject test–retest studies, as well as by comparison of cross-subject regional thickness measures with published values.