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

Accurate and automated methods for measuring the thickness of human cerebra l cortex could provide powerful tools for diagnosing and studying a variety of neurodegenerative and psychiatric disorders. Manual methods for estimat ing cortical thickness from neuroimaging data are labor intensive, requirin g several days of effort by a trained anatomist. Furthermore, the highly fo lded 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 be en impractical to obtain accurate thickness estimates for the entire cortex in individual subjects, or group statistics for patient or control populat ions. Here. we present an automated method for accurately measuring the thi ckness of the cerebral cortex across the entire brain and for generating cr oss-subject statistics in a coordinate system based on cortical anatomy. Th e 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 pop ulations or even individual subjects. The reliability and accuracy of this new method are assessed by within-subject test-retest studies, as well as b y comparison of cross-subject regional thickness measures with published va lues.