MR volume segmentation of gray matter and white matter using manual thresholding: dependence on image brightness

Abstract

Purpose: To describe a quantitative MR imaging segmentation method for determination of the volume of cerebrospinal fluid, gray matter, and white matter in living human brain, and to determine the method's reliability.

Methods: We developed a computer method that allows rapid, user-friendly determination of cerebrospinal fluid, gray matter, and white matter volumes in a reliable manner, both globally and regionally. This method was applied to a large control population (N = 57).

Results: Initially, image brightness had a strong correlation with the gray-white ratio (r = .78). Bright images tended to overestimate, dim images to underestimate gray matter volumes. This artifact was corrected for by offsetting each image to an approximately equal brightness. After brightness correction, gray-white ratio was correlated with age (r = -.35). The age-dependent gray-white ratio was similar to that for the same age range in a prior neuropathology report. Interrater reliability was high (.93 intraclass correlation coefficient).

Conclusions: The method described here for gray matter, white matter, and cerebrospinal fluid volume calculation is reliable and valid. A correction method for an artifact related to image brightness was developed.