Accuracy and validity of stereology as a quantitative method for assessment of human temporal lobe volumes acquired by magnetic resonance imaging

The object of this study was to compare the accuracy and validity of stereo logy as a method for determining whole temporal lobe volume with the more e stablished technique of semi-automated thresholding acid tracing. Ten, fixe d, post-mortem human brains, were imaged using a three dimensional (3D) acq uisition protocol. The volume of the left temporal lobe, dissected from eac h brain, was determined by fluid displacement. Each volume was compared to measurements obtained from magnetic resonance images (MRI) of the post-mort em brain using each of the two segmentation methods. Post-acquisition proce ssing was performed using MEASURE software. Three investigators performed e ach measurement three times using each method, yielding a total of 180 meas urements. Stereology took, on average, half the time of thresholding/tracin g. Using a clinically acceptable variation for 95% of repeat measures; both intra-observer and inter-observer variation were acceptable for each techn ique. However, validity, as demonstrated by graphs of agreement against wat er displacement showed that the "limits of agreement" using stereology were within the acceptable range, while those using the thresholding/tracing te chnique were not. Quantitative estimates of variation and a graphical repre sentation of the limits of agreement show that stereology is at least as pr ecise as the thresholding/tracing method but is superior in terms of speed and validity. This has broad implications for published estimates of brain region volumes in human diseases such as epilepsy, dementia and other neuro degenerative disorders. (C) 2000 Elsevier Science Inc. All rights reserved.