Zg. Chen et al., Diffusion tensor trace mapping in normal adult brain using single-shot epitechnique - A methodological study of the aging brain, ACT RADIOL, 42(5), 2001, pp. 447-458
Purpose: To quantify age-related changes of the average diffusion coefficie
nt value in normal adult brain using orientation-independent diffusion tens
or trace mapping and to address the methodological influences on diffusion
quantification.
Material and Methods: Fifty-four normal subjects (aged 20-79 years) were st
udied on a 1.5-T whole-body MR medical unit using a diffusion-weighted sing
le-shot echo-planar imaging technique. Orientation-independent diffusion te
nsor trace maps were constructed for each subject using diffusion-weighted
MR measurements in four different directions using a tetrahedral gradient c
ombination pattern. The global average (including cerebral spinal fluid) an
d the tissue average of diffusion coefficients in adult brains were determi
ned by analyzing the diffusion coefficient distribution histogram for the e
ntire brain. Methodological influences on the measured diffusion coefficien
t were also investigated by comparing the results obtained using different
experimental settings.
Results: Both global and tissue averages of the diffusion coefficient are s
ignificantly correlated with age (p<0.03). The global average of the diffus
ion coefficient increases 3% per decade after the age of 40, whereas the in
crease in the tissue average of diffusion coefficient is about 1% per decad
e. Experimental settings for self-diffusion measurements, such as data acqu
isition methods and number of b-values, can slightly influence the statisti
cal distribution histogram of the diffusion tensor trace and its average va
lue.
Conclusion: Increased average diffusion coefficient in adult brains with ag
ing are consistent with findings regarding structural changes in the brain
that have been associated with aging. The study also demonstrates that it i
s desirable to use the same experimental parameters for diffusion coefficie
nt quantification when comparing between different subjects and groups of i
nterest.