Age-related changes in conventional, magnetization transfer, and diffusion-tensor MR imaging findings: study with whole-brain tissue histogram analysis.
OBJECTIVE
To investigate the influence of aging on conventional magnetic resonance (MR) imaging-, magnetization transfer MR imaging-, and diffusion-tensor MR imaging-derived measurements.


METHODS
Dual-echo T1-weighted magnetization transfer and diffusion-tensor MR images of the brain were obtained in 89 healthy subjects. Normalized brain parenchymal volume (NBV) was measured by using a fully automated technique. Magnetization transfer ratio (MTR), apparent diffusion coefficient (ADC), and fractional anisotropy (FA) histograms were created for the whole brain (MTR values) or for a large representative portion of it (ADC and FA values). Bivariate correlations were assessed by using the Spearman rank correlation coefficient. A stepwise selection procedure was used to identify the combination of variables that were most influenced by subject age in a multivariate regression model.


RESULTS
Significant correlations were found between subject age and the following variables: number of hyperintense areas in the brain at T2-weighted MR imaging (r = 0.63, P <.001), NBV (r = -0.79, P <.001), mean ADC (r = 0.34, P =.001), ADC peak height (r = -0.34, P =.001), and FA peak height (r = -0.57, P <.001). NBV correlated significantly with number of hyperintense areas (P <.001), MTR peak height (P <.001), mean ADC (P =.001), ADC peak height (P =.001), and FA peak height (P <.001). The final multivariable regression model included NBV and number of hyperintense areas at T2-weighted MR imaging as independent predictors of subject age.


CONCLUSIONS
In addition to the extent of T2-weighted MR imaging hyperintense areas and the measurement of NBV, diffusion-tensor MR imaging provides additional in vivo information about microstructural age-related brain tissue changes.
Rovaris
Marco
M
Neuroimaging Research Unit, Department of Neuroscience, Scientific Institute and University Ospedale San Raffaele, Via Olgettina 60, 20132 Milan, Italy.
Iannucci
Giuseppe
G
Cercignani
Mara
M
Sormani
Maria Pia
MP
De Stefano
Nicola
N
Gerevini
Simonetta
S
Comi
Giancarlo
G
Filippi
Massimo
M
D000328:Adult; D000375:Aging / Q000502:physiology*; D001921:Brain / Q000033:anatomy & histology*; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D012044:Regression Analysis