[The effect of aging on the apparent diffusion coefficient of normal appearing white and gray matter]

To test if the apparent diffusion coefficient (ADC) values reflect the ultrastructural changes of normal appearing white and gray matter with advancing age.

We selected 45 patients with normal MRI and DW imaging findings. DW and MRI imaging was performed and for each patient the average ADC on trace images of the frontal and occipital white matter and the thalamus were compared with increasing patient age.

The average ADC value was 0.753+/-0.054 x 10-3 mm2/sec in frontal white matter, 0.673+/-0.085 x 10-3 mm2/sec in occipital white matter, and 0.763+/-0.063 x 10-3 mm2/sec in the thalamus. For white matter, ADC values increased with advancing age. Although ADC tended to increase with age, comparison of individual thalamic ADC and patient ages did not reach statistical significance.

Advancing age is associated with a small but statistically significant increase of water diffusibility in human white matter. This increase may reflect mild structural changes with normal aging.