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Age-Dependent Normal Values of T2* and T2′ in Brain Parenchyma

S. Siemonsena et al, 

Published online before print February 13, 2008, doi: 10.3174/ajnr.A0951

AJNR May 2008 29: 950-955

Decrease in T2′ and T2* values in GM and increase of T2* values in WM correlate with the progress of brain aging. Explanations for decreasing T2′ and T2* values include iron deposition in the caudate and lentiform nucleus. In contrast to T2* values, there is no association of T2′ values with the degree of leukoaraiosis. These age-dependent values can be used as a reference in neurovascular diseases and for the discussion of functional MR imaging data.

Both cortical and subcortical grey matter, and white matter generally speaking decrease with aging.

However, there are several aspects to that bring some nuances to this conclusion. First, it is well known that cortical grey matter does not decrease a) linearly, and b) differs in speed and onset per brain area. I believe something similar is the case for white matter, where the decline has been suggested to follow an anterior-posterior gradient.

Second, a lot depends on what you intend measure. So for grey matter you can look at both density and volume (like cortical thickness). For white matter you can look at FA values, RD values, myelin water fraction, ..... etc. A crucial question is: are all these values telling the same story of age related decline? I'm not sure.

So, if by 'forensic age estimation' you mean determining the age of an individual by means of the measures discussed above, I believe it's too early for that. Nonetheless, different measures may be used at some point as converging evidence for a particular age.

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