Are intra-cellular volume fraction, intra-neurite volume fraction, and neurite density index the same thing?

[Tigris Joseph]

Hello,

Are intra-cellular volume fraction, intra-neurite volume fraction, and neurite density index different names for the same metric?

Tigris

[Gary]

Hi Tigers,

That is correct.  Intra-cellular volume fraction was used in my original NODDI paper, which followed the standard terminology of the field at the time.  Later on, in our subsequent Bingham-NODDI paper, we renamed the term to be intra-neurite volume fraction, which more accurately describes what we are modelling.  In particular, soma, the cell body, is intra-cellular but is included in the extra-cellular space.  The terms intra-neurite and extra-neurite now characterise how we model neuronal tissue more accurately.  About the same time, we coined the term neurite density index (NDI) that can be used interchangeably with intra-neurite volume fraction, which can be a mouth full to say.

Thanks a lot asking the question!

[Gary]

Oops.  Just noticed that auto-correct just caught me out.  Sorry Tigris!