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Hi, The Bayesian framework and Markov Random Field are part of the segmentation method - FAST - which you can read about in: Y. Zhang, M. Brady, and S. Smith. Segmentation of brain MR images through a hidden Markov random field model and the expectation maximization algorithm. IEEE Trans. on Medical Imaging, 20(1):45-57, 2001. this is linked from the "FAST Research Page" which you can find from the FAST online documentation. If you read the SIENA technical report at: http://www.fmrib.ox.ac.uk/analysis/research/siena/siena.pdf then you can see in equation 2 and the discussion afterwards that the true area, A, and volume, V, are not needed, but instead the ratio, f, is found by a calibration process that involves scaling a known image, which then allows the %BVC to be calculated from the edge motion, l, which is defined in equation 1. I hope this helps. All the best, Mark On 21 Jul 2010, at 06:42, Michele Placci wrote: > Dear Prof. Smith, > > thank you for your fast reply. > > For example in your article "Brain atrophy analysis using single and > multiple time point data" in the section > 2.5 change analysis you talk about: bayesian framework and hidden > markov random field. > Can you tell me please where and how do you applied them? > > In the section 2.6 Percentage brain volume change quantification, > you used A (actual brain area) and V (actual brain > volume), but how do you calculated them? > > Thank you in advance. > > > > > 2010/7/21 Stephen Smith <[log in to unmask]> > Hi - there isn't really any "maths" as such that is particularly > interesting I think - SIENA is just a set of heuristic algorithms > tuned for a specific application. Though you might be referring to > a lower-level - for example the maths underneath BET or FAST - in > which case those relevant papers have more information? > > Cheers. > > > > On 21 Jul 2010, at 10:56, Michele Placci wrote: > >> Dear experts, can you tell me please if there is some publications >> that talk about the MATHEMATHICS underlying the calculation of >> volumes, such as adopted by SIENA? >> >> I read the article "Brain atrophy analysis using single and >> multiple time point data" Stephen M. Smith et al >> but I'd like to know more details. >> >> Can you help me please? >> Thank you. > > > --------------------------------------------------------------------------- > Stephen M. Smith, Professor of Biomedical Engineering > Associate Director, Oxford University FMRIB Centre > > FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK > +44 (0) 1865 222726 (fax 222717) > [log in to unmask] http://www.fmrib.ox.ac.uk/~steve > --------------------------------------------------------------------------- > > > >