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Hi, The scaling derived by SIENAX is based on an affine registration to the standard space that takes into account the skull estimates provided by BET. I would also not expect to see a strong correlation between this and age, but it is possible that the estimate of the skull is not very accurate, especially if there is strong atrophy or unusual dura. If you run it with the debug option and look at the _brain_skull images then it might give you an indication of whether there are any problems. Note that the skull estimate is always noisy though, and it would only be a problem if there were large areas that were coherently and incorrectly classified. All the best, Mark On 7 Sep 2010, at 21:00, Forrest Johnson wrote: > Hello FSL Experts, > > I have used SIENA (sienax <T1_image> -o <output_name> -B 88 85 149) > to capture ICV in several subjects and have found an unexpected > relationship between age and ICV (a strong inverse relationship with > ICV decreasing as age increases). I typically would not expect to > observe such a relationship (unless my older subjects have smaller > heads), so I was wondering if my methodology was correct (sienax > <T1_image> -o <output_name> -B 88 85 149)? A more likely scenario > might be a decrease in brain volume with age, but I was under the > impression that when I multiplied the total brain volume by the > VSCALING factor, that I was capturing ICV. Is this correct? > > Some of the captured ICV values are listed below. > > Cheers! > > ICV Age > 1519642.91 62.92 > 1372345.71 69.83 > 1566289.91 61.08 > 1381052.66 68.33 > 1498448.09 58.83 > 1437447.51 67 > 1500638.8 69.33 > 1413323.2 76.08 > 1668326.34 61.42 > 1626539.29 65.25 > 1520028.79 68.83 > 1439787.42 77.42 > 1367213.24 75.5 > 1462530.25 76.83 > 1392069.23 82.25 > 1391631.46 83.5 >