[vtkusers] How to calculate isosurface value for MR volume data set?

[S, Maheshanand (MED, Contractor)]

Hi groups..
while using vtkContourFilter in the example Medical3.cxx,we set the value as 500 for skin and 1150 for bone.
How to set this value?
Is there is any standard value available for MR volume dataset?
Since in MRI we are interested to extract softtissues rather than bones,so isosurface value for softtissues is approximately what?
Looking for ur valuable suggestion.
Thanx in advance.

rgds,
mahesh.