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f_guess = 1 - S/S_
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@quantshah
quantshah committed Jun 15, 2016
1 parent 27bb444 commit f8a89a4
Showing 1 changed file with 1 addition and 1 deletion.
2 changes: 1 addition & 1 deletion dipy/reconst/ivim.py
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Expand Up @@ -278,7 +278,7 @@ def two_stage(data, gtab, x0,
# The guess for f is given by 1 - S0/C, where S0 is the data(b = 0) value

C = data[..., gtab.bvals == split_b][0] - D_guess * split_b
f_guess = data[..., 0] / C
f_guess = 1.0 - data[..., 0] / C

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@etpeterson

etpeterson Jun 16, 2016

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I think you need to have it 1-C/data[...,0] because C (intercept of the diffusion only) is < data[...,0](intercept of the perfusion+diffusion).

Also, does the normal DTI fit not potentially return an intercept? The way you're calculating C seems a little fishy although maybe that's because I haven't digested it fully yet.

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@arokem

arokem Jun 16, 2016

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The DTI fit will return an intercept once #1036 gets merged. For the time being, the equation to calculate the intercept from a DTI model is in that PR.
x0[..., 1] = f_guess

return one_stage(data, gtab, x0, jac, bounds, tol, routine, algorithm,
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