[Neuroimaging] [DIPY] weird DKI maps

[Ping-Hong Yeh]

Hi DIPY users,

Would you comment what could go wrong for DKI fitting of this mean kurtosis
(MK) map using a three-shell DWI (b=3000,2000,1000)?
The values of MK map are all zero except those in the sulci and ventricles.

Here is the command I used,
fwhm = 1.25
gauss_std = fwhm / np.sqrt(8 * np.log(2))  # converting fwhm to Gaussian std
data_smooth = np.zeros(data.shape)
for v in range(data.shape[-1]):
    data_smooth[..., v] = gaussian_filter(data[..., v], sigma=gauss_std)


dkimodel = dki.DiffusionKurtosisModel(gtab)
dkifit = dkimodel.fit(data_smooth, mask=mask)
MK = dkifit.mk(0, 3)
AK = dkifit.ak(0, 3)
RK = dkifit.rk(0, 3)

I have been using the same scripts for other 200ish data and the DKI maps
were just fine.

Thank you.

Ping
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