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FIX: Resolve numeric overflow in drift estimation node #1324

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Aug 19, 2024
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FIX: Resolve numeric overflow in drift estimation node #1324

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13 changes: 10 additions & 3 deletions mriqc/interfaces/diffusion.py
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Original file line number Diff line number Diff line change
Expand Up @@ -662,10 +662,17 @@ def _run_interface(self, runtime):
self.inputs.full_epi, suffix='_nodriftfull', newpath=runtime.cwd
)
full_img = nb.load(self.inputs.full_epi)

# Read slope and intercept (see #1315)
slope, intercept = full_img.header.get_slope_inter()
slope = slope if slope is not None else 1.0
intercept = intercept if intercept is not None else 0.0
corrected = (
full_img.get_fdata() * fitted[np.newaxis, np.newaxis, np.newaxis, :] / slope
- intercept
)
full_img.__class__(
(full_img.get_fdata() * fitted[np.newaxis, np.newaxis, np.newaxis, :]).astype(
full_img.header.get_data_dtype()
),
corrected.astype(full_img.header.get_data_dtype()),
full_img.affine,
full_img.header,
).to_filename(self._results['out_full_file'])
Comment on lines +665 to 678
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@effigies effigies Aug 19, 2024 •
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Sorry for the delay. No, you just want:

full_img.__class__(
    full_img.get_fdata() * fitted[np.newaxis, np.newaxis, np.newaxis, :],
    full_img.affine
    full_img.header
).to_filename(self._results['out_full_file'])

You pretty much never want to dynamically coerce the type. All of nibabel's machinery assumes that the data is valid and that the header encodes the intent, and will perform scaling on your behalf if continuous data needs to be discretized into an integer dtype.

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I assume that applies the slope and intercept when generating the spatialimage object, correct?

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Yes, it will calculate a new slope and intercept based on the min/max values of the data array.

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