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IqsmEchoWeighting

qsm_core::inversion::iqsm_echo_weighting

Enum IqsmEchoWeighting 

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pub enum IqsmEchoWeighting {
    MagnitudeTeSquared,
    MagnitudeSquaredTeSquared,
}
Expand description

How the multi-echo iQSM and iQFM entry points combine their per-echo reconstructions: Σ w·χ / Σ w over the echoes, voxel by voxel, with the weight w below. Without magnitudes both are TE² (uniform magnitude), as in both of the authors’ implementations.

The authors’ two implementations disagree (checked at sunhongfu/iQSM 81f5462 and sunhongfu/iQSM_Plus 3ba25f5):

  • MATLAB (published with the paper): sunhongfu/iQSM legacy/matlab/demo_multi_echo.m:152-160 and sunhongfu/iQSM_Plus legacy/matlab/iQSM.m:260-267 / iQFM.m:263-270 multiply each echo’s output by its TE and fit that against TE with echofit.m (sunhongfu/iQSM legacy/matlab/iQSM_fcns/echofit.m, zero intercept): Σ mag·TE·(TE·χ) / Σ mag·TE², i.e. weights mag·TE².
  • Python (the current drivers): sunhongfu/iQSM run.py:170 and app.py:416 weight by (mag·TE)², i.e. magnitude squared, although they print “Magnitude × TE²”. QSM-CI’s iQSM and iQFM originals (bb163ef) run this Python.

The default is MagnitudeSquaredTeSquared, (mag·TE)² (Ashley’s decision, 2026-10-31). Each echo’s χ (or local field) estimate is its phase divided by TE, and the phase noise has standard deviation ∝ 1/mag, so the estimate’s noise variance is ∝ 1/(mag·TE)²: (mag·TE)² is the inverse-variance weight, which gives the combination of least variance. It is also the authors’ current Python, and iQSM+‘s weighting in both of its authors’ implementations (sunhongfu/iQSM_Plus legacy/matlab/iQSM_plus.m:273-275, run.py:199; see iqsm_plus_multi_echo, which has no choice). The MATLAB’s mag·TE² (MagnitudeTeSquared) stays as an option, for parity with the implementation published with the paper.

Variants§

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MagnitudeTeSquared

w = mag·TE²: the authors’ MATLAB echo fit (an option, for parity with it).

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MagnitudeSquaredTeSquared

w = (mag·TE)² = mag²·TE²: inverse-variance; the authors’ Python drivers (the default).

Implementations§

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impl IqsmEchoWeighting

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pub fn weight(self, mag: f64, te: f64) -> f64

The weight of one echo with magnitude mag and echo time te.

Trait Implementations§

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impl Clone for IqsmEchoWeighting

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fn clone(&self) -> IqsmEchoWeighting

Returns a duplicate of the value. Read more
1.0.0 (const: unstable) · Source§

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Copy for IqsmEchoWeighting

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impl Debug for IqsmEchoWeighting

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl Default for IqsmEchoWeighting

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fn default() -> IqsmEchoWeighting

Returns the “default value” for a type. Read more
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impl Eq for IqsmEchoWeighting

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impl PartialEq for IqsmEchoWeighting

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fn eq(&self, other: &IqsmEchoWeighting) -> bool

Equality operator ==. Read more
1.0.0 (const: unstable) · Source§

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=. Read more
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impl StructuralPartialEq for IqsmEchoWeighting

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