Retrospective study showing that standard SMwI outperforms SWI- and neuromelanin-derived reconstructions for differentiating early Parkinson’s disease from controls by clinical diagnosis, though SWI-driven SMwI approaches standard SMwI when PET is used as the reference.

Offers a practical fallback imaging biomarker for detecting nigral changes and improving patient selection/stratification in trials when dedicated SMwI is unavailable, but provides limited direct insight into disease mechanisms or therapeutic targets.

BACKGROUND: Susceptibility map-weighted imaging (SMwI) provides high accuracy for early Parkinson's disease (ePD) by enhancing nigral hyperintensity. However, standard SMwI requires dedicated acquisition; reconstruction from routinely acquired sequences may offer a practical alternative. PURPOSE: To compare the diagnostic performance of standard SMwI with SWI- and neuromelanin (NM)-driven SMwI for differentiating ePD from disease controls (DC). STUDY TYPE: Retrospective. SUBJECTS: One hundred and eighty-seven drug-naïve ePD (age: 67.5 ± 9.4 years, 102 male) and 43 DC (age: 67.1 ± 9.2 years, 12 male). FIELD STRENGTH/SEQUENCE: 3 T, multi-echo gradient-echo (GRE) for standard SMwI; GRE-based NM imaging: multi-echo GRE for SWI. ASSESSMENT: Nigral hyperintensity was assessed by three neuroradiologists (4-, 2-, and 1-year experience). Diagnostic performance was evaluated using clinical diagnosis for all subjects and PET for 106 subjects (98 ePD, 8 DC). PET-based assessment included side-based analyses accounting for PET laterality and patient-based analyses regardless of direction. STATISTICAL TESTS: Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy and area under the curve (AUC) were assessed using clinical diagnosis as reference; sensitivity, specificity, and accuracy using PET. Significance was set at p < 0.05. RESULTS: Using clinical diagnosis as reference, standard SMwI showed highest diagnostic performance (sensitivity 0.856; specificity 1.000; PPV 1.000; AUC 0.928). SWI-driven SMwI maintained similar sensitivity (p = 0.355) but showed significantly reduced specificity, PPV, accuracy, AUC. In the PET subgroup, side- and patient-based analyses showed no differences in sensitivity (p = 0.261, p = 0.670), specificity (p = 1.000, p = 1.000) and accuracy (p = 0.268, p = 0.695) between standard and SWI-driven SMwI. DATA CONCLUSION: SWI-driven SMwI approached the diagnostic performance of standard SMwI with PET reference but showed inferior performance with clinical diagnosis, suggesting a fallback option when dedicated SMwI is unavailable. EVIDENCE LEVEL: 3. TECHNICAL EFFICACY: Stage 1.