Combined MR quantitative susceptibility mapping and multi-shell diffusion in Parkinson's disease

Area of Science:

• Neuroimaging
• Biomarker Discovery
• Neurodegenerative Diseases

Background:

• Quantitative susceptibility mapping (QSM), neurite orientation dispersion and density imaging (NODDI), and the g-ratio are imaging techniques that have previously shown differences between Parkinson's disease (PD) and healthy individuals.
• The g-ratio has not been previously investigated in the substantia nigra (SN) and putamen regions of PD patients.
• Combining these imaging modalities may offer complementary diagnostic value for PD.

Purpose of the Study:

• To evaluate the diagnostic performance of QSM, NODDI, the g-ratio, and a combined QSM-NODDI marker.
• To assess these markers specifically in the substantia nigra (SN) and putamen of PD patients.

Main Methods:

• A prospective study comparing 15 PD patients and 14 healthy controls.
• Manual segmentation was used to define regions of interest (ROIs) in the SN and putamen.
• Diagnostic performance was quantified using the area under the curve (AUC) of the receiver operating characteristic (ROC) curve.

Main Results:

• Median QSM in the contralateral SN achieved an AUC of 0.77 for PD identification.
• Median isotropic volume fraction from NODDI in the ipsilateral SN showed an AUC of 0.68.
• A combined NODDI-QSM marker demonstrated improved diagnostic performance with an AUC of 0.80.
• No significant differences were observed for the g-ratio between groups.

Conclusions:

• The combination of QSM and NODDI (specifically median QSM and median isotropic volume fraction) enhances the differentiation between PD and healthy controls.
• This combined imaging marker represents a potential biomarker for PD diagnostics.
• These findings support and modestly improve upon previous research combining QSM and NODDI for PD differentiation.