Purpose: To create a population-specific symmetric phase model and to evaluate the susceptibility-weighted imaging (SWI) phase in terms of phase shift using different segmentation methods (manual and automatic) and phase shift symmetry, which is expected as a marker for lateralized Parkinson's disease (PD) symptoms.
Materials and methods: SWI and T(1)-weighted data from 25 PD patients and five healthy controls were acquired on a 3T MRI system. A population-specific, symmetric phase model was developed. Regions of interest (ROIs) were defined manually on the phase model, manually on each individual data set, and automatically using model-based segmentation (MBS). Manually- and MBS-defined ROIs were compared using kappa values, and left-right phase symmetry was evaluated using correlation analysis.
Results: Independent of the analysis method, a phase increase from the anterior to the posterior putamen, and the average phase value relationship substantia nigra > globus pallidus > red nucleus was found. Phase symmetry analysis shows a difference between lateralized and symmetric PD.
Conclusion: The symmetric phase model helps to analyze phase data with similar accuracy, but a greatly reduced tracing effort compared to individual tracing and also allows evaluating left-right phase symmetries.
(c) 2009 Wiley-Liss, Inc.