A population‐specific symmetric phase model to automatically analyze susceptibility‐weighted imaging (SWI) phase shifts and phase symmetry in the human brain

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 T₁‐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. J. Magn. Reson. Imaging 2010;31:215–220. © 2009 Wiley‐Liss, Inc.