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Automated unwrapping of MR phase images applied to BOLD MR-venography at 3 Tesla
Alexander Rauscher1, Markus Barth, Jürgen R Reichenbach
1NMR Group, Institute of Medical Physics, University of Vienna, Austria.
Purpose:
To improve the diagnostic value of BOLD MR-Venography by removing artifacts related to phase wrapping, particularly in regions of large background susceptibilities at high magnetic field strengths.
Materials And Methods:
High resolution, T(2)(*)-weighted, single echo images were acquired on a 3 T system (Medspec 30/80 Avance, Bruker Medical, Ettlingen, Germany) with a three-dimensional, first order velocity compensated gradient echo sequence using a quadrature transmit/receive birdcage head coil. Data of nine healthy subjects and 19 patients were evaluated (age range: 27 to 76 years). To achieve improved MR-venograms, a fully automated region-growing phase unwrapping algorithm and subsequent high pass filtering were applied to phase images prior to the computation of minimum intensity projections.
Results:
Considerably improved visualization of venous structures in regions of large background susceptibility-induced field inhomogeneities is demonstrated in healthy subjects and patients with brain tumors.
Conclusion:
BOLD MR venograms are improved compared to previous post-processing algorithms. It is now feasible to obtain high-resolution images also in inhomogeneous regions, which increases the clinical potential of BOLD MR-Venography.
