Quantitative assessment of susceptibility-weighted imaging processing methods

Purpose: To evaluate different susceptibility-weighted imaging (SWI) phase processing methods and parameter selection, thereby improving understanding of potential artifacts, as well as facilitating choice of methodology in clinical settings.

Materials and Methods: Two major phase processing methods, homodyne-filtering and phase unwrapping-high pass (HP) filtering, were investigated with various phase unwrapping approaches, filter sizes, and filter types. Magnitude and phase images were acquired from a healthy subject and brain injury patients on a 3T clinical Siemens MRI system. The results were evaluated based on image contrast-to-noise ratio and presence of processing artifacts.

Results: When using a relatively small filter size (32 pixels for the matrix size 512 × 512 pixels), all homodynefiltering methods were subject to phase errors leading to 2% to 3% masked brain area in lower and middle axial slices. All phase unwrapping-filtering/smoothing approaches demonstrated fewer phase errors and artifacts compared to the homodyne-filtering approaches. For performing phase unwrapping, Fourier-based methods, although less accurate, were 2-4 orders of magnitude faster than the PRELUDE, Goldstein, and Quality-guide methods.

Conclusion: Although homodyne-filtering approaches are faster and more straightforward, phase unwrapping followed by HP filtering approaches perform more accurately in a wider variety of acquisition scenarios.