Complex-Valued Voxel Thresholding Increases Image Contrast in SWI

Daniel B. Rowe¹, E. Mark Haacke²

It is often desirable to threshold signal plus noise voxels from pure noise voxels. Generally thresholding utilizes only the magnitude of the images. More recently a method has used both the magnitude and phase. This work is an extension and uses the normality of the real and imaginary values with phase coupled means. A statistic is derived that is F-distributed in large samples. In small samples Monte-Carlo critical values can be used. We apply this method to SWI images and show increased image contrast while it is found to be more robust to phase variations from unwanted field inhomogeneity effects.