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http://dx.doi.org/10.13104/jksmrm.2013.17.4.275

Gaussian Filtering Effects on Brain Tissue-masked Susceptibility Weighted Images to Optimize Voxel-based Analysis  

Hwang, Eo-Jin (Department of Radiology, Kyung Hee University Hospital at Gangdong, College of Medicine, Kyung Hee University)
Kim, Min-Ji (Department of Radiology, Kyung Hee University Hospital at Gangdong, College of Medicine, Kyung Hee University)
Jahng, Geon-Ho (Department of Radiology, Kyung Hee University Hospital at Gangdong, College of Medicine, Kyung Hee University)
Publication Information
Investigative Magnetic Resonance Imaging / v.17, no.4, 2013 , pp. 275-285 More about this Journal
Abstract
Purpose : The objective of this study was to investigate effects of different smoothing kernel sizes on brain tissue-masked susceptibility-weighted images (SWI) obtained from normal elderly subjects using voxel-based analyses. Materials and Methods: Twenty healthy human volunteers (mean $age{\pm}SD$ = $67.8{\pm}6.09$ years, 14 females and 6 males) were studied after informed consent. A fully first-order flow-compensated three-dimensional (3D) gradient-echo sequence ran to obtain axial magnitude and phase images to generate SWI data. In addition, sagittal 3D T1-weighted images were acquired with the magnetization-prepared rapid acquisition of gradient-echo sequence for brain tissue segmentation and imaging registration. Both paramagnetically (PSWI) and diamagnetically (NSWI) phase-masked SWI data were obtained with masking out non-brain tissues. Finally, both tissue-masked PSWI and NSWI data were smoothed using different smoothing kernel sizes that were isotropic 0, 2, 4, and 8 mm Gaussian kernels. The voxel-based comparisons were performed using a paired t-test between PSWI and NSWI for each smoothing kernel size. Results: The significance of comparisons increased with increasing smoothing kernel sizes. Signals from NSWI were greater than those from PSWI. The smoothing kernel size of four was optimal to use voxel-based comparisons. The bilaterally different areas were found on multiple brain regions. Conclusion: The paramagnetic (positive) phase mask led to reduce signals from high susceptibility areas. To minimize partial volume effects and contributions of large vessels, the voxel-based analysis on SWI with masked non-brain components should be utilized.
Keywords
Susceptibility weighted imaging; Phase mask; Brain tissue-mask; Smoothing kernel size Voxel-wise analysis;
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