WMH Replacement and WMH Replacement and Image WarpingImage Warping

Evan FletcherEvan Fletcher

Purpose of methodPurpose of method

Use warping to compile statistical profiles Use warping to compile statistical profiles of WMH distributionsof WMH distributions

Goal Goal

Prevent overestimation of ventricles during Prevent overestimation of ventricles during warpingwarping

Obtain warped image with WMH voxels Obtain warped image with WMH voxels outside template ventricles (not inside!)outside template ventricles (not inside!)

Overview of methodOverview of method

Warp Template to T1 imageWarp Template to T1 image Inverse transform WMH distribution masks Inverse transform WMH distribution masks

onto templateonto template Create frequency maps on templateCreate frequency maps on template Compare with FA images where Compare with FA images where

appropriateappropriate

Steps in the MethodSteps in the Method

Produce WMH mask by filtering FLAIR Produce WMH mask by filtering FLAIR imageimage

Linearly align FLAIR to T1 subject imageLinearly align FLAIR to T1 subject image Readjust WMH intensities in T1 to Readjust WMH intensities in T1 to

minimize warping errorsminimize warping errors Warp T1 and TemplateWarp T1 and Template

WMT alignment & tissue WMT alignment & tissue replacement replacement

Accuracy Issues Accuracy Issues

Low resolution of FLAIR images causes Low resolution of FLAIR images causes inaccuracies when reslicing to T1 space. inaccuracies when reslicing to T1 space.

Partially address these by thresholding Partially address these by thresholding resliced imageresliced image

WMH voxels appear dark in T1 image. WMH voxels appear dark in T1 image. Estimate replacement value by local mean Estimate replacement value by local mean of white intensityof white intensity

Composite maps from warpingComposite maps from warpingAccurate placement of periventricular lesions warped onto templateAccurate placement of periventricular lesions warped onto template

3D view: ventricles Slice view3D view: ventricles Slice view