Segmentation: Cerebellar White Matter

General Description Similar to the cerebrum, the cerebellum has a network of white matter connecting different areas of the cerebellum or connecting the cerebellum to the rest of the brain. The white matter is most dense in the medial anterior areas of the cerebellum and disperses as you go more posterior and lateral. In the most anterior slices the cerebellar white matter is similar to two round masses hanging off of the brainstem, and you move more posterior the balls of white matter begin to have strings of white matter coming off of them. More posterior and in the medial part of the cerebellum the white matter begins to resemble two birds touching beaks at the midline. In the most posterior extent of the cerebellar white matter, the white matter becomes a bunch of white matter streaks which become smaller and more disperse and you move more posteriorly until finally, they disappear. The white matter of the cerebellum does not touch the outside of the exterior of the cerebellum except across the medial border (similar to the corpus callosum in the cerebral white matter).
Procedure Segmentation The histogram method is used to give the contour of the white matter.
	Finding the beginning of cerebellar white matter vs. the brainstem is very tricky because in most cases the white matter shows up before any cerebellar exterior. Our convention for this area is as follows: within a two slice span (120 slice scan) before the appearance of the cerebellum, the posterior part of the brainstem there is a dramatic change in the lateral extent of the brainstem, based on color contrast and the appearance of the cerebellum. The more anterior of the two slices will contain a uniformly colored structure which is extracted singularly and labeled brainstem (there is not cerebellar exterior at this point). However, on the more posterior of the two slices, the lateral extremities of the brainstem are no longer taken as part of the brainstem outline. They are extracted separately as cerebellar white matter and again as cerebellar exterior. With the contrast increased it is easy to see the division between cerebellar white matter and brainstem. This division can be manually drawn in or it may be possible to use the contour function. The next slice (moving posteriorly) would have cerebellum exterior present, and these extremities will again be extracted as cerebellar white matter as given by the histogram.
		The histogram is taken from the whole area of the cerebellar hemispheres outline. The contour may need some manipulation especially in different areas of the cerebellum. This can be done by right clicking and dragging the averaging line (red line) in the histogram. Averaging the two highest peaks in the histogram should give the right contour.
	This works for the most part until you reach the most posterior portion of the white matter. Often the white matter border in the posterior portion is best given by averaging the middle highest peak with the peak (not necessarily the tallest peak) to the far right.

Labeling
This outline should be labeled "cerebellar white matter."

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