FIGURE 3.

Slice selection. For each point along the centerline of a canal, a local coordinate system composed of tangent, normal and binormal vectors (t̂, n̂₁ and n̂₂, respectively) was calculated directly from the centerline, s. A ~500 μm-thick slice was cut transverse to the canal as follows. If p̂_c is a vector extending from the origin of the global coordinate system to the center point, and p̂_n (n = 1,2,…) are vectors from the global system origin to the data points comprising the endolymphatic space, then d_n, the distance between a data point and a plane centered at the center point and perpendicular to the tangent vector (white plane) is given by the equation: $d_n=\frac{\widehat{t}•({\check{p}}_n-{\check{p}}_c)}{\mid \widehat{t}\left|\right|({\check{p}}_n-{\check{p}}_c)\mid }$. To designate slice thickness, only points of d_n < d_max are selected, corresponding to points falling between the white and shaded planes. In the specific case of 500-μm slices, d_max is set to 250 μm (e.g., the point of distance d₁ would be selected as part of the slice while the point of distance d₂ would not).