Slice selection. For each point along the centerline of a canal, a local coordinate system composed of tangent, normal and binormal vectors (

*t̂*,

*n̂*_{1} and

*n̂*_{2}, respectively) was calculated directly from the centerline, s. A ~500

*μ*m-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:

. 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-

*μ*m slices,

*d*_{max} is set to 250

*μ*m (e.g., the point of distance

*d*_{1} would be selected as part of the slice while the point of distance

*d*_{2} would not).

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