  The smooth muscle bundles (SMBs) in the bladder act as contractile elements
which enable the bladder to void effectively. In contrast to skeletal muscles,
these bundles are not highly aligned, rather they are oriented more
heterogeneously throughout the bladder wall. In this work, for the first time,
this regional orientation of the SMBs is quantified across the whole bladder,
without the need for optical clearing or cryosectioning. Immunohistochemistry
staining was utilized to visualize smooth muscle cell actin in multiphoton
microscopy (MPM) images of bladder smooth muscle bundles (SMBs). Feature
vectors for each pixel were generated using a range of filters, including
Gaussian blur, Gaussian gradient magnitude, Laplacian of Gaussian, Hessian
eigenvalues, structure tensor eigenvalues, Gabor, and Sobel gradients. A Random
Forest classifier was subsequently trained to automate the segmentation of SMBs
in the MPM images. Finally, the orientation of SMBs in each bladder region was
quantified using the CT-FIRE package. This information is essential for
biomechanical models of the bladder that include contractile elements.
