Anisotropy

The Anisotropy plug-in is used to quantify the directionality of trabecular bone. More generally, the degree of anisotropy measure tells you whether a structure has a certain orientation or not. The anisotropy algorithm is fairly complex and has multiple steps:

1. Determine mean intercept length (MIL) for n vectors
2. Plot MIL vectors into a point cloud
3. Solve the equation of an ellipsoid that best fits the point cloud
4. Calculate the degree of anisotropy from the radii of the ellipsoid

In the first step the algorithm draws a set parallel lines L over the input image in the direction of v, where v is a unit vector with a random orientation. Then for each line it counts the number of phase changes p, i.e. where the line enters from background to foreground. MIL is the sum of ||l_i|| / p_i, l ∈ L, i.e. the lengths of the lines divided by their phase changes. The first step is repeated n times, and in each a vector v * MIL is added to a point cloud.

After plotting the MIL vectors...

Fractal dimension

• Menu path: Plugins>BoneJ>Anisotropy
• Input paremeters
  • ImgPlus<T> inputImage
  • Integer directions
  • Integer lines
  • Double samplingIncrement
  • long translations
  • boolean recommendedMin
  • boolean printRadii
• Output parameters
  • Table<DefaultColumn<String>, String> resultsTable
• Calls
  • MILPlane in org.bonej.bone-ops (to be moved to net.imagej.imagej-ops or other fitting artefact)
  • Quadric in net.imagej.imagej-ops
  • QuadricToEllipsoid in org.bonej.bone-ops (to be moved to net.imagej.imagej-ops or other fitting artefact)

Setup dialog

Messages

• If there's no image open
  • Show an error dialog
  • Abort the run
• If the input image is not binary
  • Show an error dialog
  • Abort the run
• If the input image doesn't have three spatial dimensions
  • Show an error dialog
  • Abort the run

Results

Differences from BoneJ1

Future