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3.2.15 ITK Structural Registration

<ITK_structural_registration></ITK_structural_registration>

  • on Default Setting
  • off

If this setting is set to 'off' the registration pipeline in DIFF_PREP will be used. If it is 'on', an external ITK library program will be called to perform this registration.

The optimization procedure built into DIFF_PREP is adjusted to better handle small rotations or small transformation differences in between the structural and template images (beginning of step 2). If the registration step in between the structural and the template images does not converge or if that registration does not conform with user's expectations, the user has the option to use the ITK (Insight Toolkit) library to perform this registration.

Because the ITK registration is optimized to converge in most of the cases, the default setting for this option is 'on'. However, the registration of structural to template image will take slightly longer, and so the user is given the option to use the faster built in option.

ITK registration pipeline used is:

  • Initialization of translation with centre of mass of the two images.
  • Multi-scale registration of 3 resolution levels.
  • Mattes mutual information metric (number of bins is set 1.5 times the number of bins in the registration settings file).
  • Trilinear interpolation
  • 3D Rigid Versor transform (to handle large rotations)
  • Versor Gradient Descent optimizer (to handle non-linear nature of the versor transform space).