[Insight-users] QuaternionGradientDescent

[ravi sharma]

Hi,
  I am now using QuaternionGradientDescentOptimizer
for 3D Registration.I am using a
MultiResolutionstrategy and am trying to align images
that are of by about 12 degrees over a rotation axis
and 3 to 4 mm translations.I am using
MattesMutualInformation as my metric.
  I set the quaterniontransform parameters
as{0,0,0,1,0,0,0} which is the identity transform.The
problem is that I just cant fathom what learning rate
to use.If I use a learning rate of 0.3 at level 0 of
registration then step size becomes so big that the
final image is even more misaligned(20 iterations at
level 0..increasing at subsequent levels) but if I use
a learning rate of 0.01 it makes no change to the
moving image.If there is a way to check passing Local
Optima with larger step sizes please tell me or if any
other suggestions then I shall be thankful.
  Ravi Sharma

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