Re: [Insight-users] Bspline-based registration example 6

[Tomáš Kazmar]

Hi Eve,

# always true that the 2nd level uses more nodes (less spacing) in multi-level
I do not think using less nodes would make sense, just consider what it
means, by using less nodes you restrict what deformations can be
represented.

# The claim says: "the spacing between the control points is increased by a
# factor of 2 [at the second level]" (p. 5)
It seems to me that it refers to the levels of pyramid in the opposite direction
than you suppose.

Your other questions are quite interesting and I hope someone more
competent will answer them.

# 1. Are there heuristics of determining the optimal choice of 1) # of nodes
# and 2) # of levels for nD-image? 
# 
# 2. I tried a 2-level scheme, where in the 2-level, I input finer-sampled
# images. Despite the change in resolution and more parameters (nodes), there
# is no change in the deformation (though the metric did changed, and that 1st
# level computed deformation was suboptimal)? I also tried decreasing the
# number of nodes (due to the scheme in aforementioned paper), with the same
# result. Is this reasonable?
# 
# 3. Is it correct that more nodes don't necesary result in more accurate
# registration due to possible unstable behaviour?


Regards,
Tomas