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1. I need to be efficient
Our oversimplified example on a plane (one array
of voxels or one image):
scerma does not vary with θ within ΔΩ
→
less
fitting for B
θ
, b
θ
BUT
•
I still need to evaluate D
i->j
for all points j at
different radial distance
OR
•
I could evaluate D
i->j
only for j at exactly θ
0
, φ
0
Hence each
cone
defined by ΔΩ is
collapsed
to
its main axis and
scerma from each point is
transported along lines defined by the
directions from volume discretization in ΔΩ
(order of evaluations required~MN
4
)