[Insight-users] Wierd metric value for subregion of image

[motes motes]

I am trying to compute the metric value for 4 subregions in a 512*512
image pair (fixed, moving). All regions have the size (256, 256) which
gives the following 4 regions:


Region 0 (lower left corner):
start index = (0,0)

Region 1 (lower right corner):
start index = (256,0)

Region 2 (Upper left corner):
start index = (0, 256)

Region 3 (Upper right corner):
start index = (256, 256)


The moving image is deformed increasingly for each region in the
following order: D(R0) < D(R1) < D(R2) < D(R3) using a 8*8
BSplineDeformableTransform:

    0  0    0  0    0  0    0  0              0  0    0  0    0  0    0  0
	
    0  0    20 20    20 20    0  0         0  0    40 40    40 40    0  0

    0  0    20 20    20 20    0  0         0  0    40 40    40 40    0  0
	
    0  0    0  0    0  0    0  0             0  0    0  0    0  0    0  0


	
    0  0    0  0    0  0    0  0             0  0    0  0    0  0    0  0

    0  0    0  0    0  0    0  0             0  0    10 10    10 10    0  0
	
    0  0    0  0    0  0    0  0             0  0    10 10    10 10    0  0
	
    0  0    0  0    0  0    0  0             0  0    0  0    0  0    0  0


But when I compute the metric I get som rather unexpected values:


subRegion = ImageRegion (0148EF70)
  Dimension: 2
  Index: [0, 0]
  Size: [256, 256]
value = 6490.59


subRegion = ImageRegion (0148EF70)
  Dimension: 2
  Index: [0, 256]
  Size: [256, 256]
value = 704.728


subRegion = ImageRegion (0148EF70)
  Dimension: 2
  Index: [256, 0]
  Size: [256, 256]
value = 9512.77


subRegion = ImageRegion (0148EF70)
  Dimension: 2
  Index: [256, 256]
  Size: [256, 256]
value = 2481.78


I would expect that the region starting in index (0,0) should almost
be 0. This is also verified from the following images (fixed, moving
and difference respectivily):

http://img6.imageshack.us/img6/994/82602924.jpg

Am I defining the start index in the fixed image wrong?