[vtkusers] Question about parameters for running the Attenuation.tcl script

[Lino Ramirez]

Hello,

I have been running the script Attenuation.tcl from the CD that comes with
the VTK textbook book (actually I converted the code to C++) for correcting
the attenuation that appears when using surface coil MR scanners. The code
works fine. However, I am wondering if someone can give me some rules of
thumb for setting the following values:

* The center of the sphere (by the way, is there any particular reason for
selecting a sphere as sampling function?)

* The radius of the sphere

* The scale for vtkImageShiftScale

Thank you,

Lino Ramirez

P.S. here is a copy of the code for Attenuation.tcl
# Show the constant kernel.  Smooth an impulse function.

catch {load vtktcl}
if { [catch {set VTK_TCL $env(VTK_TCL)}] != 0} { set VTK_TCL
"../../examplesTcl" }
if { [catch {set VTK_DATA $env(VTK_DATA)}] != 0} { set VTK_DATA
"../../../vtkdata" }


vtkPNMReader reader
reader SetFileName "$VTK_DATA/AttenuationArtifact.pgm"

vtkImageCast cast
cast SetInput [reader GetOutput]
cast SetOutputScalarTypeToFloat

# get rid of discrete scalars
vtkImageGaussianSmooth smooth
smooth SetDimensionality 2
smooth SetInput [cast GetOutput]
smooth SetStandardDeviations 0.8 0.8 0

vtkSphere m1
m1 SetCenter 310 130 0
m1 SetRadius 0

vtkSampleFunction m2
m2 SetImplicitFunction m1
m2 SetModelBounds 0 264 0 264 0 1
m2 SetSampleDimensions 264 264 1

vtkImageShiftScale m3
m3 SetInput [m2 GetOutput]
m3 SetScale 0.000095

vtkImageMathematics m4
m4 SetInput1 [m3 GetOutput]
m4 SetOperationToSquare
m4 BypassOn



vtkImageMathematics m5
m5 SetInput1 [m4 GetOutput]
m5 SetOperationToInvert

vtkImageShiftScale m6
m6 SetInput [m5 GetOutput]
m6 SetScale 255

vtkImageShiftScale t2
#t2 SetInput [t1 GetOutput]
t2 SetScale -1

#vtkImageMathematics m3
#m3 SetInput1 [t2 GetOutput]
#m3 SetOperationToInvert
#m3 ReleaseDataFlagOff

vtkImageMathematics div
div SetInput1 [smooth GetOutput]
div SetInput2 [m3 GetOutput]
div SetOperationToMultiply

vtkImageViewer viewer
viewer SetInput [div GetOutput]
#viewer SetInput [cast GetOutput]
viewer SetColorWindow 256
viewer SetColorLevel 127.5
#viewer ColorFlagOn

# make interface
source WindowLevelInterface.tcl