Parameter settings for deformable b spline registration of CT/MRI based sCT for pelvis

[DVersnel]

Hi all,

I was wondering if there are some parameters I should play around with other than grid spacing for optimizing (bulk density) sCT to CT registration (pelvis). With the current parameters there often is slight misalignment when looking at the bones. I don't believe there's a preset in the model zoo as well for this purpose. Thanks in advance!

Settings:
(Transform "BSplineTransform")
(NumberOfResolutions 4)

// Image pyramid schedule
(ImagePyramidSchedule 8 8 4 4 2 2 1 1)

// Optimizer settings
(Optimizer "AdaptiveStochasticGradientDescent")
(MaximumNumberOfIterations 1000)
(SP_a 400.0) 
(SP_A 20.0)
(SP_alpha 0.602)
(AutomaticParameterEstimation "true")
(UseAdaptiveStepSizes "true")

// Metric settings
(Metric "AdvancedMattesMutualInformation")
(NumberOfHistogramBins 64)
(FixedImagePyramid "FixedSmoothingImagePyramid")
(MovingImagePyramid "MovingSmoothingImagePyramid")

// Registration settings
(Registration "MultiResolutionRegistration")
(FixedInternalImagePixelType "float")
(MovingInternalImagePixelType "float")

// Image sampler settings
(ImageSampler "Random")
(NumberOfSpatialSamples 4096)

// B-spline grid settings
(FinalGridSpacingInVoxels 16 16 16) // 

// Regularization
(FinalBSplineInterpolationOrder 3)
(GridSpacingSchedule 16 16 16 8 8 8 4 4 4 3 3 3)

// Interpolator settings
(Interpolator "BSplineInterpolator")

// Resampler settings
(Resampler "DefaultResampler")
(DefaultPixelValue 0)
(ResultImagePixelType "short")
"""