Elastix initial guess parameters

Hi Forum,

I have a bit of a technical issue with the Elastix registration. What I want to do is do co-align two images with vastly different dimensions (Fixed image 300x300 registered with moving image 15kx15k).The target image is largely background, the target object is about 100x100 pixels large.

My current workaround (which works for most cases) is to do the following: I mask both images and use a multi-resolution strategy with A LOT of downsampling:

(Registration "MultiResolutionRegistration")
(NumberOfResolutions 5)
(FixedImagePyramidSchedule 56 56 16 16 8 8 2 2 1 1)

(AutomaticTransformInitialization "true")
(AutomaticTransformInitializationMethod "GeometricCenter")

But for a number of mask pairs this approach fails, nonetheless. Now, according to the log, inital transform parameters are initialized along the way:

Transform parameters are initialized as: [1, 0, 0, 1, -118.99999923405684, -128.99999923405684]

What I would like to do is to manipulate these parameters and set them to [X, 0, 0, X, -118.99999923405684, -128.99999923405684], for instance.
Does the parameter file allow something like that? I figured it could be related to the Scales parameter, but I’m not 100% sure how to handle it.

Thanks in advance!
Johannes

1 Like