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= Two Images are far apart and do not overlap at all when viewed in Slicer =  
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= Can I manually adjust or correct a registration? =  
*'''Problem:''' when you place one image in the background and another in the foreground, the one in the foreground will not be visible (entirely) when switching bak & forth
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*'''Problem:''' obtained registration is insufficient
 
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*'''Explanation:''' The automated registration algorithms (except for  fiducial and surface registration) in Slicer operate on image intensity and try to move images so that similar image content is aligned. This is influenced by many factors such as image contrast, resolution, voxel anisotropy, artifacts such as motion or intensity inhomogeneity, pathology etc, the initial misalignment and the parameters selected for the registration.
*'''Explanation:'''Slicer chooses the field of view (FOV) for the display based on the image selected for the background. The FOV will therefore be centered around what is defined in that image's origin. If two images have origins that differ significantly, they cannot be viewed well simultaneously.
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*'''Fix:''' you can adjust/correct an obtained registration manually, within limits. As outlined below. Your first try however should be to obtain a better automated registration by changing some of the input and/parameters and then re-run. Some guidelines on this are listed [[Projects:SlicerFAQ:RegistrationRerun| '''here'''.]]
*'''Fix:''' recenter one or both images as follows:
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**'''Manual Adjustment''': If the transform is linear, i.e. a rigid or affine transform, you can access the rigid components (translation and rotation) of that transform via the [https://www.slicer.org/wiki/Modules:Transforms-Documentation-3.6 Transforms module].
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***#In the ''Data'' module, drag the image volume inside the registration transform node
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***#Select the views so that the volume is displayed in the slice views
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***#Go to the [https://www.slicer.org/wiki/Modules:Transforms-Documentation-3.6 Transforms module] and adjust the translation and rotation sliders to adjust the current position. To get a finer degree of control, enter smaller numbers for the translation limits and enter rotation angles numerically in increments of a few degrees at a time

Latest revision as of 17:10, 10 July 2017

Home < Projects:SlicerFAQ:RegistrationAdjust

Can I manually adjust or correct a registration?

  • Problem: obtained registration is insufficient
  • Explanation: The automated registration algorithms (except for fiducial and surface registration) in Slicer operate on image intensity and try to move images so that similar image content is aligned. This is influenced by many factors such as image contrast, resolution, voxel anisotropy, artifacts such as motion or intensity inhomogeneity, pathology etc, the initial misalignment and the parameters selected for the registration.
  • Fix: you can adjust/correct an obtained registration manually, within limits. As outlined below. Your first try however should be to obtain a better automated registration by changing some of the input and/parameters and then re-run. Some guidelines on this are listed here.
    • Manual Adjustment: If the transform is linear, i.e. a rigid or affine transform, you can access the rigid components (translation and rotation) of that transform via the Transforms module.
        1. In the Data module, drag the image volume inside the registration transform node
        2. Select the views so that the volume is displayed in the slice views
        3. Go to the Transforms module and adjust the translation and rotation sliders to adjust the current position. To get a finer degree of control, enter smaller numbers for the translation limits and enter rotation angles numerically in increments of a few degrees at a time