[ITK-users] [ITK] applying a transform to an ITK Point object results in it moving the opposite direction from the image

[Yaniv, Ziv Rafael (NIH/NLM/LHC) [C]]

Hello Andrew,

In ITK the result of a registration maps points from the fixed image coordinate system to the moving coordinate system, so T(p_f) = p_m and the TRE is || T(p_f) – p_m||. I suspect you just need to use the inverse transform.

You may be interested in this SimpleITK notebook (http://insightsoftwareconsortium.github.io/SimpleITK-Notebooks/Python_html/67_Registration_Semiautomatic_Homework.html) which has a linked cursor GUI (gui. RegistrationPointDataAquisition). The source code for the UI is here: https://github.com/InsightSoftwareConsortium/SimpleITK-Notebooks/blob/master/Python/gui.py .

      hope this helps
             Ziv




From: Andrew Harris <aharr8 at uwo.ca>
Date: Wednesday, June 28, 2017 at 3:14 PM
To: Insight-users <insight-users at itk.org>
Subject: [ITK-users] [ITK] applying a transform to an ITK Point object results in it moving the opposite direction from the image

Hi there,
I have been trying for a while to get this working: I want to be able to select corresponding points in a fixed and moving image, and determine how well the moving image is transformed to overlay the fixed image by using target registration error.  The problem is, using the same transform I applied to a moving image that translated it to the left, the point selected in the moving image gets translated to the right for example.

--

AH



Andrew Harris, Honours BSc (Medical Physics)

PhD (CAMPEP) & MClSc Candidate

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