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Changel coordinate system from 3d image (CT-Scan)

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  • Changel coordinate system from 3d image (CT-Scan)

    I am using ITK-SNAP to label specific hip markers in a CT-Scan image. However, I want to change to the 3d-coordinate system such that it has the same axis's as our motion analysis software (Vicon Nexus). The CT scan has its own default coordinate system, and from there I can get the position of the 6 important markers. BUT, I want to change the coordinate system such that the Left ASIS, and the Right ASIS form a line in the x-axis (such that they translate only in the x-direction, but are not translated in the y,z-directions). I want this to orthogonally intersect with the PSIS markers in the y-axis.

    I have been reading up on 3d image restoration, and transformation/rotation matrix methods, but I still not have been able to fully solve how to change the coordinate system.

    Any ideas?

  • #2
    Re: Changel coordinate system from 3d image (CT-Scan)

    Hi Kevin,

    There are several approaches to registering CT/MRI data files to kinematic data. You may want to take a look at the following link:

    The basic procedure is two steps: i) determine the transform that aligns the CT/MRI points to the markers of the Nexus coordinate space. ii) transform the points of i) to the coordinate system of your segment. The math/procedure to do the conversion you are looking to accomplish probably goes beyond this thread but I would be happy to share it with you off site.

    Innovative Sports Training
    Providing turnkey real-time 3D motion capture systems and analysis software for use in biomechanics research, clinical rehabilitation and sports.