NA-MIC/Projects/NA-MIC Kit/Coordinate Systems

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Objective: To provide the infrastructure necessary to represent, manage, and transform between the variety of coordinate frames used in medical imaging.

Progress: Coordinate frame support is required at 3 distinct levels: low level library support via ITK and NRRD, application level support in Slicer3 via MRML, and execution model support via the command line modules.

1. A new image class, itk::OrientedImage, has been developed and added to ITK. This image class caches the image direction cosines. ITK's IO mechanisms have been updated to read and write orientation information. Filters which implictly manipulate orientation (flip, resample, etc.) have been modified to explictly modify the cached image orientation. NRRD support has been expanded to include specification of the patient coordinate frame but also the gradient coil measurement frame.
2. Slicer3 employs an RAS coordinate frame and manages coordinate frame relationships between various data using transform nodes in the MRML scene. Slicer3 leverages ITK IO factory mechanism to provide a variety of image file formats. Since ITK is uses an LPS coordinate frame (matching DICOM conventions), Slicer3 manages conversions from RAS <-> LPS during IO.
3. The execution model infrastructure in Slicer3

Key Investigators:

• GE Research: Bill Lorensen, Jim Miller
• Isomics: Steve Pieper

Links:

• Image Orientation in ITK
• Execution Model Reference Systems