Complex Image Set

A complex image set cannot be represented by a single grid. Instead it is made up of multiple grids, because it includes things like:

1. gantry tilt
2. irregular slice spacing
3. overlapping scans

Proposed data structure shown in pseudocode

// The superclass is the reformatted image.  It is a standard itk image with uniform spacing & direction cosines.
// The memory for the superclass image is not allocated until reformatting occurs.
itkImageCollection : itkOrientedImage {
  // The sourceImageGroup is an array of image sections.  Each image 
  // section corresponds to a group of slices with the same tilt, spacing, etc.
  itkArray<itkOrientedImage> sourceImageGroup;
}

Normal ITK routines will operate on the reformatted image, using C++ inheritance. But if the user needs the original images or their headers, they are available.

At image load time, the image should be loaded as an image collection. By default, reformatting will occur automatically using the spacing found in the largest source image. If reformatting is not desired, the programmer must specify no reformatting prior to load.

After reformatting, the images within the source image group may be deallocated to save memory. Deallocation can refer to the image data only (retaining header information for the image group items), or the entire group may be destroyed (leaving only the reformatted image).

By default, the image save will write the reformatted image to disk. When saving as source image format, the reformatted image is first interpolated back to the source image space by the programmer.

See Also

Note from the ITK community about ITK 4.0 planning:

http://www.itk.org/Wiki/ITK_Release_4.0#Oriented_Images

Slicer bug 595

http://www.na-mic.org/Bug/view.php?id=595