Master's Thesis - Studierstube Augmented Reality Project - Graz ...

4.3 Intermediate File Format
a simple subsequent rigid registration is sufficient provided that the 100x100 ROI was
set reasonable.
Moreover, the PC-MRI method shows two systematic errors. Additional phase
shifts occur because of
• Eddy currents and
• Concomitant gradient fields.
Concomitant gradient fields can be corrected in a low order during image reconstruction
with known gradient pulses [Bernstein1998], so they can be neglected further
on.
For the remaining error a software based baseline correction can be performed with
the 4D Flow Toolbox calculation tool using two different operating modes. A standard
derivation correction can be performed in the case of ”enough” 1 images and a user
defined ROI correction in the other case. Details for these kinds of corrections can be
learned from [Kouwenhoven1995; Reiter2006; Partanen1995].
4.3 Intermediate File Format
As so far defined the intermediate result files are an essential part of this work since
further visualizations utilize this information. These files are arranged as follows: One,
rather small, central information file (master file) can be used to find all other related
files and the DICOM database (most likely a DICOMDIR file on a CD or harddisk).
For every image slice there is one file containing headers and meta data for all image
types of all times followed by drawings and all the vector data (data files).
Example: 3D parallel mode, 20 slices, 42 times per slice. Assuming that
three rephased images per slice and time exist, there is one central information
file and 20 slice files. In every slice file there is one general header
containing information about the contained data, followed by 42*6 image
headers (3 rephased and 3 phase-contrast images per time step) containing
image meta data. After that header section there is one section containing
the vector data related to those images, followed by the drawings and
1 ”enough” is experientially determinated with three to four images
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