DTI (6 or more diffusion directions)

The tensor field calculation for 6 diffusion encoding gradient directions is based on an analytical solution of the Stejskal and Tanner s diffusion equation system. For acquired datasets with more than 6 diffusion encoding gradient directions, a least-square approach using Singular Value Decomposition (SVD) is used. Datasets hosting an arbitrary number of diffusion directions can be analyzed, where either the gradient configuration is read from the DICOM header or from a text-file provided by the user.

Prior to launching the DTI analysis module in nordicICE, it is of vital importance that the images are recognized as a 4-dimensional time-series, and that the images are sorted according to image-number. This will be the case by default if the images were loaded either using the DICOM reader interface (see “ DICOM Reader ” ) or the DICOM server interface (see “ DICOM database ” ).

Once loaded, the Diffusion Tensor Imaging tab can be displayed by selecting Diffusion Analysis (DTI) on the Modules menu.

Note that you can also run the DTI analysis using the BOLD/DTI Wizard .

See reference guide Diffusion Tensor Imaging tab for a detailed description of the various options and settings.

Generating DTI maps

If nordicICE was able to read the DTI gradient configuration from the DICOM header, this information will be indicated in the "Number of gradient directions" and "Number of b0 images per slice" fields. If these fields states "Not specified", nordicICE was unable to extract the necessary information from the images itself, and manual specification becomes necessary.

Define the desired "Preprocessing options", select the requested output images to be generated and click "Process" button to calculate the parametric maps. These generated maps will appear as additional image windows in the nordicICE workspace:

Various measurements can now be performed on the output parametric images using the Region of Interest analysis feature in nordicICE (see “ Region of interest (ROI) Analysis ” ). This enables e.g. histogramming of Fractional Anistropy indices, ADC-values etc.

All generated parametric images can also be saved to any of the file formats supported by nordicICE (see “ Save Data ” ) or as a new patient series to the DICOM database.

You may also want to use the calculated diffusion tensors to reconstruct white matter fiber tracts, see “ Fiber Tracking ” . Click the 'Launch 3D viewer' button the open the MPR window for 3D visualization and interaction with the fiber tracts.