BrainVoyager version: 22.4.6
Dataset used: Getting Started Guide data

This document shows in a step by step example how to transform VOI files to different reference spaces, i.e. to Native, ACPC, Talairach and MNI space.

From Native to MNI Space and from MNI to Native Space

To start, we open a Native VMR document, in this case from sub-01. We also load a VOI file in Native space that has been created based on the individual anatomy of subject sub-01.

Note: The reference space of that specific VOI file has been marked as 'Native' in the 'Volumes-Of-Interest' dialog.

Please click on 'Options...' to invoke the 'VOI Analysis Options'.

In the 'Transformations' tab we need to specify the required information to transform the Native VOI to an MNI VOI:

We need to select the MNI transformation file *_TO_MNI_a12_adjBBX.trf, the resulting *_MNI.vmr as Target VMR and we need to specify that the transformation has to be applied forward. The resulting VOI file name is a combination of the original VOI file name _ the transformation direction (forward - FWD or backward BWD) _ the target VMR.

We can start the transformation by clicking on 'Apply TRF'.

After the conversion is complete BrainVoyager will automatically open the resulting VOI file in MNI space:

We can also back-transform the newly created MNI VOI to Native space. To do that we follow the same steps, but apply the transformation backward and change the Target VMR to the Native VMR of sub-01:

The resulting Native VOI should be (almost) identical to the original Native VOI:

When you inspect the 'VOI Center-Of-Gravity Table' ('Options...' -> 'VOI Functions' tab -> 'Table' button in 'Overview table with VOIs center of gravity' field) for both the original and the back-transformed Native VOI, you will notice some small differences especially in the voxel count. This can be ascribed to the sampling of voxels for the VOI conversion.

The workflow for the VOI conversion between all other reference spaces is very similar to the one described above, only different transformation files and Target VMRs have to be specified for the conversion step.

From Native to ACPC Space and from ACPC to Native Space 

Below you can find screenshots of the initial VOI, the necessary files for the VOI conversion and the resulting VOI.

For the back-transformation of the ACPC VOI to Native Space the following files have to be specified:

The resulting back-transformed native VOI will be almost identical.

Also here small differences in VOI size can be found between the original and the back-transformed Native VOI.

From ACPC to TAL Space and from TAL to ACPC Space 

Below you can find screenshots of the initial VOI, the necessary files for the VOI conversion and the resulting VOI.

For the back-transformation of the Talairach VOI to ACPC Space the same file has to be specified again, but this time the button 'TAL - ACPC' needs to be used.

The resulting back-transformed ACPC VOI will be almost identical.

Also here small differences in VOI size can be found between the original and the back-transformed ACPC VOI.