BrainVoyager supports different coordinate systems. The same dataset can be stored in different coordinate systems at different points within the data processing pipeline.
The main supported coordinate systems are
- Native
- Talairach
- MNI
In addition, the data may be stored with the reference space property “unknown”, “ACPC” or ”mTAL”.
Native Space - BrainVoyager system coordinates (SYS)
When creating an anatomical or functional document in BrainVoyager, it will first be represented in native space. This spatial reference property can also be checked within the document properties dialog of a currently loaded document.
In case of “native” and “ACPC space”, BrainVoyager uses so called “system coordinates”.
origin of coordinate system:
X=128, Y=128, Z=128
axes arrangement:
X = Left – Right
Y = Anterior – Posterior
Z = Inferior - Superior
The system coordinates are also displayed on the “3D Coords” tab of the 3D Volume tools when opening a VMR document.
BrainVoyager internal coordinates (BV)
In the background BrainVoyager uses the so called BrainVoyager internal coordinates.
origin of coordinate system:
X=128, Y=128, Z=128
axes arrangement:
X = Anterior – Posterior
Y = Inferior - Superior
Z = Left - Right
Talairach space (TAL) and MNI space (MNI)
origin of coordinate system:
X=0, Y=0, Z=0
axes arrangement:
X = Left – Right
Y = Anterior – Posterior
Z = Inferior - Superior
Transformations between Coordinate System
To transform from BrainVoyager System coordinates to Talairach or MNI coordinates, the following simple subtraction step can be applied:
Tal X = 128 – BV SyS X
Tal Y = 128 – BV SyS Y
Tal Z = 128 – BV SyS Z
The transformation steps to get from one spatial representation to another are stored within corresponding transformation (.trf) files.
More details can be found in the attached PDF.