FT_DATATYPE_VOLUME describes the FieldTrip MATLAB structure for volumetric data.
The volume data structure represents data on a regular volumetric
3-D grid, like an anatomical MRI, a functional MRI, etc. It can
also represent a source reconstructed estimate of the activity
measured with MEG. In this case the source reconstruction is estimated
or interpolated on the regular 3-D dipole grid (like a box).
An example volume structure is
anatomy: [181x217x181 double] the numeric data, in this case anatomical information
dim: [181 217 181] the dimensionality of the 3D volume
transform: [4x4 double] affine transformation matrix for mapping the voxel coordinates to the head coordinate system
unit: 'mm' geometrical units of the coordinate system
coordsys: 'ctf' description of the coordinate system
Required fields:
- transform, dim
Optional fields:
- anatomy, prob, stat, grey, white, csf, or any other field with dimensions that are consistent with dim
- unit, size, coordsys
Deprecated fields:
- dimord
Obsoleted fields:
- none
Revision history:
(2014) The subfields in the avg and trial fields are now present in the
main structure, e.g. source.avg.pow is now source.pow. Furthermore, the
inside is always represented as logical array.
(2012b) Ensure that the anatomy-field (if present) does not contain
infinite values.
(2012) A placeholder 2012 version was created that ensured the axes
of the coordinate system to be right-handed. This actually never
has made it to the default version. An executive decision regarding
this has not been made as far as I (JM) am aware, and probably it's
a more principled approach to keep the handedness free, so don't mess
with it here. However, keep this snippet of code for reference.
(2011) The dimord field was deprecated and we agreed that volume
data should be 3-dimensional and not N-dimensional with arbitary
dimensions. In case time-frequency recolved data has to be represented
on a 3-d grid, the source representation should be used.
(2010) The dimord field was added by some functions, but not by all
(2003) The initial version was defined
See also FT_DATATYPE, FT_DATATYPE_DIP, FT_DATATYPE_SOURCE