gdimap (version 0.1-1)

sph.odfvxgrid: Glyph Maps

Description

sph.odfvxgrid produces glyph-map fields of reconstructed ODF profiles for voxels in slices.

Usage

sph.odfvxgrid(fbase=NULL, rg=c(1,1), swap=FALSE, btoption=1, threshold=0.4,
 kdir=4, zfactor=5, snapshot=FALSE, showimage="glyphgfa", bview="coronal",
 savedir=tempdir(), pngfig="odfglyphs", bg="white", texturefile=NA, order=4)

Arguments

fbase

Directory where the required input data files are located.

rg

range of slices to process (default option rg=c(1,1)); rg=NULL processes all slices.

swap

toggle radiological/neurological orientation (default: FALSE).

btoption

b-table selection using the included data file btable.txt (btoption=1) or user defined files. With btoption=2, diffusion data files data.bvec and data.bval are selected for input, as used

threshold

thresholding generalized fractional anisotropy (GFA) value at each voxel (default: 0.4).

kdir

maximum number of fibre directions to map (default: 4).

zfactor

parameter controlling z-value in relief overlay maps (default: 5).

snapshot

logical variable controlling line-maps snapshots (default: FALSE).

showimage

object controlling visualization of line-maps (default: "glyphgfa"). Alternative options are: c("none", "gfa", "glyph", "glyphgfa", "glyphrgbmap", "glyphdata") (see Details).

bview

MRI slice view selection in {axial, coronal, sagittal} (default: "coronal").

savedir

directory for saving/loading processed results (default: tempdir().

pngfig

base-name of the PNG file when snapshot is TRUE (default "odfglyphs").

bg

map background colour (default "white")

texturefile

name of the PNG file to be used as RGB map overlay in some 'showimage' options (default NA - no texture).

order

parameter associated with the order of the spherical harmonics approximation (default: 4).

concept

• GQI Volume Processing
• Glyph maps

Details

Slice glyph map display and overlay selection is controlled by specifying one the arguments c("none", "gfa", "glyph", "glyphgfa", "glyphrgbmap", "glyphdata") for showimages. Meanings are as follows: "none" - no overlay; "gfa" - GFA map only; "glyph" - glyph map only; "glyphgfa" - GFA overlayed on glyph map; "glyphrgbmap" - glyphs overlayed on RGB map (if available); "glyphdata" - data_brain.nii.gz is overlayed on line map.

Q-ball imaging (QBI) is used for orientation distribution function (ODF) reconstruction. One QBI-compatible b-table defining the acquisition setup on a S2-shell is included in the package. The b-table btable.txt has 203 points distributed on a S2-shell.

References

Ferreira da Silva, A. R. Facing the Challenge of Estimating Human Brain White Matter Pathways. In Proc. of the 4th International Joint Conference on Computational Intelligence (Oct. 2012), K. Madani, J. Kacprzyk, and J. Filipe, Eds., SciTePress, pp. 709-714.

Tuch D. S., Q-Ball Imaging, Magnetic Resonance in Medicine 52 (2004), 1358-1372. Tabelow K., Polzehl J.: dti: DTI/DWI Analysis, 2012. R package version 1.1-0.

See Also

sph.odfpeaks, sph.odfvmf, sph.odfvmflines, s2tessel.zorder, plotglyph, rgbvolmap, simulglyph.vmf, simul.fandtasia, simul.simplefield

Examples

## show glyph-map for selected slice
  sph.odfvxgrid(threshold=0.5, showimage="glyphgfa")
  ##----
  ## generate slice RGB map as texture
  rgbvolmap(texture=TRUE, transp=TRUE)
  ## coronal glyphs + RGBmap
  sph.odfvxgrid(threshold=0.5, showimage="glyphrgbmap",
    texturefile=paste(tempdir(),"/rgbmap.png", sep=""))