The Qcache recon-all flag completes the following:
- resample data onto the average subject (called fsaverage)
- smooth it at a range of FWHM (full-width/half-max) values, usually 0, 5, 10, 15, 20, and 25mm.
This flag is intended to speed up later processing and allow for rapid analysis of group data.
The QDEC utility for group analysis requires pre-cached files as an input. These files are created by running mris_preproc, which creates smoothed surface data files sampled to the 'fsaverage' common-space surface. By default, the surface data for thickness, curv, sulc, area and jacobian_white are smoothed at 0, 5, 10, 15, 20, and 25 mm FWHM. If just one set of surface data needs to be processed, then the option -measure <surfmeas> can follow -qcache, where <surfmeas> is one of: thickness, curv, sulc, area, jacobian_white or any surface measure. Multiple instances of -measure <meas> is supported. The -measuredir option allows specifying a directory other than the default of surf. Another option is -fwhm <num> where <num> is a value in mm. Also, -target <name> allows specifying a common-space target other than fsaverage (the default). qcache is also a target for make, eg. recon-all -make qcache. See also: http://surfer.nmr.mgh.harvard.edu/fswiki/Qdec