fmri_spheremask

Description

FMRI_SPHEREMASK Spherical ROI mask centred on a given voxel. Creates a vectorized binary brain mask (228453 x 1) where all voxels within a sphere of the specified radius around the centre voxel are set to 1. Useful for creating seed regions for connectivity analyses.

Usage

s = fmri_spheremask(center, radius)

Inputs

  • CENTER: Centre of the sphere as voxel subscripts [x y z] (1 x 3), or as a linear brain index (scalar). For MNI coordinates, first convert: center = fmri_mni2sub([x y z]).

  • RADIUS: Sphere radius in voxels (1 voxel = 2mm). Default: 2 (= 4mm).

Outputs

  • S: Binary brain mask (228453 x 1). 1 = inside sphere.

Examples

% 10mm sphere at MNI [20 -58 18]
mask = fmri_spheremask(fmri_mni2sub([20 -58 18]), 5);
% Seed time series for FC
seed_ts = mean(data(logical(mask), :), 1);
r = fmri_corregressor(seed_ts', data);

See Also

  • fmri_regionmask

  • fmri_mni2sub

  • fmri_corregressor