Normalize Volumes by Removing Mean Offset

Fast removal of volume-wise mean offset from 4D neuroimaging data. Each volume/timepoint is centered to have zero mean across voxels.

Usage

normalize_volumes(vec, mask = NULL)

Arguments

vec

A NeuroVec object (4D neuroimaging data)

mask

Optional NeuroVol mask. If NULL, uses all non-zero voxels.

Value

A NeuroVec with each volume centered to zero mean

Details

This function removes global signal offset that can vary across timepoints due to scanner drift, physiological noise, or other factors. For each timepoint t:

$$output[,,,t] = input[,,,t] - mean(input[,,,t])$$

Uses fast C++ parallel implementation via RcppParallel.

Examples

if (FALSE) { # \dontrun{
vec <- neuroim2::read_vec("functional.nii.gz")
vec_normalized <- normalize_volumes(vec)
} # }