diminfo2fps: diminfo2fps

In AnalyzeFMRI: Functions for Analysis of fMRI Datasets Stored in the ANALYZE or NIFTI Format

Description

Extract freq.dim, phase.dim and slice.dim fields from the one byte dim.info field of a NIFTI header file.

Usage

diminfo2fps(dim.info)

Arguments

dim.info

dim.info field of a NIFTI header file

Value

A list containing freq.dim, phase.dim and slice.dim fields.

These are provided to store some extra information that is sometimes important when storing the image data from an FMRI time series experiment. (After processing such data into statistical images, these fields are not likely to be useful.) These fields encode which spatial dimension (1,2, or 3) corresponds to which acquisition dimension for MRI data.

Examples:
Rectangular scan multi-slice EPI:
freq_dim = 1 phase_dim = 2 slice_dim = 3 (or some permutation)
Spiral scan multi-slice EPI:
freq_dim = phase_dim = 0 slice_dim = 3 since the concepts of frequency- and phase-encoding directions don't apply to spiral scan.

The fields freq.dim, phase.dim, slice.dim are all squished into the single byte field dim.info (2 bits each, since the values for each field are limited to the range 0..3). This unpleasantness is due to lack of space in the 348 byte allowance.

See Also

fps2diminfo

Examples

dim.info <- f.read.header(system.file("example-nifti.hdr", package="AnalyzeFMRI"))$dim.info
diminfo2fps(dim.info)

AnalyzeFMRI documentation built on Oct. 5, 2021, 5:06 p.m.