Import MEG Data
This module imports MEG data and MEG coil array parameters and locations relative to the subject’s
head coordinate system.
Types of data imported:
4D Neuroimaging binary data from SUN SPARC Ultra 60 workstation
Generic binary data files created by other MEG systems or analysis software.
Generic ascii data created by other MEG systems or analysis software.
Data files and Sensor array coordinate files are described.
4D Neuroimaging utilities for automatic creation of data and sensor array descriptor files are provided.
This utility is used to import data into the MEG_tools program. The actual data file can be one of
1. 4D neuroimaging binary data (this is default import). This import utility is presently configured to
import 4D neuroimaging formatted data as created on SUN ulta60 workstations. These data are easily
transferred to the PC via ftp protocol.
2. Binary MEG/EEG data acquired with any other MEG system. (You must know the data format).
These must be stored as a sequence of data time slices rather than as sequential channels of data. The
type of MEG system is specified in a secondary configuration file, (gen_sen_loc.txt).
3. Data matrix in ASCII format with either rows or columns corresponding to the sequential time increments.
This format should only be used for small time segments of data such as evoked response data.
Auxiliary Data Description Files
Three additional MEG data description files are required. This program includes a set of utilities
to create these files for 4D neuroimaging data. However, for data imported from other MEG systems, a
different set of generic datafile formats has been developed.
4D Neuroimaging binary data, auxiliary files:
1. header.txt (channels id, location in time slice, and conversion factor to Tesla units).
2. sen_loc.txt (location and orientation of the sensors, electrodes in the subject coordinate system.)
3. hsfile.txt (location of nasion, left and right pre-auricular points and hundreds/ thousands of points
used to describe the full extent of the head geometry.)
The header, sen_loc, and hsfile are created by 4D helper functions implemented on the SUN ultra 60
workstation. We have automated the generation of these files by creating an executable UNIX script file,
“get_info”. After installing this file, the 4D Neuroimaging software creates a drop down menu option
that causes the header, sen_loc, and hsfile files to be produced for the "posted" data file on the SUN
workstation. These files and the 4D binary data file are transferred to the PC via ftp protocol. (SEE 4D
utilities folder README.TXT for installing and using this UNIX utility). This file is included with the
MEG_tools installation files. (Included with the MEG TOOLS for Matlab program are the 4D software
utilities that contain the “Get_MEG_tools_info” file and instructions to install it in the 4D Neuroimaging
Specifics of 4D utilities implemented in the “get_info” application:
4D helper function »> output file
convert »> header
print_hs_file »> hsfile
config_printer »> sen_loc
The output files are ASCII files that can be examined with WORDPAD or NOTEPAD etc. See examples
of these files in the DEMO DATA that can be downloaded with the MEG TOOLS for Matlab software.