This page will teach you how to run an assessment of the accuracy of your HPI-digitization before entering the MSR
There are two main reasons why you would want to do this
Follow these simple steps: (be sure to run any commands exactly as shown):
./scripts/assess_hpi_digitization.sh
This script will allow you to check the accuracy of your digitization
This requires that you have digitized the HPI-coils again as the FIRST four ponts in your head shape digitization AND as the LAST four points in your head shape digitization
Press <ENTER> to continue!
## Default: current project chosen in Acqusition
Type in PROJECT name, EXACTLY as it is called in </neuro/data/sinuhe>
creating_a_black_hole
## Default: current subject chosen in Acqusition. It is possible to put in just the number, e.g. 0177
Type in SUBJECT name (format <NatMEG_****>, where **** is a 4-digit number
stephen_hawking
## Default: today's date
Type in DATE (format "YYMMDD", e.g. 160613 for June 13th 2016 ## if nothing is entered, today's date will be used as input
201231
## Default: dig_test.fif
Type in FILENAME of digitization test, default "dig_test.fif" ## if nothing is entered, "dig_test.fif" will be used as input
dig_test.fif
Press <ENTER> to start calculation!
Here’s some example output (again colouring is not relevant):
IGNORE THIS WARNING
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
This filename (/data/neuro-data/spatial_precision/MEG/NatMEG_0177/160613/dig_tes
t.fif) does not conform to MNE naming conventions. All raw files should end with
raw.fif, raw_sss.fif, raw_tsss.fif, raw.fif.gz, raw_sss.fif.gz or raw_tsss.fif.
gz
This file contains raw Internal Active Shielding data. It may be distorted. Elek
ta recommends it be run through MaxFilter to produce reliable results. Consider
closing the file and running MaxFilter on the data.
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
IGNORE THIS WARNING
DISTANCE BETEWEEN HPI AND FIRST FOUR CONTROL POINTS
-----------------------------------------------------------------------------
Distance between HPI-digitization no. 1 and control point no. 1 is: -33 mm
Distance between HPI-digitization no. 2 and control point no. 2 is: -0.8 mm
Distance between HPI-digitization no. 3 and control point no. 3 is: -23.8 mm
Distance between HPI-digitization no. 4 and control point no. 4 is: 19.2 mm
DISTANCE BETEWEEN HPI AND LAST FOUR CONTROL POINTS
-----------------------------------------------------------------------------
Distance between HPI-digitization no. 1 and control point no. 1 is: -66.8 mm
Distance between HPI-digitization no. 2 and control point no. 2 is: -14.5 mm
Distance between HPI-digitization no. 3 and control point no. 3 is: 20.4 mm
Distance between HPI-digitization no. 4 and control point no. 4 is: 204.6 mm
This suggests some pretty serious errors, (maybe the Polhemus on the forehead was moved or a black hole was created) and you should redo the digitization