Step 14. Make Hardcopy With GraphicsClipboard
Source Localization Tutorial
The intent of this tutorial is to give the MEG user a step by step introduction to the use of UUMSI's
Elekta Neuromag Source localization software applications. A sample dataset and MRI image are included.
Refer to the Xfit Users manual for greater details.
Step 1. Login To The Computer
Username: Your research group name.
Password: Your research group password.
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Step 2. Start the Application SourceModeling
On the Desktop click on the icon SourceModeling to open this window.
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Step 3. Open the Dipole Estimation
In Source Modeling in Menu-Estimate select Dipole Estimation. Note the parameters listed
across the top window. This is the time, location and quality data for the fitted dipoles.
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Step 4. Open the Application MriLab
In Fitting Estimation Menu click File and select Open MRILab.
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Step 5. Open an Mri Image
In MRILab click on menu File. Change the directory to /meg/research/tutorial/tutorial_a/mri/sets/left_somatosensory.fif and click on it.
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Step 6. Import Isotrak Data
Retrieve the head dimensions from the pre screen digitizing in MRILab.
Click Menu-File-Import and select Isotrak data. This data is held in the MEG scan data
file. Change the directory to /meg/research/tutorial/tutorial_a/left_somatosensory.fif
and click on it.
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Step 7. Open a Data File
On the menu click File. Click the ".." repeatedly to get to the /meg directory. Move through to
/meg/research/tutorial/tutorial_a/left_somatosensory.fif and open this file.
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Step 8. Open the Full View
Click on Menu-View and then select Full View. This opens the Xplot window and displays all
signals and their 2D relative locations. In this Xplot window click on the Scale button
to resize the signals. A left mouse click on any signal will display it back in the
Source Modeling - Signal Waveform window. This allows you to choose a signal of interest.
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Step 9. Filter the Average Signal
In Source Modeling click Menu-Process and select Filter. Click on the left side square
buttons to enable a filter type. The goal is to amplify the peak of interest and remove noise.
The Lowpass filter removes the higher frequency components, the Highpass filter will the remove lower
frequency components. The Notch filters are combinations of High and Low pass that can remove
specific frequencies that may be caused by artefacts. As you adjust these the resulting signal
will appear in the Filtered Response window.
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Step 10. Sequential Single Dipole Fit
In Fitting Estimation Menu click on Fit and select Sequential Dipole Fit. This is an automated
dipole fitting routine that will step through the averaged signal at user specified intervals. It
will calculate the best fit dipole at each interval. This is a broad technique for finding dipoles.
It will result in a series of both good and bad results. The time interval size has to aspects. The larger the interval the faster the calculation takes. However some good dipoles may be missed.
For this tutorial set the Start time to 0, the End Time to 800 and the interval to 10.
Then click on the Fit button.
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When the Sequential Single Dipole Fit is complete the dipole data will be displayed in
Dipole Estimation upper window.
Dipole Fit Parameters Defined
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Step 11. View the Dipole Locations
To view the dipole locations first highlight all the dipole data. Mouse left click the first line, scroll down to the last line and mouse left click. Mouse right button over the selected data will bring up a menu.
Select View Selections.
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Step 12.Filter From the List
The list can now be filtered using the dipole data. Mouse right button over the highlighted lines.
Select Filter. Click on the g > (%) button and enter 60.
Click on the Conf. volume < (mm^3) button and enter 600. Click on O.K.
The results are in the lower window. Mouse right button over the filtered list
to view them.
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Step 13. Move Dipole to MRI
In Dipole Estimation mouse right button open the filtered dipole data in the lower window. A menu appears, in it select Print -> Mri. The dipoles now marked on the MRI image.
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Step 14. Make Hardcopy with Application GraphicsClipboard
From the desktop start the application GraphicsClipboard. In the page setup window click the Apply button.
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The images in the other windows can be mouse dragged into the Graphicsclipboard. The method is unique
for Xplot. In Xplot middle mouse button and hold on the bottom right menu. Then hold the button down and
drag the image into one the GraphicClipboard windows. For all others, (Dipole Viewer, MRILab, and Source Modeling) the middle mouse button will drag the image to move. Select an image from each and drag into
GraphicsClipboard. The images can be printed by clicking Menu - File - Print. Select the printer FBI_color.
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