Lead Group Analyses

GROUP ANALYSES IN LEAD GROUP
LEAD-DBS WORKSHOP QUEENSLAND| FEB 2020 | Friederike Irmen

DBS imaging on a group level (Treu et al. 2020) -
S1 – Walkthrough Tutorial
friederike.irmen@charite.deLead-DBS Workshop
Group analyses in Lead-DBS

Sample
• 51 PD patients (age 60 ± 7.9; 17 female)
• Stimulation parameters
• Regressor: UPDRS-III ON vs. OFF DBS, OFF
Medication:
45.4 ± 23.0% improvement
 Is the improvement of motor symptoms related to
electrode location?

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andreas.horn@charite.deLead-DBS Workshop
1. Define a folder where to store the group analysis “model”
You can switch back and forth between Lead-DBS and Lead Group
This file is auto generated:
- All info stored in here
- more or less portable
project data, i.e. built to share
with colleagues
(restrictions apply)

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You can add patients to your group analysis

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You can assign subgroups if needed

Click group colors and choose preferred colors

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Click Review/Edit under Variables and enter values for each patient.
Note: alternatively, variables can be added more easily within Matlab, in the Lead
group file: M.clinical.vars

Under Stimulation
Parameters, specify active
contacts and amplitudes for
all patients
Select VTA model approach,
add amplitude
and cathodal/anodal contacts.

Select VTA model approach,
add amplitude
and cathodal/anodal contacts.

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You can enter up to 4 power sources each with
different amplitudes/active contacts
Color of contacts shows which source is
currently being programmed
same color
same color
Jump to next patient and after adding parameters for all patients click save

Stim params and Group colors buttons turn green if information has been stored in model

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Select atlas and “Visualize 3D” the selected patients

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You can select/deselect groups/electrodes to visualize

2D Visualization of electrodes as point
clouds, colored by group

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Select atlas and click “Visualize 2D”
Tune 2D visualization settings

2D slices of the most dorsal contacts in the left hemisphere
Light blue and light red colors represent poor vs. good responders, respectively and
dark blue vs. dark red circles depict the two patients with the least and most clinical benefit.
STN is shown in orange.
“Color by regressor”
This box can only be checked if Point-Clouds are selected.

a. Same setup as for Figure 2, now under 3D options
select Point-Clouds and press Visualize 3D
b. Together with the electrode scene, the slice control
figure pops up (bottom left), where the 7T template can
be chosen as background.
3D Visualization of electrodes as point
clouds, colored by group

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Select “Highlight Active Contacts” to mark active contacts in red

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Now you can specify also in 3D whether to show passive and/or active contacts and whether
to highlight active ones

Color point-cloud by regressor

In the function ea_showelectrode.m, the size of the Point-Clouds can be edited in
line 206-212 (e.g. ms=15)
In the viewer: Edit - Current Object Properties can be selected to e.g. the STN
edge color, transparency etc.
Good
responders
Poor
responders
Visualize groups separately

Map regressor as interpolated point mesh
a. Under Visualization Options check the box “Map
regressor to Coords”
b. Uncheck the box “Show Active Contacts”
c. In 3D options, same as for previous figure and
select “Visualize regressor as: Interpolated point
mesh”
“Visualize regressor as: isosurface”

Map regressor on VTA
Group
only left hemisphere
Single patient
only left hemisphere
Together with the plot, a window
appears, which allows to change the
threshold, alpha and smoothing of
the regressor
The output, provided for the left
hemisphere, can be found in the
group folder under statvat_results-
models

Mapping regressors in Lead group
electrode
coordinates as
interpolated
point mesh
point clouds
colored by
clinical
improvement
Visualize
regressor as
isosurface
VTAs of patients
weighted by
clinical
improvement
and thresholded
by a T-value of
10.56;

The “Target report” feature
• Calculate distance to a target
• Differentiate contacts that lie within the target
structure vs. outside it

Careful: Since it’s always the distance to the closest voxel of a
target, even if the electrode contact is in the middle of the
target structure, the distance to the shell of the target will be
listed. Thus, a visual check of the contact positions is
recommended!
Distance from each contact to the
closest (!) voxel of the target
structure
indicating whether each contact lies
“within” the target, based on a chosen
threshold.

For each active contact (highlighted in red), the distance from the contact center to the
STN is shown for patients with best (red) and worst (blue) clinical outcomes.

VTA intersections
Plots of the correlations and group comparisons can be generated under
“Explore Stats” – “Analyze Intersections with local structures”.
Depending on the chosen atlas under General settings, subcortical regions
can be chosen. Clinical variables/groups need to be selected, respectively.

VTA intersection with target structure
Correlation between clinical
improvement and intersections
between VTA and the STN.
Patients with best vs.
poorest responses are highlighted.
Patients were arbitrarily median-split into two
groups, based on their percentage
improvement. The group of better responders
(red) showed significantly higher VTA overlap
with the STN.

Here, the regions
available depend on
the selected brain
parcellation.
Correlations with connected stuctures
correlation/group comparison with fibercounts to
connected structures

Correlations with connected stuctures
Correlation with connectivity to cortical structures. The six structures of
the HMAT parcellation, colored by the R value, resulting from
Spearman’s rank-correlations between fibercounts to these areas and
clinical improvement.

Discriminative Fibers
• Under 3D settings, select
“Show discriminative fibers”
• Select whether
positive/negative/both fibers
should be visualized; select
threshold; you can also switch
to the E-field model

• “Visualize 3D” and the fibers
will be selected, which may
take a while when executed for
the first time.
• When finished, a control
window pops up, which allows
you to change the thresholds.

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Tracts that are positively associated with clinical
improvement are colored by their T-value
In the toolbar you’ll find “Add objects”, where you can add regions of
interest to the figure, like the HMAT parcellation in blue.

Lead Group Analyses

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