Modifying position of the electrodes

[maria]

Hello Lead DBS Team!

I have a question regarding electrodes visualization. I am interested in modifying the position of the reconstructed electrodes on ELVIS. The CT image I have used for electrode reconstruction is from a different patient than from the T1 image, but just for visualisation purposes I would like to be able to move the electrodes to a desire target in the patient from the T1 image. I tried looking at the mat file ea_reconstruction.mat

>>reco.mni

struct with fields:

coords_mm: {[8×3 double] [8×3 double]}
markers: [1×2 struct]
trajectory: {[50×3 double] [50×3 double]}

I have tried to add a vector that would represent the translation as such to get a feel of how it could be done:

Electrode_2 = [0.5,0,0];

new_reco.mni.coords_mm{1,2} = reco.mni.coords_mm{1,2} + Electrode_2;
new_reco.mni.trajectory{1,2} = reco.mni.trajectory{1,2} + Electrode_2;

new_reco.mni.markers(2).head = reco.mni.markers(2).head + Electrode_2;
new_reco.mni.markers(2).tail = reco.mni.markers(2).tail + Electrode_2;
new_reco.mni.markers(2).x = reco.mni.markers(2).x + Electrode_2;
new_reco.mni.markers(2).y = reco.mni.markers(2).y + Electrode_2;

Which works fine, but I would need to make the head and the tail move indenpendently (let’s say tip [0,2,1], head [1.5 0 1]) However if I do that the electrode completely deforms. I have realised it is due to the variables new_reco.mni.markers(2).x and new_reco.mni.markers(2).y, however I am not sure what this two variable mean, and how to make them stay constant, since checking ea_elspec_boston_vercise_directed.m I saw that the model values are:

electrode.head_position = [0 0 0.75];
electrode.tail_position = [0 0 6.75];
electrode.x_position = [0.65 0 0.75];
electrode.y_position = [0 0.65 0.75];

but that doesn’t seem to remain constant after the electrode reconstruction ( subtracting head and tail or x and y in the reco.mni.markers doesn’t give similar results)

Is there a simpler way to modify the position of the electrodes to visualize in a specific coordinate I may choose? If not is my initial idea a good way to do it? or could I try something else? Also what is the meaning of the x and y components in reco.mni.markers?

>> reco.mni.markers.x

ans =

12.1513 -14.1638 -7.1217

ans =

-13.5965 -16.7858 -8.1650

>> reco.mni.markers.y

ans =

12.7529 -13.8990 -7.7418

ans =

-13.0312 -16.2178 -8.6009

>> reco.mni.markers.head

ans =

12.7658 -14.2935 -7.2394

ans =

-12.9903 -16.5855 -8.0724

>> reco.mni.markers.tail

ans =

14.6941 -8.9302 -3.0777

ans =

-15.4147 -11.0993 -4.0677

Thank you very much,

Maria

[Author]

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