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@agirault
Last active February 5, 2021 15:32
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import vtkImageMapper from 'vtk.js/Sources/Rendering/Core/ImageMapper';
import * as vtkMath from 'vtk.js/Sources/Common/Core/Math';
const { SlicingMode } = vtkImageMapper;
const ScreenSide = {
top: Symbol('top'),
bottom: Symbol('bottom'),
left: Symbol('left'),
right: Symbol('right'),
close: Symbol('close'),
far: Symbol('far'),
};
function LPSCoordinatesOfScreenSide(screenSide) {
switch (screenSide) {
case ScreenSide.top: return [0, -1, 0];
case ScreenSide.bottom: return [0, 1, 0];
case ScreenSide.left: return [-1, 0, 0];
case ScreenSide.right: return [1, 0, 0];
case ScreenSide.close: return [0, 0, -1];
case ScreenSide.far: return [0, 0, 1];
default: return [];
}
}
const Label = {
left: Symbol('Left'),
right: Symbol('Right'),
posterior: Symbol('Posterior'),
anterior: Symbol('Anterior'),
superior: Symbol('Superior'),
inferior: Symbol('Inferior'),
};
function LPSCoordinatesOfLabel(label) {
switch (label) {
case Label.left: return [1, 0, 0];
case Label.right: return [-1, 0, 0];
case Label.posterior: return [0, 1, 0];
case Label.anterior: return [0, -1, 0];
case Label.superior: return [0, 0, 1];
case Label.inferior: return [0, 0, -1];
default: return [];
}
}
function labelFor(screenSide, mapper) {
// Method for image space slicing (I, J, K)
function labelForImageSpaceSlicing(mat3x3) {
// Create a 3x3 matrix transformation from the image space
// (IJK, JKI or KIJ) to world space (LPS)
const dir9 = mapper.getInputData().getDirection();
const dir3x3 = [
[dir9[0], dir9[3], dir9[6]],
[dir9[1], dir9[4], dir9[7]],
[dir9[2], dir9[5], dir9[8]],
];
vtkMath.multiply3x3_mat3(dir3x3, mat3x3, mat3x3);
// Apply the transformation to the coordinate of the side
let outVec = [0, 0, 0];
const inVec = LPSCoordinatesOfScreenSide(screenSide);
vtkMath.multiply3x3_vect3(mat3x3, inVec, outVec);
// Restrict to the unit vectors
outVec = outVec.map((val) => {
const threshold = Math.sqrt(0.5);
if (val < -threshold) {
return -1;
}
if (val > threshold) {
return 1;
}
return 0;
});
// Find matching label
const labels = Object.values(Label);
return labels.find((label) => vtkMath.areMatricesEqual(outVec, LPSCoordinatesOfLabel(label)));
}
switch (mapper.getSlicingMode()) {
case SlicingMode.I: {
// JKI -> IJK
const mat3x3 = [[0, 1, 0], [0, 0, -1], [-1, 0, 0]];
return labelForImageSpaceSlicing(mat3x3);
}
case SlicingMode.J: {
// KIJ -> IJK
const mat3x3 = [[1, 0, 0], [0, 0, -1], [0, 1, 0]];
return labelForImageSpaceSlicing(mat3x3);
}
case SlicingMode.K: {
// IJK -> IJK
const mat3x3 = [[1, 0, 0], [0, 1, 0], [0, 0, 1]];
return labelForImageSpaceSlicing(mat3x3);
}
case SlicingMode.X:
switch (screenSide) {
case ScreenSide.top: return Label.superior;
case ScreenSide.bottom: return Label.inferior;
case ScreenSide.left: return Label.anterior;
case ScreenSide.right: return Label.posterior;
case ScreenSide.close: return Label.left;
case ScreenSide.far: return Label.right;
default: return null;
}
case SlicingMode.Y:
switch (side) {
case ScreenSide.top: return Label.superior;
case ScreenSide.bottom: return Label.inferior;
case ScreenSide.left: return Label.right;
case ScreenSide.right: return Label.left;
case ScreenSide.close: return Label.anterior;
case ScreenSide.far: return Label.posterior;
default: return null;
}
case SlicingMode.Z:
switch (screenSide) {
case ScreenSide.top: return Label.anterior;
case ScreenSide.bottom: return Label.posterior;
case ScreenSide.left: return Label.right;
case ScreenSide.right: return Label.left;
case ScreenSide.close: return Label.inferior;
case ScreenSide.far: return Label.superior;
default: return null;
}
default: return null;
}
}
export default {
ScreenSide,
labelFor,
};
@finetjul
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finetjul commented Feb 2, 2021

I find it odd that Side and LPSCoordinatesOfSide start with top/bottom but Label starts with left/right.

I also find odd that top is [0, -1, 0] and not [0, 1, 0]

@agirault
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agirault commented Feb 3, 2021

I find it odd that Side and LPSCoordinatesOfSide start with top/bottom but Label starts with left/right.

They're two distinct things though L/R for Side is left and right of the screen. L/R for Label is anatomical orientations. I don't think the order matters here since there isn't a 1-1 match.

I also find odd that top is [0, -1, 0] and not [0, 1, 0]

So, the logic here is a bit hard to explain (meaning I could do a better job/it should be refactored another way for clarity), but I'll try to show my thinking here: if you take a DICOM scan (IJ coordinates, slices along K) that is axial (direction cosines -> identity in LPS), then the top of the screen points to "Anterior" which is [0, -1, 0] in LPS.

It does work (I've tested with data acquired in any arbitrary direction), but I am pretty sure there is a better way to explain/implement the conversion from screen coordinates (Side) to anatomical coordinates (Label)

@finetjul
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finetjul commented Feb 3, 2021

Not sure to fully understand, but it seems that you know what you are doing :-)

As a side note, I did not realize that Side was for screen positions, maybe ScreenSide would be more meaningful...

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