How to move a 3D volume in 6D (3 Translations and 3 Rotations)

Hello everyone,

I am simulating a CT volume that includes a couple of different structures using the "createSyntheticSkullCT" function. After that, I generate X-ray projections from the CT volume.

My goal is to move this CT volume in 6D, which includes translation in millimeters (X, Y, Z) and rotation in degrees (roll, pitch, yaw). To achieve this, I defined a function called "applyRigidTransform3D" in code 1 and "rigidTransform6D" in code 2 for the 6D movements, but I am not sure if this function is working correctly.

I would greatly appreciate any insights or suggestions regarding this code. Is my simulation realistic? If not, which parts contain errors? I would also welcome any recommended validation or sanity checks.

I have attached the MATLAB codes (Code1.m and Code2.m) below for reference.

Thank you!

[Catalytic]

To achieve this, I defined a function called "applyRigidTransform3D" in code 1 and "rigidTransform6D" in code 2 for the 6D movements, but I am not sure if this function is working correctly.

Your posting style is unlikely to get responses because -

(1) You give us the entirety of your code even though your question is only about one specific part of the code, here applyRigidTransform3D. This forces readers to wade through unnecessary sections to get to the relevant part, which they are unlikely to do.

(2) You have presented no demonstration or test to show what makes you unsure whether the code is working.

Answer 1

[Matt J]

I defined a function called "applyRigidTransform3D" in code 1 and "rigidTransform6D" in code 2 for the 6D movements

It shouldn't be necessary to implement your own functions. These things already exist in Matlab in the form of imwarp and rigidtform3d.

[payam samadi]

Thank you.

I checked the functions imwarp and rigidtform3d and applied them to my data, but I encountered an issue.

For example, when I applied the following translation:

```matlab translation = [100, 0, 0]; % y, z, x % Translation in mm [LR, AP, SI] ```

and plotted the 3D moved CT to compare it with the original CT volume, it appears that no translation was applied!

Do you have any idea for this reasons?

[Matt J]

It's because you are using the default OutputView setting. Instead, you want,

tform = rigidtform3d(rotation,translation);

sameAsInput = affineOutputView(size(CT_volume),tform,"BoundsStyle","SameAsInput");

CT_moved = imwarp(CT_volume,tform,OutputView=sameAsInput);
volshow(CT_moved);