How to get a voxel array from a list of 3D points that make up a line in a voxalized volume?
I ended up solving this problem myself. For anyone who is wondering how, I'll explain it briefly. 
First, since all the catheters point in the general direction of the z-axis, I got the thickness of the slices along that axis. Both input points land on a slice. I then got the coordinates of every intersection between the line between the two input points and the z-slices. Next, since I know the radius of the catheter and I can calculate the angle between the two points, I was able to draw ellipse paths on each slice around the points I had previously found (when you cut a cone at and angle, the cross-section is an ellipse). Then I got the coordinates of all the voxels on every slice along the z-axis and checked which voxels where within my ellipse paths. Those voxels are the ones that describe the volume of the catheter. If you would like to see my code please let me know.
I have a list of points that represent a needle/catheter in a 3D volume. This volume is voxalized. I want to get all the voxels that the line that connects the point intersects. The line needs to go through all the points. 
Ideally, since the round needle/catheter has a width I would like to be able to get the voxels that intersect the actual three dimensional object that is the needle/catheter. (I imagine this is much harder so if I could get an answer to the first problem I would be very happy!)
I am using the latest version of Anaconda (Python 3.7). I have seen some similar problems, but the code is always in C++ and none of it seems to be what I'm looking for. I am fairly certain that I need to use raycasting or a 3D Bresenham algorithm, but I don't know how. 
I would appreciate your help!