How I 3D Printed My Kidneys

So, the other week I was in the hospital for extreme abdominal pain. Turns out, after a CAT scan, I found out I had kidney stones. Worst pain I’ve ever felt.

On the plus side, I was able to ask the CT techs for the DICOM files! DICOM is a protocol that stands for Digital Imaging and Communications in Medicine, and this is what the CAT scan machine spits out.

What a CAT scan machine does is take an X-ray while moving the patient (me) and rotating the x-ray aperture (emitter) and corresponding sensors. The procedure took a couple of minutes, and the result was thousands of individual x-ray image “slices” from all different angles. Using clever maths, it’s possible to use those shots from multiple angles to determine the density of whatever is being imaged. In this case, it was my abdomen and kidneys. The darker areas shows are areas that did not absorb much radiation: skin, muscle, fat, etc. The lighter areas are areas that bounced back much of the radiation, namely my organs and bones.

The CT tech’s computer takes all of these individual slices, stitches them together, and creates a 3D model that they can analyze, and view in both 3D and 2D. The 2D slices generally correspond to the 3 planes of the body, Sagittal, Coronal, and Transverse, planes. Through these planes, they can pan back and forth through the body.

With those sliders, it’s possible to pan back and forth, through the body, looking at all sorts of different layers.

Now, the files the techs gave me were only 2D, so I used a program called 3D slicer. It can be found here: https://www.slicer.org/ . It is a very powerful program, allowing you to identify, or trace, over the individual slices. The end result is a 3D composite made from the individual slices. Here is what the output from 3d slicer looked like:

Note that there are a lot of lumps, ridges, and points, that are due to artifacts from the slicing process. I then put the raw .obj files and opened them up in Z-Brush. Z-Brush is a powerful and intuitive sculpting and modeling program, usually used for digital artists. With it, I was able to remove the many artifacts and smooth the kidney out to what it should look like:

I then opened up the .obj file in Slic3r (not to be confused with 3d slicer), added support material, and got the file ready to be printed. I exported it as gcode and got it ready to print!

 

Unfortunately I haven’t had a chance to actually print the kidneys, I’ve been too busy with work and school.

I plan to stop at Milwaukee Makespace this Tuesday, and I will upload the pictures of it as soon as the print is done!