A surprising use of 3D printing has been in creating life-like models of human body parts using MRI or CT scans. Surgeons and other medical professionals can use models to plan procedures or assist in research. However, there has been a problem. The body is a messy complex thing and there is a lot of data that comes out of a typical scan. Historically, someone had to manually identify structures on each slice — a very time-consuming process — or set a threshold value and hope for the best. A recent paper by a number of researchers around the globe shows how dithering scans can vastly improve results while also allowing for much faster processing times.
As an example, a traditional workflow to create a 3D printed foot model from scan data took over 30 hours to complete including a great deal of manual intervention. The new method produced a great model in less than an hour.
One thing the researchers note is that the technique should be easy to adopt since it uses all open source software and existing image processing algorithms. There are some limitations, though. There are several things that limit the resolution and can introduce inaccuracies. For example, MRI intensity versus actual tissue appearance is highly variable based on the scanning machine’s settings and operator.
The researchers also note that advances in scanning technology will make even better 3D printed models possible. Naturally though, these prints aren’t coming off a $150 hobby-grade printer. The Connex500 printer used costs a cool quarter of a million dollars. It can print up to 14 different materials in the same job and has a reasonably large build volume (500x400x200 mm). That price, however, doesn’t include the water station to wash away support material, so budget accordingly.
We couldn’t help but wonder if you will one day have a bad part of your body scanned, printed, and then you’ll get the new part to replace the old. It seems like if you have a model of a body part, it would be just a little math to print a perfect cast, brace, or splint, too. But, then again, we aren’t doctors.
Photo Credit: Steven Keating and Ahmed Hosny/Wyss Institute at Harvard University
How much does the ink cost to print a foot model and how long does the print take? How much is the water station?
The material is around 900USD/3.6kg and this print would probably be around 1.5kg (including the waste and support material). The water station was below 10k as far as I remember. The print time would probably be around 20hours. Source: Had an Objet Eden 260VS at my former workplace.
What does an hour of print time bill out at? 375 USD for just the material.
It depends… On complex and fragile parts cleaning is very time consuming which increases the cost heavily. I can’t tell how much an hour would cost since it depends on how good you maintain the machine. If you don’t do maintenance a head can clog easily. A replacement head costs around 1250USD. (There are 8 heads with 8 nozzles each in one machine)
I had some questions after reading this article, and I hope others will benefit from this post.
For example, to print the foot as described above:
1) Threshold and subtract all CT/Ultrasound/MRI data so that it removes air (easy). Now you’re left with the “data to print” (the foot).
2) Map remaining data (organic material density) so that it spans 0-100% (not too difficult)
3) use dithering to create infill data of your 2-head 3D printer (this is the novel bit).
4) Setup your had a printer with flexible transparent material and white PLA.
5) Print
2) Mapping
I assume the mapping should be linear, but it may not be.
For instance, if organic material of (2) is represented as raw MRI/CT/ultrasound data with raw data values of, say, 233 to 478, the algorithm could map from 0 to 100%.
The data set could determine how successful this step is in getting realistic looking prints.
3) Dithering
The Floyd-Rosenberg dithering will then convert the 0-100% data to print pixel of transparent material, OR print pixel of non-transparent material. You can get this plugin for programs such as paint.net
4) flexible transparent material:
https://www.youtube.com/watch?v=aSeOQgPLiIA
5) If the resolution is high enough, this would then create the right print. So in theory you could do this at home, if you can get your hands on the data set.
Oops: not Floyd-Rosenberg, but Floyd-Steinberg. Here’s a wiki article:
https://en.wikipedia.org/wiki/Floyd%E2%80%93Steinberg_dithering
How varied is CT/Ultrasound/MRI data? Same file formats?
If the data uses the DICOM file format, in theory it shouldn’t matter where the data comes from.
But the image source (CT/MRI) may have inherent differences that result in different mappings when they are used to represent for instance bone density. That is because CT and MRI measure different things when you want to see “the bone”.
BTW, you can freely download the ITK toolkit https://itk.org/Wiki/ITK, which is open source and widely used in academia to process DICOM images, and then segment them etc.
For instance: to open a DICOM image https://itk.org/ITKExamples/src/IO/GDCM/ReadDICOMSeriesAndWrite3DImage/Documentation.html
Thanks to Al Williams and to mime for followup :-)
I then interpret from the comparative success as above, it should be possible and at amateur level to print a rubber glove which appears as a human hand flexible enough to pull over prosthetic prototypes either transparent or not. Interested to see if anyone has such experience and direct links to forums looking into this ?
So far I can imagine a few interesting permutations which used to be on my back burner now foremost (eek) and could be the basis for an interesting and diverse project. I like to think this could be a great way for experimenters looking into robotic hands to add that extra touch ;-)
It’s not entirely clear what you want.
If you want to print only the skin as a glove of transparent material, then no, you can’t do this using the above. That is because you cannot separate the transparent layer from the rigid layer, because they are merged together.
Could you remap transparent to dissolvable support?
Perhaps what he could try is to keep transparent as transparent (the skin), but whenever there is solid (the bone), map that as dissolvable support as you suggest.
Some people have taken their CAT or MRI scan data home and printed their own 3D models then given them to the doctors as an aid in planning their operation. 3D model of hand bones made it easy for dr to see how they were damaged https://www.reaktor.com/blog/how-to-create-a-3d-print-of-your-own-bones/
Homebrew 3D print of brain tumor aids drs https://makezine.com/2015/01/14/hands-on-health-care/
So the basic current work flow is to take the MRI or CT data, work with radiologist to attain desired anatomy and define noise and other unwanted details with a technician to clean up later. The DICOM files are transferred to Materialize Mimics software which helps create the 3D file from all the slices and usually using a mix of Photoshop and Magics as well create the well defined 3d bodies to create an “Assembly” of Stls that will be loaded together in Objet studio or GragCAD print. The current flagship to do this process is far and away the Stratasys J750, which is their resin jetting unit that uses large inkjet heads to concurrently mix 6 materials with a soluble gel support in CMYKW and a clear or flexible for the 6th. This allows for clear outer tissue, vascular paths, bone, organs nerves etc all build into the same model/print. PS this is all cool and not cheap. Resin runs $330+ per liquid kg and that J750 is about $360,000 All in.
“It seems like if you have a model of a body part, it would be just a little math to print a perfect cast, brace, or splint, too. But, then again, we aren’t doctors.”
See: Invisalign
And I wonder why there are so many mis or really mal-diagnosis? HHhmmm… just like an attorney racket with an “educated guess” or “professional opinion” (yeah, of course you want to make money off slow murdering who ever you can and do whatever you want unless there is threat of liability or retaliation… wonder why amnesic drugs and narcotics are pushed so much) when there are six sigma validated systems proven to function in extreme environments people can’t even survive.
Someone needs to take the U.S. AMA , Bar Association and whatever U.N. treasonous war criminal traitors to military courts martial trial for practicing worse than Nazi Nursing and Medicine acting all innocent like they’re not committing death sentence able offenses. Including in remote sensing stations trying to remote communicate, brain wash, sonic assault, mind control and mass murder making everyone believe they’re telling the truth, including torturing people to believe. And I wonder why crime even exists? What a pan troglodyte industry trying to look smart pathetic archaic needing to go extinct like the evolutionary theory they preach and predators they are.
Awesome 3D prints… about time. No wonder Open Water Company is struggling with ethical issues. Pathetic U.N. inbreds form countries where you can marry your first cousin.
I saw this and immediately thought of West World.
Reading the paper – it looks like this is only really usable in resin or jet 3d printers.
Surely they convert regular models to raster layers when they slice already – rather than tool paths we’re used to in FDM.
Could be wrong but I can see how one could use this to create a manifold .stl.
Super cool though.